Add copycat-avro and copycat-runtime

build.gradle

@@ -33,6 +33,7 @@ allprojects {
   apply plugin: 'idea'
   repositories {
     mavenCentral()
+    mavenLocal() // FIXME Currently required to get io.confluent:kafka-avro-serializer:2.0-SNAPSHOT
   }
 }
 
@@ -239,7 +240,7 @@ project(':core') {
     }
 
     testCompile 'junit:junit:4.6'
-    testCompile 'org.easymock:easymock:3.0'
+    testCompile 'org.easymock:easymock:3.3.1'
     testCompile 'org.objenesis:objenesis:1.2'
     testCompile "org.scalatest:scalatest_$baseScalaVersion:2.2.5"
 
@@ -514,7 +515,7 @@ project(':copycat-api') {
   }
 
   javadoc {
-    include "**/org/apache/kafka/copycat/api/*"
+    include "**/org/apache/kafka/copycat/*"
   }
 
   artifacts {
@@ -525,9 +526,103 @@ project(':copycat-api') {
     archives.extendsFrom (testCompile)
   }
 
-  /* FIXME
   checkstyle {
     configFile = new File(rootDir, "checkstyle/checkstyle.xml")
   }
-  test.dependsOn('checkstyleMain', 'checkstyleTest') */
+  test.dependsOn('checkstyleMain', 'checkstyleTest')
+}
+
+project(':copycat-avro') {
+  apply plugin: 'checkstyle'
+  archivesBaseName = "copycat-avro"
+
+  dependencies {
+    compile project(':copycat-api')
+    compile "org.slf4j:slf4j-api:1.7.6"
+    compile "io.confluent:kafka-avro-serializer:2.0-SNAPSHOT"
+
+    testCompile 'junit:junit:4.6'
+    testCompile 'org.easymock:easymock:3.3.1'
+    testCompile 'org.powermock:powermock-module-junit4:1.6.2'
+    testCompile 'org.powermock:powermock-api-easymock:1.6.2'
+    testRuntime "$slf4jlog4j"
+  }
+
+  task testJar(type: Jar) {
+    classifier = 'test'
+    from sourceSets.test.output
+  }
+
+  test {
+    testLogging {
+      events "passed", "skipped", "failed"
+      exceptionFormat = 'full'
+    }
+  }
+
+  javadoc {
+    include "**/org/apache/kafka/copycat/*"
+  }
+
+  artifacts {
+    archives testJar
+  }
+
+  configurations {
+    archives.extendsFrom(testCompile)
+  }
+
+  checkstyle {
+    configFile = new File(rootDir, "checkstyle/checkstyle.xml")
+  }
+  test.dependsOn('checkstyleMain', 'checkstyleTest')
+}
+
+project(':copycat-runtime') {
+  apply plugin: 'checkstyle'
+  archivesBaseName = "copycat-runtime"
+
+  dependencies {
+    compile project(':copycat-api')
+    compile project(':copycat-avro')
+    compile project(':clients')
+    compile "org.slf4j:slf4j-api:1.7.6"
+    // FIXME we shouldn't depend on core since we only need clients, but currently we're doing sink task topic-partition assignment manually until we switch over to new consumer group functionality
+    compile project(':core')
+
+    testCompile 'junit:junit:4.6'
+    testCompile 'org.easymock:easymock:3.3.1'
+    testCompile 'org.powermock:powermock-module-junit4:1.6.2'
+    testCompile 'org.powermock:powermock-api-easymock:1.6.2'
+    testRuntime "$slf4jlog4j"
+  }
+
+  task testJar(type: Jar) {
+    classifier = 'test'
+    from sourceSets.test.output
+  }
+
+  test {
+    testLogging {
+      events "passed", "skipped", "failed"
+      exceptionFormat = 'full'
+    }
+  }
+
+  javadoc {
+    include "**/org/apache/kafka/copycat/*"
+  }
+
+  artifacts {
+    archives testJar
+  }
+
+  configurations {
+    archives.extendsFrom(testCompile)
+  }
+
+  checkstyle {
+    configFile = new File(rootDir, "checkstyle/checkstyle.xml")
+  }
+  test.dependsOn('checkstyleMain', 'checkstyleTest')
 }

checkstyle/import-control.xml

@@ -119,6 +119,49 @@
 			<allow pkg="org.apache.kafka.copycat.connector" />
 			<allow pkg="org.apache.kafka.copycat.storage" />
 		</subpackage>
+
+		<subpackage name="avro">
+			<allow pkg="org.apache.avro" />
+			<allow pkg="org.apache.kafka.copycat" />
+			<!-- FIXME/move Avro plugin out of Kafka -->
+			<allow pkg="io.confluent.kafka.serializers" />
+			<allow pkg="io.confluent.kafka.schemaregistry" />
+		</subpackage>
+
+		<subpackage name="runtime">
+			<allow pkg="org.apache.kafka.copycat" />
+			<allow pkg="org.apache.kafka.common" />
+			<allow pkg="org.apache.kafka.clients" />
+			<!-- for tests -->
+			<allow pkg="org.easymock" />
+			<allow pkg="org.powermock" />
+
+			<!-- FIXME Remove when dependency on core for sink partition assignment is removed -->
+			<allow pkg="kafka.utils" />
+			<allow pkg="org.I0Itec.zkclient" />
+		</subpackage>
+
+		<subpackage name="cli">
+			<allow pkg="org.apache.kafka.copycat.runtime" />
+			<allow pkg="org.apache.kafka.copycat.util" />
+			<allow pkg="org.apache.kafka.common" />
+		</subpackage>
+
+		<subpackage name="storage">
+			<allow pkg="org.apache.kafka.copycat" />
+			<!-- for tests -->
+			<allow pkg="org.easymock" />
+			<allow pkg="org.powermock" />
+		</subpackage>
+
+		<subpackage name="util">
+			<allow pkg="org.apache.kafka.copycat" />
+
+			<!-- FIXME Remove when dependency on core for sink partition assignment is removed -->
+			<allow pkg="kafka.utils" />
+			<allow pkg="org.I0Itec.zkclient" />
+			<allow pkg="scala" />
+		</subpackage>
 	</subpackage>
 
 </import-control>

copycat-avro/src/main/java/org/apache/kafka/copycat/avro/AvroConverter.java

@@ -0,0 +1,35 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.avro;
+
+import org.apache.kafka.copycat.storage.Converter;
+
+/**
+ * Implementation of Converter that uses Avro schemas and objects.
+ */
+public class AvroConverter implements Converter {
+    @Override
+    public Object fromCopycatData(Object value) {
+        return AvroData.convertToAvro(value);
+    }
+
+    @Override
+    public Object toCopycatData(Object value) {
+        return AvroData.convertFromAvro(value);
+    }
+}

copycat-avro/src/main/java/org/apache/kafka/copycat/avro/AvroData.java

@@ -0,0 +1,350 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.avro;
+
+import org.apache.avro.generic.GenericDatumReader;
+import org.apache.avro.generic.GenericDatumWriter;
+import org.apache.avro.io.*;
+import org.apache.kafka.copycat.data.GenericRecord;
+import org.apache.kafka.copycat.data.GenericRecordBuilder;
+import org.apache.kafka.copycat.data.Schema;
+import org.apache.kafka.copycat.data.SchemaBuilder;
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.*;
+
+/**
+ * Utilities for converting between our runtime data format and Avro, and (de)serializing that data.
+ */
+public class AvroData {
+    private static final Map<String, org.apache.avro.Schema> PRIMITIVE_SCHEMAS;
+
+    static {
+        org.apache.avro.Schema.Parser parser = new org.apache.avro.Schema.Parser();
+        PRIMITIVE_SCHEMAS = new HashMap<String, org.apache.avro.Schema>();
+        PRIMITIVE_SCHEMAS.put("Null", createPrimitiveSchema(parser, "null"));
+        PRIMITIVE_SCHEMAS.put("Boolean", createPrimitiveSchema(parser, "boolean"));
+        PRIMITIVE_SCHEMAS.put("Integer", createPrimitiveSchema(parser, "int"));
+        PRIMITIVE_SCHEMAS.put("Long", createPrimitiveSchema(parser, "long"));
+        PRIMITIVE_SCHEMAS.put("Float", createPrimitiveSchema(parser, "float"));
+        PRIMITIVE_SCHEMAS.put("Double", createPrimitiveSchema(parser, "double"));
+        PRIMITIVE_SCHEMAS.put("String", createPrimitiveSchema(parser, "string"));
+        PRIMITIVE_SCHEMAS.put("Bytes", createPrimitiveSchema(parser, "bytes"));
+    }
+
+    private static final EncoderFactory ENCODER_FACTORY = EncoderFactory.get();
+    private static final DecoderFactory DECODER_FACTORY = DecoderFactory.get();
+
+    /**
+     * Convert this object, in the org.apache.kafka.copycat.data format, into an Avro object.
+     */
+    public static Object convertToAvro(Object value) {
+        if (value == null || value instanceof Byte || value instanceof Short ||
+                value instanceof Integer || value instanceof Long ||
+                value instanceof Float || value instanceof Double ||
+                value instanceof Boolean ||
+                value instanceof byte[] || value instanceof ByteBuffer ||
+                value instanceof CharSequence) {
+            // Note that using CharSequence allows Utf8 -- either copycat or Avro variants -- to pass
+            // through, but this should be fine as long as they are always handled as CharSequences
+            return value;
+        } else if (value instanceof GenericRecord) {
+            GenericRecord recordValue = (GenericRecord) value;
+            org.apache.avro.Schema avroSchema = asAvroSchema(recordValue.getSchema());
+            org.apache.avro.generic.GenericRecordBuilder builder
+                    = new org.apache.avro.generic.GenericRecordBuilder(avroSchema);
+            for (Schema.Field field : recordValue.getSchema().getFields()) {
+                builder.set(field.name(), convertToAvro(recordValue.get(field.name())));
+            }
+            return builder.build();
+        } else if (value instanceof Collection) {
+            Collection collection = (Collection) value;
+            List<Object> converted = new ArrayList<Object>(collection.size());
+            for (Object elem : collection) {
+                converted.add(convertToAvro(elem));
+            }
+            return converted;
+        } else if (value instanceof Map) {
+            Map<String, Object> map = (Map<String, Object>) value;
+            Map<String, Object> converted = new TreeMap<String, Object>();
+            for (Map.Entry<String, Object> entry : map.entrySet()) {
+                converted.put(entry.getKey(), convertToAvro(entry.getValue()));
+            }
+            return converted;
+        }
+        // Fixed and enum are handled by byte[] and String
+
+        throw new RuntimeException("Couldn't convert " + value + " to Avro.");
+    }
+
+    /**
+     * Serialize this object, in org.apache.kafka.copycat.data format, to Avro's binary encoding
+     */
+    public static ByteBuffer serializeToAvro(Object value) {
+        Object asAvro = convertToAvro(value);
+
+        if (value == null) {
+            return null;
+        }
+
+        try {
+            org.apache.avro.Schema schema = getSchema(asAvro);
+            ByteArrayOutputStream out = new ByteArrayOutputStream();
+            BinaryEncoder encoder = ENCODER_FACTORY.directBinaryEncoder(out, null);
+            DatumWriter<Object> writer;
+            writer = new GenericDatumWriter<Object>(schema);
+            writer.write(asAvro, encoder);
+            encoder.flush();
+            return ByteBuffer.wrap(out.toByteArray());
+        } catch (IOException e) {
+            throw new CopycatRuntimeException("Couldn't serialize object to Avro", e);
+        }
+    }
+
+
+    /**
+     * Convert the given object, in Avro format, into an org.apache.kafka.copycat.data object.
+     */
+    public static Object convertFromAvro(Object value) {
+        if (value == null || value instanceof Byte || value instanceof Short ||
+                value instanceof Integer || value instanceof Long ||
+                value instanceof Float || value instanceof Double ||
+                value instanceof Boolean ||
+                value instanceof byte[] || value instanceof ByteBuffer) {
+            return value;
+        } else if (value instanceof CharSequence) {
+            // We need to be careful about CharSequences. This could be a String or a Utf8. If we passed
+            // Utf8 values directly through using Avro's implementation, equality wouldn't work.
+            if (value instanceof org.apache.avro.util.Utf8) {
+                return value.toString();
+            } else {
+                return value;
+            }
+        } else if (value instanceof org.apache.avro.generic.GenericRecord) {
+            org.apache.avro.generic.GenericRecord recordValue
+                    = (org.apache.avro.generic.GenericRecord) value;
+            Schema copycatSchema = asCopycatSchema(recordValue.getSchema());
+            GenericRecordBuilder builder = new GenericRecordBuilder(copycatSchema);
+            for (org.apache.avro.Schema.Field field : recordValue.getSchema().getFields()) {
+                builder.set(field.name(), convertFromAvro(recordValue.get(field.name())));
+            }
+            return builder.build();
+        } else if (value instanceof Collection) {
+            Collection collection = (Collection) value;
+            List<Object> converted = new ArrayList<Object>(collection.size());
+            for (Object elem : collection) {
+                converted.add(convertFromAvro(elem));
+            }
+            return converted;
+        } else if (value instanceof Map) {
+            Map<String, Object> map = (Map<String, Object>) value;
+            Map<String, Object> converted = new TreeMap<String, Object>();
+            for (Map.Entry<String, Object> entry : map.entrySet()) {
+                converted.put(entry.getKey(), convertFromAvro(entry.getValue()));
+            }
+            return converted;
+        }
+        // Fixed and enum are handled by byte[] and String
+
+        throw new RuntimeException("Couldn't convert " + value + " from Avro.");
+    }
+
+    /**
+     * Deserialize and convert the provided binary Avro-serialized bytes into
+     * org.apache.kafka.copycat.data format.
+     */
+    public static Object deserializeFromAvro(ByteBuffer serialized, Schema schema) {
+        org.apache.avro.Schema avroSchema = asAvroSchema(schema);
+        DatumReader reader = new GenericDatumReader(avroSchema);
+        try {
+            Object deserialized =
+                    reader.read(null, DECODER_FACTORY.binaryDecoder(serialized.array(), null));
+            return convertFromAvro(deserialized);
+        } catch (IOException e) {
+            throw new CopycatRuntimeException("Couldn't deserialize object from Avro", e);
+        }
+    }
+
+
+    private static org.apache.avro.Schema createPrimitiveSchema(
+            org.apache.avro.Schema.Parser parser, String type) {
+        String schemaString = String.format("{\"type\" : \"%s\"}", type);
+        return parser.parse(schemaString);
+    }
+
+    private static org.apache.avro.Schema getSchema(Object object) {
+        if (object == null) {
+            return PRIMITIVE_SCHEMAS.get("Null");
+        } else if (object instanceof Boolean) {
+            return PRIMITIVE_SCHEMAS.get("Boolean");
+        } else if (object instanceof Integer) {
+            return PRIMITIVE_SCHEMAS.get("Integer");
+        } else if (object instanceof Long) {
+            return PRIMITIVE_SCHEMAS.get("Long");
+        } else if (object instanceof Float) {
+            return PRIMITIVE_SCHEMAS.get("Float");
+        } else if (object instanceof Double) {
+            return PRIMITIVE_SCHEMAS.get("Double");
+        } else if (object instanceof CharSequence) {
+            return PRIMITIVE_SCHEMAS.get("String");
+        } else if (object instanceof byte[] || object instanceof ByteBuffer) {
+            return PRIMITIVE_SCHEMAS.get("Bytes");
+        } else if (object instanceof org.apache.avro.generic.GenericContainer) {
+            return ((org.apache.avro.generic.GenericContainer) object).getSchema();
+        } else {
+            throw new IllegalArgumentException(
+                    "Unsupported Avro type: " + object.getClass());
+        }
+    }
+
+
+    // Implementation note -- I considered trying to unify asAvroSchema and asCopycatSchema through
+    // a generic implementation. In practice this probably won't be worth the relatively minor
+    // amount of code duplication avoided since a) the generic version is messy and b) the Copycat
+    // type system and Avro type system are likely to diverge anyway, which would eventually
+    // require splitting them up.
+
+    public static org.apache.avro.Schema asAvroSchema(Schema schema) {
+        switch (schema.getType()) {
+            case BOOLEAN:
+                return org.apache.avro.SchemaBuilder.builder().booleanType();
+            case BYTES:
+                return org.apache.avro.SchemaBuilder.builder().bytesType();
+            case DOUBLE:
+                return org.apache.avro.SchemaBuilder.builder().doubleType();
+            case FLOAT:
+                return org.apache.avro.SchemaBuilder.builder().floatType();
+            case INT:
+                return org.apache.avro.SchemaBuilder.builder().intType();
+            case LONG:
+                return org.apache.avro.SchemaBuilder.builder().longType();
+            case NULL:
+                return org.apache.avro.SchemaBuilder.builder().nullType();
+            case STRING:
+                return org.apache.avro.SchemaBuilder.builder().stringType();
+
+            case RECORD: {
+                List<org.apache.avro.Schema.Field> fields = new ArrayList<org.apache.avro.Schema.Field>();
+                for (Schema.Field field : schema.getFields()) {
+                    // NOTE: Order ignored
+                    // TODO: Providing a default value would require translating since Avro's is a JsonNode
+                    fields.add(new org.apache.avro.Schema.Field(
+                            field.name(), asAvroSchema(field.schema()), field.doc(), null));
+                }
+
+                org.apache.avro.Schema result = org.apache.avro.Schema.createRecord(
+                        schema.getName(), schema.getDoc(), schema.getNamespace(), schema.isError());
+                result.setFields(fields);
+                return result;
+            }
+
+            case UNION: {
+                List<org.apache.avro.Schema> unionTypes = new ArrayList<org.apache.avro.Schema>();
+                for (Schema origType : schema.getTypes()) {
+                    unionTypes.add(asAvroSchema(origType));
+                }
+                return org.apache.avro.Schema.createUnion(unionTypes);
+            }
+
+            case ARRAY:
+                return org.apache.avro.Schema.createArray(asAvroSchema(schema.getElementType()));
+
+            case ENUM:
+                return org.apache.avro.Schema.createEnum(schema.getName(), schema.getDoc(), schema
+                        .getNamespace(), schema.getEnumSymbols());
+
+            case FIXED:
+                return org.apache.avro.Schema.createFixed(schema.getName(), schema.getDoc(), schema
+                        .getNamespace(), schema.getFixedSize());
+
+            case MAP:
+                return org.apache.avro.Schema.createMap(asAvroSchema(schema.getValueType()));
+
+            default:
+                throw new CopycatRuntimeException("Couldn't translate unsupported schema type "
+                        + schema.getType().getName() + ".");
+        }
+    }
+
+
+    public static Schema asCopycatSchema(org.apache.avro.Schema schema) {
+        switch (schema.getType()) {
+            case BOOLEAN:
+                return SchemaBuilder.builder().booleanType();
+            case BYTES:
+                return SchemaBuilder.builder().bytesType();
+            case DOUBLE:
+                return SchemaBuilder.builder().doubleType();
+            case FLOAT:
+                return SchemaBuilder.builder().floatType();
+            case INT:
+                return SchemaBuilder.builder().intType();
+            case LONG:
+                return SchemaBuilder.builder().longType();
+            case NULL:
+                return SchemaBuilder.builder().nullType();
+            case STRING:
+                return SchemaBuilder.builder().stringType();
+
+            case RECORD: {
+                List<Schema.Field> fields = new ArrayList<Schema.Field>();
+                for (org.apache.avro.Schema.Field field : schema.getFields()) {
+                    // NOTE: Order ignored
+                    // TODO: Providing a default value would require translating since Avro's is a JsonNode
+                    fields.add(new Schema.Field(
+                            field.name(), asCopycatSchema(field.schema()), field.doc(), null));
+                }
+
+                Schema result = Schema.createRecord(
+                        schema.getName(), schema.getDoc(), schema.getNamespace(), schema.isError());
+                result.setFields(fields);
+                return result;
+            }
+
+            case UNION: {
+                List<Schema> unionTypes = new ArrayList<Schema>();
+                for (org.apache.avro.Schema origType : schema.getTypes()) {
+                    unionTypes.add(asCopycatSchema(origType));
+                }
+                return Schema.createUnion(unionTypes);
+            }
+
+            case ARRAY:
+                return Schema.createArray(asCopycatSchema(schema.getElementType()));
+
+            case ENUM:
+                return Schema.createEnum(schema.getName(), schema.getDoc(), schema
+                        .getNamespace(), schema.getEnumSymbols());
+
+            case FIXED:
+                return Schema.createFixed(schema.getName(), schema.getDoc(), schema
+                        .getNamespace(), schema.getFixedSize());
+
+            case MAP:
+                return Schema.createMap(asCopycatSchema(schema.getValueType()));
+
+            default:
+                throw new CopycatRuntimeException("Couldn't translate unsupported schema type "
+                        + schema.getType().getName() + ".");
+        }
+    }
+
+}

copycat-avro/src/main/java/org/apache/kafka/copycat/avro/AvroDeserializer.java

@@ -0,0 +1,50 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.avro;
+
+import io.confluent.kafka.serializers.AbstractKafkaAvroDeserializer;
+import io.confluent.kafka.serializers.KafkaAvroDeserializerConfig;
+import org.apache.kafka.copycat.data.Schema;
+import org.apache.kafka.copycat.storage.OffsetDeserializer;
+
+import java.util.Map;
+
+public class AvroDeserializer extends AbstractKafkaAvroDeserializer implements OffsetDeserializer<Object> {
+
+    @Override
+    public void configure(Map<String, ?> configs, boolean isKey) {
+        configure(new KafkaAvroDeserializerConfig(configs));
+    }
+
+    @Override
+    public Object deserializeOffset(String connector, byte[] data) {
+        // TODO: Support schema projection
+        return deserialize(data);
+    }
+
+    @Override
+    public Object deserializeOffset(String connector, byte[] data, Schema schema) {
+        // TODO: Support schema projection
+        return deserialize(data);
+    }
+
+    @Override
+    public void close() {
+
+    }
+}

copycat-avro/src/main/java/org/apache/kafka/copycat/avro/AvroSerializer.java

@@ -0,0 +1,66 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.avro;
+
+import io.confluent.kafka.schemaregistry.client.CachedSchemaRegistryClient;
+import io.confluent.kafka.serializers.AbstractKafkaAvroSerDeConfig;
+import io.confluent.kafka.serializers.AbstractKafkaAvroSerializer;
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.apache.kafka.copycat.storage.OffsetSerializer;
+
+import java.util.Map;
+
+public class AvroSerializer extends AbstractKafkaAvroSerializer implements OffsetSerializer<Object> {
+
+    private boolean isKey;
+
+
+    @Override
+    public void configure(Map<String, ?> configs, boolean isKey) {
+        this.isKey = isKey;
+        Object url = configs.get(AbstractKafkaAvroSerDeConfig.SCHEMA_REGISTRY_URL_CONFIG);
+        if (url == null) {
+            throw new CopycatRuntimeException("Missing Schema registry url!");
+        }
+        Object maxSchemaObject = configs.get(
+                AbstractKafkaAvroSerDeConfig.MAX_SCHEMAS_PER_SUBJECT_CONFIG);
+        if (maxSchemaObject == null) {
+            schemaRegistry = new CachedSchemaRegistryClient(
+                    (String) url, AbstractKafkaAvroSerDeConfig.MAX_SCHEMAS_PER_SUBJECT_DEFAULT);
+        } else {
+            schemaRegistry = new CachedSchemaRegistryClient(
+                    (String) url, (Integer) maxSchemaObject);
+        }
+    }
+
+    @Override
+    public byte[] serializeOffset(String connector, Object data) {
+        String subject;
+        if (isKey) {
+            subject = connector + "-key";
+        } else {
+            subject = connector + "-value";
+        }
+        return serializeImpl(subject, data);
+    }
+
+    @Override
+    public void close() {
+
+    }
+}

copycat-avro/src/test/java/org/apache/kafka/copycat/avro/AvroDataToAvroTest.java

@@ -0,0 +1,154 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.avro;
+
+import org.apache.kafka.copycat.data.GenericRecord;
+import org.apache.kafka.copycat.data.GenericRecordBuilder;
+import org.apache.kafka.copycat.data.Schema;
+import org.apache.kafka.copycat.data.SchemaBuilder;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.Collections;
+
+import static org.junit.Assert.*;
+
+// Tests AvroData's conversion of Copycat -> Avro
+public class AvroDataToAvroTest {
+
+    // All the primitive types are pass-through
+
+    @Test
+    public void testNull() {
+        assertNull(AvroData.convertToAvro(null));
+    }
+
+    @Test
+    public void testBoolean() {
+        Assert.assertEquals(true, AvroData.convertToAvro(true));
+    }
+
+    @Test
+    public void testInteger() {
+        Assert.assertEquals(12, AvroData.convertToAvro(12));
+    }
+
+    @Test
+    public void testLong() {
+        Assert.assertEquals(12L, AvroData.convertToAvro(12L));
+    }
+
+    @Test
+    public void testFloat() {
+        Assert.assertEquals(12.2f, AvroData.convertToAvro(12.2f));
+    }
+
+    @Test
+    public void testDouble() {
+        Assert.assertEquals(12.2, AvroData.convertToAvro(12.2));
+    }
+
+    @Test
+    public void testBytes() {
+        Object converted = AvroData.convertToAvro("foo".getBytes());
+        assertTrue(converted instanceof byte[]);
+        assertEquals(ByteBuffer.wrap("foo".getBytes()), ByteBuffer.wrap((byte[]) converted));
+
+        Assert.assertEquals(ByteBuffer.wrap("foo".getBytes()),
+                AvroData.convertToAvro(ByteBuffer.wrap("foo".getBytes())));
+    }
+
+    @Test
+    public void testString() {
+        Assert.assertEquals("string", AvroData.convertToAvro("string"));
+    }
+
+    @Test
+    public void testComplex() {
+        Schema schema = SchemaBuilder.record("record").fields()
+                .name("null").type().nullType().noDefault()
+                .requiredBoolean("boolean")
+                .requiredInt("int")
+                .requiredLong("long")
+                .requiredFloat("float")
+                .requiredDouble("double")
+                .requiredBytes("bytes")
+                .requiredString("string")
+                .name("union").type().unionOf().nullType().and().intType().endUnion().noDefault()
+                .name("array").type().array().items().intType().noDefault()
+                .name("map").type().map().values().intType().noDefault()
+                .name("fixed").type().fixed("fixed").size(3).noDefault()
+                .name("enum").type().enumeration("enum").symbols("one", "two").noDefault()
+                .endRecord();
+        GenericRecord record = new GenericRecordBuilder(schema)
+                .set("null", null)
+                .set("boolean", true)
+                .set("int", 12)
+                .set("long", 12L)
+                .set("float", 12.2f)
+                .set("double", 12.2)
+                .set("bytes", ByteBuffer.wrap("foo".getBytes()))
+                .set("string", "string-value")
+                .set("union", 12)
+                .set("array", Arrays.asList(1, 2, 3))
+                .set("map", Collections.singletonMap("field", 1))
+                .set("fixed", ByteBuffer.wrap("foo".getBytes()))
+                .set("enum", "one")
+                .build();
+
+        Object convertedRecord = AvroData.convertToAvro(record);
+
+        org.apache.avro.Schema avroSchema = org.apache.avro.SchemaBuilder.record("record").fields()
+                .name("null").type().nullType().noDefault()
+                .requiredBoolean("boolean")
+                .requiredInt("int")
+                .requiredLong("long")
+                .requiredFloat("float")
+                .requiredDouble("double")
+                .requiredBytes("bytes")
+                .requiredString("string")
+                .name("union").type().unionOf().nullType().and().intType().endUnion().noDefault()
+                .name("array").type().array().items().intType().noDefault()
+                .name("map").type().map().values().intType().noDefault()
+                .name("fixed").type().fixed("fixed").size(3).noDefault()
+                .name("enum").type().enumeration("enum").symbols("one", "two").noDefault()
+                .endRecord();
+        org.apache.avro.generic.GenericRecord avroRecord
+                = new org.apache.avro.generic.GenericRecordBuilder(avroSchema)
+                .set("null", null)
+                .set("boolean", true)
+                .set("int", 12)
+                .set("long", 12L)
+                .set("float", 12.2f)
+                .set("double", 12.2)
+                .set("bytes", ByteBuffer.wrap("foo".getBytes()))
+                .set("string", "string-value")
+                .set("union", 12)
+                .set("array", Arrays.asList(1, 2, 3))
+                .set("map", Collections.singletonMap("field", 1))
+                .set("fixed", ByteBuffer.wrap("foo".getBytes()))
+                .set("enum", "one")
+                .build();
+
+        assertEquals(avroSchema, ((org.apache.avro.generic.GenericRecord) convertedRecord).getSchema());
+        assertEquals(avroRecord, convertedRecord);
+    }
+
+}

copycat-avro/src/test/java/org/apache/kafka/copycat/avro/AvroDataToCopycatTest.java

@@ -0,0 +1,154 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.avro;
+
+import org.apache.kafka.copycat.data.GenericRecord;
+import org.apache.kafka.copycat.data.GenericRecordBuilder;
+import org.apache.kafka.copycat.data.Schema;
+import org.apache.kafka.copycat.data.SchemaBuilder;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.Collections;
+
+import static org.junit.Assert.*;
+
+// Tests AvroData's conversion of Avro -> Copycat
+public class AvroDataToCopycatTest {
+
+    // All the primitive types are pass-through
+
+    @Test
+    public void testNull() {
+        assertNull(AvroData.convertFromAvro(null));
+    }
+
+    @Test
+    public void testBoolean() {
+        Assert.assertEquals(true, AvroData.convertFromAvro(true));
+    }
+
+    @Test
+    public void testInteger() {
+        Assert.assertEquals(12, AvroData.convertFromAvro(12));
+    }
+
+    @Test
+    public void testLong() {
+        Assert.assertEquals(12L, AvroData.convertFromAvro(12L));
+    }
+
+    @Test
+    public void testFloat() {
+        Assert.assertEquals(12.2f, AvroData.convertFromAvro(12.2f));
+    }
+
+    @Test
+    public void testDouble() {
+        Assert.assertEquals(12.2, AvroData.convertFromAvro(12.2));
+    }
+
+    @Test
+    public void testBytes() {
+        Object converted = AvroData.convertFromAvro("foo".getBytes());
+        assertTrue(converted instanceof byte[]);
+        assertEquals(ByteBuffer.wrap("foo".getBytes()), ByteBuffer.wrap((byte[]) converted));
+
+        Assert.assertEquals(ByteBuffer.wrap("foo".getBytes()),
+                AvroData.convertFromAvro(ByteBuffer.wrap("foo".getBytes())));
+    }
+
+    @Test
+    public void testString() {
+        Assert.assertEquals("string", AvroData.convertFromAvro("string"));
+    }
+
+    @Test
+    public void testComplex() {
+        org.apache.avro.Schema avroSchema = org.apache.avro.SchemaBuilder.record("record").fields()
+                .name("null").type().nullType().noDefault()
+                .requiredBoolean("boolean")
+                .requiredInt("int")
+                .requiredLong("long")
+                .requiredFloat("float")
+                .requiredDouble("double")
+                .requiredBytes("bytes")
+                .requiredString("string")
+                .name("union").type().unionOf().nullType().and().intType().endUnion().noDefault()
+                .name("array").type().array().items().intType().noDefault()
+                .name("map").type().map().values().intType().noDefault()
+                .name("fixed").type().fixed("fixed").size(3).noDefault()
+                .name("enum").type().enumeration("enum").symbols("one", "two").noDefault()
+                .endRecord();
+        org.apache.avro.generic.GenericRecord avroRecord
+                = new org.apache.avro.generic.GenericRecordBuilder(avroSchema)
+                .set("null", null)
+                .set("boolean", true)
+                .set("int", 12)
+                .set("long", 12L)
+                .set("float", 12.2f)
+                .set("double", 12.2)
+                .set("bytes", ByteBuffer.wrap("foo".getBytes()))
+                .set("string", "string-value")
+                .set("union", 12)
+                .set("array", Arrays.asList(1, 2, 3))
+                .set("map", Collections.singletonMap("field", 1))
+                .set("fixed", ByteBuffer.wrap("foo".getBytes()))
+                .set("enum", "one")
+                .build();
+
+        Object convertedRecord = AvroData.convertFromAvro(avroRecord);
+
+        Schema schema = SchemaBuilder.record("record").fields()
+                .name("null").type().nullType().noDefault()
+                .requiredBoolean("boolean")
+                .requiredInt("int")
+                .requiredLong("long")
+                .requiredFloat("float")
+                .requiredDouble("double")
+                .requiredBytes("bytes")
+                .requiredString("string")
+                .name("union").type().unionOf().nullType().and().intType().endUnion().noDefault()
+                .name("array").type().array().items().intType().noDefault()
+                .name("map").type().map().values().intType().noDefault()
+                .name("fixed").type().fixed("fixed").size(3).noDefault()
+                .name("enum").type().enumeration("enum").symbols("one", "two").noDefault()
+                .endRecord();
+        GenericRecord record = new GenericRecordBuilder(schema)
+                .set("null", null)
+                .set("boolean", true)
+                .set("int", 12)
+                .set("long", 12L)
+                .set("float", 12.2f)
+                .set("double", 12.2)
+                .set("bytes", ByteBuffer.wrap("foo".getBytes()))
+                .set("string", "string-value")
+                .set("union", 12)
+                .set("array", Arrays.asList(1, 2, 3))
+                .set("map", Collections.singletonMap("field", 1))
+                .set("fixed", ByteBuffer.wrap("foo".getBytes()))
+                .set("enum", "one")
+                .build();
+
+        assertEquals(schema, ((GenericRecord) convertedRecord).getSchema());
+        assertEquals(record, convertedRecord);
+    }
+
+}

copycat-avro/src/test/java/org/apache/kafka/copycat/avro/AvroOffsetStorageReaderTest.java

@@ -0,0 +1,229 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.avro;
+/*
+import org.apache.kafka.copycat.data.Schema;
+import org.apache.kafka.copycat.data.SchemaBuilder;
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.easymock.Capture;
+import org.easymock.EasyMock;
+import org.junit.Before;
+import org.junit.Test;
+import org.powermock.api.easymock.PowerMock;
+
+import java.nio.ByteBuffer;
+import java.util.*;
+import java.util.concurrent.Future;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+*/
+public class AvroOffsetStorageReaderTest {
+
+    /* FIXME
+    private static final String namespace = "namespace";
+    private OffsetBackingStore offsetBackingStore;
+    private OffsetStorageReaderImpl offsetReader;
+
+    // Most requests will make a request to the underlying storage and want to verify some info
+    // about that request
+    private Capture<Collection<ByteBuffer>> requestKeys;
+    private Capture<Callback<Map<ByteBuffer, ByteBuffer>>> callback;
+    private Future<Map<ByteBuffer, ByteBuffer>> storeFuture;
+
+
+    // Cover a few different types to verify serialization works and that for keys we're allowed to
+    // mix-and-match within a single request
+    // TODO Add testing of complex types for stream IDs & offsets to these primitive types
+    private static final List<Object> streamIds = Arrays.asList((Object) "stream1", (Object) 52);
+    private static final Object nullStreamId = null;
+    // Same as streamIds but with extra, unserializable entry
+    private static final List<Object> streamIdsWithUnserializable
+            = Arrays.asList((Object) "stream1", (Object) 52, new Date());
+    private static final List<Object> longOffsets = Arrays.asList((Object) 12L, (Object) 24L);
+    private static final List<Object> stringOffsets = Arrays.asList(
+            (Object) "offset1", (Object) "offset2");
+    private static final Schema longSchema = SchemaBuilder.builder().longType();
+    private static final Schema stringSchema = SchemaBuilder.builder().stringType();
+    // Serialized form of data to be returned by the storage layer
+    private static final Map<ByteBuffer, ByteBuffer> longsSerialized
+            = new HashMap<ByteBuffer, ByteBuffer>();
+    private static final Map<ByteBuffer, ByteBuffer> stringsSerialized
+            = new HashMap<ByteBuffer, ByteBuffer>();
+    private static final Map<ByteBuffer, ByteBuffer> singleLongSerialized
+            = new HashMap<ByteBuffer, ByteBuffer>();
+    private static final Map<ByteBuffer, ByteBuffer> nullsSerialized
+            = new HashMap<ByteBuffer, ByteBuffer>();
+    private static final Map<ByteBuffer, ByteBuffer> longsSerializedWithInvalid
+            = new HashMap<ByteBuffer, ByteBuffer>();
+
+    static {
+        for (int i = 0; i < longOffsets.size(); i++) {
+            longsSerialized.put(
+                    AvroData.serializeToAvro(streamIds.get(i)),
+                    AvroData.serializeToAvro(longOffsets.get(i)));
+        }
+
+        for (int i = 0; i < stringOffsets.size(); i++) {
+            stringsSerialized.put(
+                    AvroData.serializeToAvro(streamIds.get(i)),
+                    AvroData.serializeToAvro(stringOffsets.get(i)));
+        }
+
+        singleLongSerialized.put(
+                AvroData.serializeToAvro(streamIds.get(0)),
+                AvroData.serializeToAvro(longOffsets.get(0)));
+
+        nullsSerialized.put(null, null);
+
+        longsSerializedWithInvalid.put(
+                AvroData.serializeToAvro(streamIds.get(0)),
+                AvroData.serializeToAvro(longOffsets.get(0)));
+        // You need to be careful about the bytes specified here because Avro's variable length
+        // encoding allows some short byte sequences to be valid values for a long
+        longsSerializedWithInvalid.put(
+                AvroData.serializeToAvro(streamIds.get(1)),
+                ByteBuffer.wrap(new byte[0]));
+
+    }
+
+
+    @Before
+    public void setup() {
+        offsetBackingStore = PowerMock.createMock(OffsetBackingStore.class);
+        offsetReader = new OffsetStorageReaderImpl(offsetBackingStore, namespace);
+
+        requestKeys = EasyMock.newCapture();
+        callback = EasyMock.newCapture();
+        storeFuture = PowerMock.createMock(Future.class);
+    }
+
+    @Test
+    public void testGetOffsetsStringValues() throws Exception {
+        expectStoreRequest(stringsSerialized);
+
+        PowerMock.replayAll();
+
+        Map<Object, Object> result = offsetReader.getOffsets(streamIds, stringSchema);
+        assertEquals(2, requestKeys.getValue().size());
+        assertEquals(mapFromLists(streamIds, stringOffsets), result);
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testGetOffsetsLongValues() throws Exception {
+        expectStoreRequest(longsSerialized);
+
+        PowerMock.replayAll();
+
+        Map<Object, Object> result = offsetReader.getOffsets(streamIds, longSchema);
+        assertEquals(2, requestKeys.getValue().size());
+        assertEquals(mapFromLists(streamIds, longOffsets), result);
+
+        PowerMock.verifyAll();
+    }
+
+    // getOffset() isn't too interesting since it's just a degenerate form of getOffsets(), so we
+    // just do one simple validation
+    @Test
+    public void testGetOffset() throws Exception {
+        expectStoreRequest(singleLongSerialized);
+
+        PowerMock.replayAll();
+
+        Object result = offsetReader.getOffset(streamIds.get(0), longSchema);
+        assertEquals(1, requestKeys.getValue().size());
+        assertEquals(longOffsets.get(0), result);
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testGetOffsetsNulls() throws Exception {
+        // Should be able to store/load null values
+        expectStoreRequest(nullsSerialized);
+
+        PowerMock.replayAll();
+
+        Object result = offsetReader.getOffset(null, longSchema);
+        assertEquals(1, requestKeys.getValue().size());
+        assertNull(result);
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testSerializationErrorReturnsOtherResults() throws Exception {
+        expectStoreRequest(longsSerialized);
+
+        PowerMock.replayAll();
+
+        Map<Object, Object> result = offsetReader.getOffsets(streamIdsWithUnserializable, longSchema);
+        assertEquals(2, requestKeys.getValue().size());
+        assertEquals(mapFromLists(streamIds, longOffsets), result);
+
+        PowerMock.verifyAll();
+    }
+
+    @Test(expected = CopycatRuntimeException.class)
+    public void testStorageGetFailed() throws Exception {
+        // backing store failed -> CopycatRuntimeException
+        EasyMock.expect(offsetBackingStore.get(EasyMock.eq(namespace), EasyMock.capture(requestKeys),
+                EasyMock.capture(callback)))
+                .andReturn(storeFuture);
+        EasyMock.expect(storeFuture.get())
+                .andThrow(new RuntimeException("failed to get data from backing store"));
+
+        PowerMock.replayAll();
+
+        Map<Object, Object> result = offsetReader.getOffsets(streamIds, longSchema);
+        assertEquals(2, requestKeys.getValue().size()); // throws
+    }
+
+    @Test
+    public void testUndeserializeableData() throws Exception {
+        // Should return whatever data it can, ignoring the unserializeable data
+        expectStoreRequest(longsSerializedWithInvalid);
+
+        PowerMock.replayAll();
+
+        Map<Object, Object> result = offsetReader.getOffsets(streamIds, longSchema);
+        assertEquals(2, requestKeys.getValue().size());
+        assertEquals(mapFromLists(streamIds.subList(0, 1), longOffsets.subList(0, 1)), result);
+
+        PowerMock.verifyAll();
+    }
+
+
+    private void expectStoreRequest(Map<ByteBuffer, ByteBuffer> result) throws Exception {
+        EasyMock.expect(offsetBackingStore.get(EasyMock.eq(namespace), EasyMock.capture(requestKeys),
+                EasyMock.capture(callback)))
+                .andReturn(storeFuture);
+        EasyMock.expect(storeFuture.get()).andReturn(result);
+    }
+
+    private Map<Object, Object> mapFromLists(List<Object> keys, List<Object> values) {
+        Map<Object, Object> result = new HashMap<Object, Object>();
+        for (int i = 0; i < keys.size(); i++) {
+            result.put(keys.get(i), values.get(i));
+        }
+        return result;
+    }
+    */
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/cli/CopycatCommand.java

@@ -0,0 +1,110 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.cli;
+
+import org.apache.kafka.common.config.ConfigException;
+import org.apache.kafka.common.utils.Utils;
+import org.apache.kafka.copycat.runtime.Coordinator;
+import org.apache.kafka.copycat.runtime.Copycat;
+import org.apache.kafka.copycat.runtime.Worker;
+import org.apache.kafka.copycat.runtime.standalone.StandaloneCoordinator;
+import org.apache.kafka.copycat.util.Callback;
+import org.apache.kafka.copycat.util.FutureCallback;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Properties;
+
+/**
+ * <p>
+ * Command line utility that runs Copycat as a standalone process. In this mode, work is not
+ * distributed. Instead, all the normal Copycat machinery works within a single process. This is
+ * useful for ad hoc, small, or experimental jobs.
+ * </p>
+ * <p>
+ * By default, no job configs or offset data is persistent. You can make jobs persistent and
+ * fault tolerant by overriding the settings to use file storage for both.
+ * </p>
+ */
+public class CopycatCommand {
+    private static final Logger log = LoggerFactory.getLogger(CopycatCommand.class);
+
+    public static void main(String[] args) throws Exception {
+        CopycatCommandConfig config;
+        Properties workerProps;
+        Properties connectorProps;
+
+        try {
+            config = CopycatCommandConfig.parseCommandLineArgs(args);
+        } catch (ConfigException e) {
+            log.error(e.getMessage());
+            log.info("Usage: copycat [--worker-config worker.properties]"
+                    + " [--create-connectors connector1.properties,connector2.properties,...]"
+                    + " [--delete-connectors connector1-name,connector2-name,...]");
+            System.exit(1);
+            return;
+        }
+
+        String workerPropsFile = config.getString(CopycatCommandConfig.WORKER_PROPERTIES_CONFIG);
+        workerProps = !workerPropsFile.isEmpty() ? Utils.loadProps(workerPropsFile) : new Properties();
+
+        WorkerConfig workerConfig = new WorkerConfig(workerProps);
+        Worker worker = new Worker(workerConfig);
+        Coordinator coordinator = new StandaloneCoordinator(worker, workerConfig.getUnusedProperties());
+        final Copycat copycat = new Copycat(worker, coordinator);
+        copycat.start();
+
+        try {
+            // Destroy any requested connectors
+            for (final String connName : config.getList(CopycatCommandConfig.DELETE_CONNECTORS_CONFIG)) {
+                FutureCallback cb = new FutureCallback(new Callback<Void>() {
+                    @Override
+                    public void onCompletion(Throwable error, Void result) {
+                        if (error != null) {
+                            log.error("Failed to stop job {}", connName);
+                        }
+                    }
+                });
+                coordinator.deleteConnector(connName, cb);
+                cb.get();
+            }
+
+            // Create any new connectors
+            for (final String connectorPropsFile : config
+                    .getList(CopycatCommandConfig.CREATE_CONNECTORS_CONFIG)) {
+                connectorProps = Utils.loadProps(connectorPropsFile);
+                FutureCallback cb = new FutureCallback(new Callback<String>() {
+                    @Override
+                    public void onCompletion(Throwable error, String id) {
+                        if (error != null) {
+                            log.error("Failed to create job for {}", connectorPropsFile);
+                        }
+                    }
+                });
+                coordinator.addConnector(connectorProps, cb);
+                cb.get();
+            }
+        } catch (Throwable t) {
+            log.error("Stopping after connector error", t);
+            copycat.stop();
+        }
+
+        // Shutdown will be triggered by Ctrl-C or via HTTP shutdown request
+        copycat.awaitStop();
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/cli/CopycatCommandConfig.java

@@ -0,0 +1,96 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.cli;
+
+import org.apache.kafka.common.config.AbstractConfig;
+import org.apache.kafka.common.config.ConfigDef;
+import org.apache.kafka.common.config.ConfigDef.Importance;
+import org.apache.kafka.common.config.ConfigDef.Type;
+
+import java.util.Properties;
+
+public class CopycatCommandConfig extends AbstractConfig {
+
+    public static final String WORKER_PROPERTIES_CONFIG = "worker-config";
+    public static final String WORKER_PROPERTIES_CONFIG_DEFAULT = "";
+    private static final String WORKER_PROPERTIES_CONFIG_DOC =
+            "Path to a properties file with worker configuration.";
+
+    public static final String CREATE_CONNECTORS_CONFIG = "create-connectors";
+    public static final String CREATE_CONNECTORS_CONFIG_DEFAULT = "";
+    private static final String CREATE_CONNECTORS_CONFIG_DOC =
+            "List of paths to properties files with connector properties to use to create new connectors";
+
+    public static final String DELETE_CONNECTORS_CONFIG = "delete-connectors";
+    public static final String DELETE_CONNECTORS_CONFIG_DEFAULT = "";
+    private static final String DELETE_CONNECTORS_CONFIG_DOC = "List of names of a connectors to "
+            + "stop and delete.";
+
+    private static ConfigDef config;
+
+    static {
+        config = new ConfigDef()
+                .define(WORKER_PROPERTIES_CONFIG, Type.STRING, WORKER_PROPERTIES_CONFIG_DEFAULT,
+                        Importance.HIGH, WORKER_PROPERTIES_CONFIG_DOC)
+                .define(CREATE_CONNECTORS_CONFIG, Type.LIST, CREATE_CONNECTORS_CONFIG_DEFAULT,
+                        Importance.HIGH, CREATE_CONNECTORS_CONFIG_DOC)
+                .define(DELETE_CONNECTORS_CONFIG, Type.LIST, DELETE_CONNECTORS_CONFIG_DEFAULT,
+                        Importance.HIGH, DELETE_CONNECTORS_CONFIG_DOC);
+    }
+
+    private Properties originalProperties;
+
+    public CopycatCommandConfig(Properties props) {
+        super(config, props);
+        this.originalProperties = props;
+    }
+
+    /**
+     * Parses command line arguments into a Properties object and instantiate a
+     * CopycatCommandConfig with it.
+     * @param args
+     * @return
+     */
+    public static CopycatCommandConfig parseCommandLineArgs(String[] args) {
+        Properties props = new Properties();
+        for (int i = 0; i < args.length; i++) {
+            String arg = args[i];
+            String key, value;
+
+            // Check for foo=bar or --foo=bar syntax
+            if (arg.contains("=")) {
+                String[] parts = arg.split("=", 1);
+                key = parts[0];
+                value = parts[1];
+            } else {
+                key = args[i];
+                i += 1;
+                value = args[i];
+            }
+
+            // Check for -- prefix on key
+            if (key.startsWith("--")) {
+                key = key.substring(2);
+            }
+
+            props.setProperty(key, value);
+        }
+
+        return new CopycatCommandConfig(props);
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/cli/WorkerConfig.java

@@ -0,0 +1,227 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.cli;
+
+import org.apache.kafka.common.config.AbstractConfig;
+import org.apache.kafka.common.config.ConfigDef;
+import org.apache.kafka.common.config.ConfigDef.Importance;
+import org.apache.kafka.common.config.ConfigDef.Type;
+
+import java.util.Properties;
+import java.util.Set;
+
+/**
+ * Configuration for standalone workers.
+ */
+public class WorkerConfig extends AbstractConfig {
+
+    public static final String CLUSTER_CONFIG = "cluster";
+    private static final String
+            CLUSTER_CONFIG_DOC =
+            "ID for this cluster, which is used to provide a namespace so multiple Copycat clusters "
+                    + "or instances may co-exist while sharing a single Kafka cluster.";
+    public static final String CLUSTER_DEFAULT = "copycat";
+
+    public static final String ZOOKEEPER_CONNECT_CONFIG = "zookeeper.connect";
+    private static final String ZOOKEEPER_CONNECT_DOC =
+            "Specifies the ZooKeeper connection string in the form "
+                    + "hostname:port where host and port are the host and port of a ZooKeeper server. To allow connecting "
+                    + "through other ZooKeeper nodes when that ZooKeeper machine is down you can also specify multiple hosts "
+                    + "in the form hostname1:port1,hostname2:port2,hostname3:port3.\n"
+                    + "\n"
+                    + "The server may also have a ZooKeeper chroot path as part of it's ZooKeeper connection string which puts "
+                    + "its data under some path in the global ZooKeeper namespace. If so the consumer should use the same "
+                    + "chroot path in its connection string. For example to give a chroot path of /chroot/path you would give "
+                    + "the connection string as hostname1:port1,hostname2:port2,hostname3:port3/chroot/path.";
+    public static final String ZOOKEEPER_CONNECT_DEFAULT = "localhost:2181";
+
+    public static final String ZOOKEEPER_SESSION_TIMEOUT_MS_CONFIG = "zookeeper.session.timeout.ms";
+    private static final String ZOOKEEPER_SESSION_TIMEOUT_MS_DOC
+            = "Session timeout for ZooKeeper connections.";
+    public static final String ZOOKEEPER_SESSION_TIMEOUT_MS_DEFAULT = "30000";
+
+    public static final String ZOOKEEPER_CONNECTION_TIMEOUT_MS_CONFIG
+            = "zookeeper.session.connection.ms";
+    private static final String ZOOKEEPER_CONNECTION_TIMEOUT_MS_DOC
+            = "Connection timeout for ZooKeeper.";
+    public static final String ZOOKEEPER_CONNECTION_TIMEOUT_MS_DEFAULT = "30000";
+
+    public static final String BOOTSTRAP_SERVERS_CONFIG = "bootstrap.servers";
+    public static final String BOOSTRAP_SERVERS_DOC
+            = "A list of host/port pairs to use for establishing the initial connection to the Kafka "
+            + "cluster. The client will make use of all servers irrespective of which servers are "
+            + "specified here for bootstrapping&mdash;this list only impacts the initial hosts used "
+            + "to discover the full set of servers. This list should be in the form "
+            + "<code>host1:port1,host2:port2,...</code>. Since these servers are just used for the "
+            + "initial connection to discover the full cluster membership (which may change "
+            + "dynamically), this list need not contain the full set of servers (you may want more "
+            + "than one, though, in case a server is down).";
+    public static final String BOOTSTRAP_SERVERS_DEFAULT = "localhost:9092";
+
+    public static final String CONVERTER_CLASS_CONFIG = "converter";
+    public static final String CONVERTER_CLASS_DOC =
+            "Converter class for Copycat data that implements the <code>Converter</code> interface.";
+    public static final String CONVERTER_CLASS_DEFAULT
+            = "org.apache.kafka.copycat.avro.AvroConverter"; // TODO: Non-avro built-in?
+
+    public static final String KEY_SERIALIZER_CLASS_CONFIG = "key.serializer";
+    public static final String KEY_SERIALIZER_CLASS_DOC =
+            "Serializer class for key that implements the <code>Serializer</code> interface.";
+    public static final String KEY_SERIALIZER_CLASS_DEFAULT
+            = "io.confluent.kafka.serializers.KafkaAvroSerializer"; // TODO: Non-avro built-in?
+
+    public static final String VALUE_SERIALIZER_CLASS_CONFIG = "value.serializer";
+    public static final String VALUE_SERIALIZER_CLASS_DOC =
+            "Serializer class for value that implements the <code>Serializer</code> interface.";
+    public static final String VALUE_SERIALIZER_CLASS_DEFAULT
+            = "io.confluent.kafka.serializers.KafkaAvroSerializer"; // TODO: Non-avro built-in?
+
+    public static final String OFFSET_KEY_SERIALIZER_CLASS_CONFIG = "offset.key.serializer";
+    public static final String OFFSET_KEY_SERIALIZER_CLASS_DOC =
+            "Serializer class for key that implements the <code>OffsetSerializer</code> interface.";
+    public static final String OFFSET_KEY_SERIALIZER_CLASS_DEFAULT
+            = "org.apache.kafka.copycat.avro.AvroSerializer"; // TODO: Non-avro built-in?
+
+    public static final String OFFSET_VALUE_SERIALIZER_CLASS_CONFIG = "offset.value.serializer";
+    public static final String OFFSET_VALUE_SERIALIZER_CLASS_DOC =
+            "Serializer class for value that implements the <code>OffsetSerializer</code> interface.";
+    public static final String OFFSET_VALUE_SERIALIZER_CLASS_DEFAULT
+            = "org.apache.kafka.copycat.avro.AvroSerializer"; // TODO: Non-avro built-in?
+
+
+    public static final String KEY_DESERIALIZER_CLASS_CONFIG = "key.deserializer";
+    public static final String KEY_DESERIALIZER_CLASS_DOC =
+            "Serializer class for key that implements the <code>Deserializer</code> interface.";
+    public static final String KEY_DESERIALIZER_CLASS_DEFAULT
+            = "io.confluent.kafka.serializers.KafkaAvroDeserializer"; // TODO: Non-avro built-in?
+
+    public static final String VALUE_DESERIALIZER_CLASS_CONFIG = "value.deserializer";
+    public static final String VALUE_DESERIALIZER_CLASS_DOC =
+            "Deserializer class for value that implements the <code>Deserializer</code> interface.";
+    public static final String VALUE_DESERIALIZER_CLASS_DEFAULT
+            = "io.confluent.kafka.serializers.KafkaAvroDeserializer"; // TODO: Non-avro built-in?
+
+    public static final String OFFSET_KEY_DESERIALIZER_CLASS_CONFIG = "offset.key.deserializer";
+    public static final String OFFSET_KEY_DESERIALIZER_CLASS_DOC =
+            "Deserializer class for key that implements the <code>OffsetDeserializer</code> interface.";
+    public static final String OFFSET_KEY_DESERIALIZER_CLASS_DEFAULT
+            = "org.apache.kafka.copycat.avro.AvroDeserializer"; // TODO: Non-avro built-in?
+
+    public static final String OFFSET_VALUE_DESERIALIZER_CLASS_CONFIG = "offset.value.deserializer";
+    public static final String OFFSET_VALUE_DESERIALIZER_CLASS_DOC =
+            "Deserializer class for value that implements the <code>OffsetDeserializer</code> interface.";
+    public static final String OFFSET_VALUE_DESERIALIZER_CLASS_DEFAULT
+            = "org.apache.kafka.copycat.avro.AvroDeserializer"; // TODO: Non-avro built-in?
+
+
+    public static final String TASK_SHUTDOWN_GRACEFUL_TIMEOUT_MS_CONFIG
+            = "task.shutdown.graceful.timeout.ms";
+    private static final String TASK_SHUTDOWN_GRACEFUL_TIMEOUT_MS_DOC =
+            "Amount of time to wait for tasks to shutdown gracefully. This is the total amount of time,"
+                    + " not per task. All task have shutdown triggered, then they are waited on sequentially.";
+    private static final String TASK_SHUTDOWN_GRACEFUL_TIMEOUT_MS_DEFAULT = "5000";
+
+    public static final String OFFSET_STORAGE_CLASS_CONFIG = "offset.storage.class";
+    private static final String OFFSET_STORAGE_CLASS_DOC =
+            "OffsetBackingStore implementation to use for storing stream offset data";
+    public static final String OFFSET_STORAGE_CLASS_DEFAULT
+            = "org.apache.kafka.copycat.storage.MemoryOffsetBackingStore";
+
+    public static final String OFFSET_COMMIT_INTERVAL_MS_CONFIG = "offset.flush.interval.ms";
+    private static final String OFFSET_COMMIT_INTERVAL_MS_DOC
+            = "Interval at which to try committing offsets for tasks.";
+    public static final long OFFSET_COMMIT_INTERVAL_MS_DEFAULT = 60000L;
+
+    public static final String OFFSET_COMMIT_TIMEOUT_MS_CONFIG = "offset.flush.timeout.ms";
+    private static final String OFFSET_COMMIT_TIMEOUT_MS_DOC
+            = "Maximum number of milliseconds to wait for records to flush and stream offset data to be"
+            + " committed to offset storage before cancelling the process and restoring the offset "
+            + "data to be committed in a future attempt.";
+    public static final long OFFSET_COMMIT_TIMEOUT_MS_DEFAULT = 5000L;
+
+    private static ConfigDef config;
+
+    static {
+        config = new ConfigDef()
+                .define(CLUSTER_CONFIG, Type.STRING, CLUSTER_DEFAULT, Importance.HIGH, CLUSTER_CONFIG_DOC)
+                .define(ZOOKEEPER_CONNECT_CONFIG, Type.STRING, ZOOKEEPER_CONNECT_DEFAULT,
+                        Importance.HIGH, ZOOKEEPER_CONNECT_DOC)
+                .define(ZOOKEEPER_SESSION_TIMEOUT_MS_CONFIG, Type.INT,
+                        ZOOKEEPER_SESSION_TIMEOUT_MS_DEFAULT,
+                        Importance.LOW, ZOOKEEPER_SESSION_TIMEOUT_MS_DOC)
+                .define(ZOOKEEPER_CONNECTION_TIMEOUT_MS_CONFIG, Type.INT,
+                        ZOOKEEPER_CONNECTION_TIMEOUT_MS_DEFAULT,
+                        Importance.LOW, ZOOKEEPER_CONNECTION_TIMEOUT_MS_DOC)
+                .define(BOOTSTRAP_SERVERS_CONFIG, Type.LIST, BOOTSTRAP_SERVERS_DEFAULT,
+                        Importance.HIGH, BOOSTRAP_SERVERS_DOC)
+                .define(CONVERTER_CLASS_CONFIG, Type.CLASS, CONVERTER_CLASS_DEFAULT,
+                        Importance.HIGH, CONVERTER_CLASS_DOC)
+                .define(KEY_SERIALIZER_CLASS_CONFIG, Type.CLASS, KEY_SERIALIZER_CLASS_DEFAULT,
+                        Importance.HIGH, KEY_SERIALIZER_CLASS_DOC)
+                .define(VALUE_SERIALIZER_CLASS_CONFIG, Type.CLASS, VALUE_SERIALIZER_CLASS_DEFAULT,
+                        Importance.HIGH, VALUE_SERIALIZER_CLASS_DOC)
+                .define(OFFSET_KEY_SERIALIZER_CLASS_CONFIG, Type.CLASS, OFFSET_KEY_SERIALIZER_CLASS_DEFAULT,
+                        Importance.HIGH, OFFSET_KEY_SERIALIZER_CLASS_DOC)
+                .define(OFFSET_VALUE_SERIALIZER_CLASS_CONFIG, Type.CLASS,
+                        OFFSET_VALUE_SERIALIZER_CLASS_DEFAULT,
+                        Importance.HIGH, OFFSET_VALUE_SERIALIZER_CLASS_DOC)
+                .define(KEY_DESERIALIZER_CLASS_CONFIG, Type.CLASS, KEY_DESERIALIZER_CLASS_DEFAULT,
+                        Importance.HIGH, KEY_DESERIALIZER_CLASS_DOC)
+                .define(VALUE_DESERIALIZER_CLASS_CONFIG, Type.CLASS, VALUE_DESERIALIZER_CLASS_DEFAULT,
+                        Importance.HIGH, VALUE_DESERIALIZER_CLASS_DOC)
+                .define(OFFSET_KEY_DESERIALIZER_CLASS_CONFIG, Type.CLASS,
+                        OFFSET_KEY_DESERIALIZER_CLASS_DEFAULT,
+                        Importance.HIGH, OFFSET_KEY_DESERIALIZER_CLASS_DOC)
+                .define(OFFSET_VALUE_DESERIALIZER_CLASS_CONFIG, Type.CLASS,
+                        OFFSET_VALUE_DESERIALIZER_CLASS_DEFAULT,
+                        Importance.HIGH, OFFSET_VALUE_DESERIALIZER_CLASS_DOC)
+                .define(TASK_SHUTDOWN_GRACEFUL_TIMEOUT_MS_CONFIG, Type.LONG,
+                        TASK_SHUTDOWN_GRACEFUL_TIMEOUT_MS_DEFAULT, Importance.LOW,
+                        TASK_SHUTDOWN_GRACEFUL_TIMEOUT_MS_DOC)
+                .define(OFFSET_STORAGE_CLASS_CONFIG, Type.CLASS, OFFSET_STORAGE_CLASS_DEFAULT,
+                        Importance.LOW, OFFSET_STORAGE_CLASS_DOC)
+                .define(OFFSET_COMMIT_INTERVAL_MS_CONFIG, Type.LONG, OFFSET_COMMIT_INTERVAL_MS_DEFAULT,
+                        Importance.LOW, OFFSET_COMMIT_INTERVAL_MS_DOC)
+                .define(OFFSET_COMMIT_TIMEOUT_MS_CONFIG, Type.LONG, OFFSET_COMMIT_TIMEOUT_MS_DEFAULT,
+                        Importance.LOW, OFFSET_COMMIT_TIMEOUT_MS_DOC);
+    }
+
+    private Properties originalProperties;
+
+    public WorkerConfig() {
+        this(new Properties());
+    }
+
+    public WorkerConfig(Properties props) {
+        super(config, props);
+        this.originalProperties = props;
+    }
+
+    public Properties getUnusedProperties() {
+        Set<String> unusedKeys = this.unused();
+        Properties unusedProps = new Properties();
+        for (String key : unusedKeys) {
+            unusedProps.setProperty(key, originalProperties.getProperty(key));
+        }
+        return unusedProps;
+    }
+
+    public Properties getOriginalProperties() {
+        return originalProperties;
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/ConnectorConfig.java

@@ -0,0 +1,87 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.common.config.AbstractConfig;
+import org.apache.kafka.common.config.ConfigDef;
+import org.apache.kafka.common.config.ConfigDef.Importance;
+import org.apache.kafka.common.config.ConfigDef.Type;
+
+import java.util.Properties;
+import java.util.Set;
+
+/**
+ * <p>
+ * Configuration options for Connectors. These only include Copycat system-level configuration
+ * options (e.g. Connector class name, timeouts used by Copycat to control the connector) but does
+ * not include Connector-specific options (e.g. database connection settings).
+ * </p>
+ * <p>
+ * Note that some of these options are not required for all connectors. For example TOPICS_CONFIG
+ * is sink-specific.
+ * </p>
+ */
+public class ConnectorConfig extends AbstractConfig {
+
+    public static final String NAME_CONFIG = "name";
+    private static final String NAME_DOC = "Globally unique name to use for this connector.";
+
+    public static final String CONNECTOR_CLASS_CONFIG = "connector.class";
+    private static final String CONNECTOR_CLASS_DOC =
+            "Name of the class for this connector. Must be a subclass of org.apache.kafka.copycat.connector"
+                    + ".Connector";
+
+    public static final String TASKS_MAX_CONFIG = "tasks.max";
+    private static final String TASKS_MAX_DOC = "Maximum number of tasks to use for this connector.";
+    public static final int TASKS_MAX_DEFAULT = 1;
+
+    public static final String TOPICS_CONFIG = "topics";
+    private static final String TOPICS_DOC = "";
+    public static final String TOPICS_DEFAULT = "";
+
+    private static ConfigDef config;
+
+    static {
+        config = new ConfigDef()
+                .define(NAME_CONFIG, Type.STRING, Importance.HIGH, NAME_DOC)
+                .define(CONNECTOR_CLASS_CONFIG, Type.STRING, Importance.HIGH, CONNECTOR_CLASS_DOC)
+                .define(TASKS_MAX_CONFIG, Type.INT, TASKS_MAX_DEFAULT, Importance.HIGH, TASKS_MAX_DOC)
+                .define(TOPICS_CONFIG, Type.LIST, TOPICS_DEFAULT, Importance.HIGH, TOPICS_DOC);
+    }
+
+    private Properties originalProperties;
+
+    public ConnectorConfig() {
+        this(new Properties());
+    }
+
+    public ConnectorConfig(Properties props) {
+        super(config, props);
+        this.originalProperties = props;
+    }
+
+    public Properties getUnusedProperties() {
+        Set<String> unusedKeys = this.unused();
+        Properties unusedProps = new Properties();
+        for (String key : unusedKeys) {
+            unusedProps.setProperty(key, originalProperties.getProperty(key));
+        }
+        return unusedProps;
+    }
+
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/Coordinator.java

@@ -0,0 +1,52 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.copycat.util.Callback;
+
+import java.util.Properties;
+
+/**
+ * The Coordinator interface works with coordinators on other workers to manage a set of Jobs.
+ * Each job is a Connector instance with associated config and triggers tasks that are then run
+ * in workers. The assignment and tracking of those tasks in workers is also managed by the
+ * coordinator.
+ */
+public interface Coordinator {
+
+    void start();
+
+    void stop();
+
+    /**
+     * Submit a connector job to the cluster. This works from any node by forwarding the request to
+     * the leader coordinator if necessary.
+     *
+     * @param connectorProps user-specified properties for this job
+     * @param callback callback to invoke when the request completes
+     */
+    void addConnector(Properties connectorProps, Callback<String> callback);
+
+    /**
+     * Delete a connector job by name.
+     *
+     * @param name name of the connector job to shutdown and delete
+     * @param callback callback to invoke when the request completes
+     */
+    void deleteConnector(String name, Callback<Void> callback);
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/Copycat.java

@@ -0,0 +1,92 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * This class ties together all the components of a Copycat process (coordinator, worker,
+ * storage, command interface), managing their lifecycle.
+ */
+public class Copycat {
+    private static final Logger log = LoggerFactory.getLogger(Copycat.class);
+
+    private final Worker worker;
+    private final Coordinator coordinator;
+    private final CountDownLatch startLatch = new CountDownLatch(1);
+    private final CountDownLatch stopLatch = new CountDownLatch(1);
+    private final AtomicBoolean shutdown = new AtomicBoolean(false);
+    private final ShutdownHook shutdownHook;
+
+    public Copycat(Worker worker, Coordinator coordinator) {
+        log.debug("Copycat created");
+        this.worker = worker;
+        this.coordinator = coordinator;
+        shutdownHook = new ShutdownHook();
+    }
+
+    public void start() {
+        log.info("Copycat starting");
+        Runtime.getRuntime().addShutdownHook(shutdownHook);
+
+        worker.start();
+        coordinator.start();
+
+        log.info("Copycat started");
+
+        startLatch.countDown();
+    }
+
+    public void stop() {
+        boolean wasShuttingDown = shutdown.getAndSet(true);
+        if (!wasShuttingDown) {
+            log.info("Copycat stopping");
+
+            coordinator.stop();
+            worker.stop();
+
+            log.info("Copycat stopped");
+        }
+
+        stopLatch.countDown();
+    }
+
+    public void awaitStop() {
+        try {
+            stopLatch.await();
+        } catch (InterruptedException e) {
+            log.error("Interrupted waiting for Copycat to shutdown");
+        }
+    }
+
+    private class ShutdownHook extends Thread {
+        @Override
+        public void run() {
+            try {
+                startLatch.await();
+                Copycat.this.stop();
+            } catch (InterruptedException e) {
+                log.error("Interrupted in shutdown hook while waiting for copycat startup to finish");
+            }
+        }
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/SinkTaskContextImpl.java

@@ -0,0 +1,24 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.copycat.sink.SinkTaskContext;
+
+public class SinkTaskContextImpl extends SinkTaskContext {
+
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/SourceTaskOffsetCommitter.java

@@ -0,0 +1,104 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.common.utils.Time;
+import org.apache.kafka.copycat.cli.WorkerConfig;
+import org.apache.kafka.copycat.util.ConnectorTaskId;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.HashMap;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * <p>
+ * Manages offset commit scheduling and execution for SourceTasks.
+ * </p>
+ * <p>
+ * Unlike sink tasks which directly manage their offset commits in the main poll() thread since
+ * they drive the event loop and control (for all intents and purposes) the timeouts, source
+ * tasks are at the whim of the connector and cannot be guaranteed to wake up on the necessary
+ * schedule. Instead, this class tracks all the active tasks, their schedule for commits, and
+ * ensures they are invoked in a timely fashion.
+ * </p>
+ * <p>
+ *   The current implementation uses a single thread to process commits and
+ * </p>
+ */
+public class SourceTaskOffsetCommitter {
+    private static final Logger log = LoggerFactory.getLogger(SourceTaskOffsetCommitter.class);
+
+    private Time time;
+    private WorkerConfig config;
+    private ScheduledExecutorService commitExecutorService = null;
+    private HashMap<ConnectorTaskId, ScheduledFuture<?>> commiters
+            = new HashMap<ConnectorTaskId, ScheduledFuture<?>>();
+
+    SourceTaskOffsetCommitter(Time time, WorkerConfig config) {
+        this.time = time;
+        this.config = config;
+        commitExecutorService = Executors.newSingleThreadScheduledExecutor();
+    }
+
+    public void close(long timeoutMs) {
+        commitExecutorService.shutdown();
+        try {
+            if (!commitExecutorService.awaitTermination(timeoutMs, TimeUnit.MILLISECONDS)) {
+                log.error("Graceful shutdown of offset commitOffsets thread timed out.");
+            }
+        } catch (InterruptedException e) {
+            // ignore and allow to exit immediately
+        }
+    }
+
+    public void schedule(final ConnectorTaskId id, final WorkerSourceTask workerTask) {
+        long commitIntervalMs = config.getLong(WorkerConfig.OFFSET_COMMIT_INTERVAL_MS_CONFIG);
+        ScheduledFuture<?> commitFuture = commitExecutorService.scheduleWithFixedDelay(new Runnable() {
+            @Override
+            public void run() {
+                commit(workerTask);
+            }
+        }, commitIntervalMs, commitIntervalMs, TimeUnit.MILLISECONDS);
+        commiters.put(id, commitFuture);
+    }
+
+    public void remove(ConnectorTaskId id) {
+        ScheduledFuture<?> commitFuture = commiters.remove(id);
+        commitFuture.cancel(false);
+    }
+
+    public void commit(WorkerSourceTask workerTask) {
+        try {
+            log.debug("Committing offsets for {}", workerTask);
+            boolean success = workerTask.commitOffsets();
+            if (!success) {
+                log.error("Failed to commit offsets for {}", workerTask);
+            }
+        } catch (Throwable t) {
+            // We're very careful about exceptions here since any uncaught exceptions in the commit
+            // thread would cause the fixed interval schedule on the ExecutorService to stop running
+            // for that task
+            log.error("Unhandled exception when committing {}: ", workerTask, t);
+        }
+    }
+
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/Worker.java

@@ -0,0 +1,261 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.common.utils.SystemTime;
+import org.apache.kafka.common.utils.Time;
+import kafka.utils.ZKStringSerializer$;
+import org.I0Itec.zkclient.ZkClient;
+import org.apache.kafka.clients.producer.KafkaProducer;
+import org.apache.kafka.clients.producer.ProducerConfig;
+import org.apache.kafka.common.utils.Utils;
+import org.apache.kafka.copycat.cli.WorkerConfig;
+import org.apache.kafka.copycat.connector.Task;
+import org.apache.kafka.copycat.errors.CopycatException;
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.apache.kafka.copycat.sink.SinkTask;
+import org.apache.kafka.copycat.source.SourceTask;
+import org.apache.kafka.copycat.storage.*;
+import org.apache.kafka.copycat.util.ConnectorTaskId;
+import org.apache.kafka.copycat.util.Reflection;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+
+/**
+ * <p>
+ * Worker runs a (dynamic) set of tasks in a set of threads, doing the work of actually moving
+ * data to/from Kafka.
+ * </p>
+ * <p>
+ * Since each task has a dedicated thread, this is mainly just a container for them.
+ * </p>
+ */
+public class Worker {
+    private static final Logger log = LoggerFactory.getLogger(Worker.class);
+
+    private Time time;
+    private WorkerConfig config;
+    private Converter converter;
+    private OffsetBackingStore offsetBackingStore;
+    private OffsetSerializer offsetKeySerializer;
+    private OffsetSerializer offsetValueSerializer;
+    private OffsetDeserializer offsetKeyDeserializer;
+    private OffsetDeserializer offsetValueDeserializer;
+    private HashMap<ConnectorTaskId, WorkerTask> tasks = new HashMap<ConnectorTaskId, WorkerTask>();
+    private KafkaProducer producer;
+    private ZkClient zkClient;
+    private SourceTaskOffsetCommitter sourceTaskOffsetCommitter;
+
+    public Worker(WorkerConfig config) {
+        this(new SystemTime(), config,
+                Reflection.instantiateConfigurable(
+                        config.getClass(WorkerConfig.OFFSET_STORAGE_CLASS_CONFIG).getName(),
+                        OffsetBackingStore.class, config.getUnusedProperties()),
+                null, null, null, null,
+                createZkClient(config));
+    }
+
+    public Worker(Time time, WorkerConfig config, OffsetBackingStore offsetBackingStore,
+                  OffsetSerializer offsetKeySerializer, OffsetSerializer offsetValueSerializer,
+                  OffsetDeserializer offsetKeyDeserializer, OffsetDeserializer offsetValueDeserializer,
+                  ZkClient zkClient) {
+        this.time = time;
+        this.config = config;
+        this.converter = Reflection.instantiate(config.getClass(WorkerConfig.CONVERTER_CLASS_CONFIG).getName(),
+                Converter.class);
+        this.offsetBackingStore = offsetBackingStore;
+
+        if (offsetKeySerializer != null) {
+            this.offsetKeySerializer = offsetKeySerializer;
+        } else {
+            this.offsetKeySerializer = Reflection.instantiate(
+                    config.getClass(WorkerConfig.OFFSET_KEY_SERIALIZER_CLASS_CONFIG).getName(),
+                    OffsetSerializer.class);
+            this.offsetKeySerializer.configure(config.getOriginalProperties(), true);
+        }
+
+        if (offsetValueSerializer != null) {
+            this.offsetValueSerializer = offsetValueSerializer;
+        } else {
+            this.offsetValueSerializer = Reflection.instantiate(
+                    config.getClass(WorkerConfig.OFFSET_VALUE_SERIALIZER_CLASS_CONFIG).getName(),
+                    OffsetSerializer.class);
+            this.offsetValueSerializer.configure(config.getOriginalProperties(), false);
+        }
+
+        if (offsetKeyDeserializer != null) {
+            this.offsetKeyDeserializer = offsetKeyDeserializer;
+        } else {
+            this.offsetKeyDeserializer = Reflection.instantiate(
+                    config.getClass(WorkerConfig.OFFSET_KEY_DESERIALIZER_CLASS_CONFIG).getName(),
+                    OffsetDeserializer.class);
+            this.offsetKeyDeserializer.configure(config.getOriginalProperties(), true);
+        }
+
+        if (offsetValueDeserializer != null) {
+            this.offsetValueDeserializer = offsetValueDeserializer;
+        } else {
+            this.offsetValueDeserializer = Reflection.instantiate(
+                    config.getClass(WorkerConfig.OFFSET_VALUE_DESERIALIZER_CLASS_CONFIG).getName(),
+                    OffsetDeserializer.class);
+            this.offsetValueDeserializer.configure(config.getOriginalProperties(), false);
+        }
+
+        this.zkClient = zkClient;
+
+    }
+
+    private static ZkClient createZkClient(WorkerConfig config) {
+        return new ZkClient(config.getString(WorkerConfig.ZOOKEEPER_CONNECT_CONFIG),
+                config.getInt(WorkerConfig.ZOOKEEPER_SESSION_TIMEOUT_MS_CONFIG),
+                config.getInt(WorkerConfig.ZOOKEEPER_CONNECTION_TIMEOUT_MS_CONFIG),
+                ZKStringSerializer$.MODULE$);
+    }
+
+    public void start() {
+        log.info("Worker starting");
+
+        Properties unusedConfigs = config.getUnusedProperties();
+
+        Map<String, Object> avroProps = new HashMap<String, Object>();
+        avroProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, Utils.join(config.getList(WorkerConfig.BOOTSTRAP_SERVERS_CONFIG), ","));
+        avroProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, config.getClass(WorkerConfig.KEY_SERIALIZER_CLASS_CONFIG).getName());
+        avroProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, config.getClass(WorkerConfig.VALUE_SERIALIZER_CLASS_CONFIG).getName());
+        for (String propName : unusedConfigs.stringPropertyNames()) {
+            avroProps.put(propName, unusedConfigs.getProperty(propName));
+        }
+        producer = new KafkaProducer<Object, Object>(avroProps);
+
+        offsetBackingStore.start();
+        sourceTaskOffsetCommitter = new SourceTaskOffsetCommitter(time, config);
+
+        log.info("Worker started");
+    }
+
+    public void stop() {
+        log.info("Worker stopping");
+
+        long started = time.milliseconds();
+        long limit = started + config.getLong(WorkerConfig.TASK_SHUTDOWN_GRACEFUL_TIMEOUT_MS_CONFIG);
+
+        for (Map.Entry<ConnectorTaskId, WorkerTask> entry : tasks.entrySet()) {
+            WorkerTask task = entry.getValue();
+            log.warn("Shutting down task {} uncleanly; coordinator should have shut down "
+                    + "tasks before the Worker is stopped.", task);
+            try {
+                task.stop();
+            } catch (CopycatException e) {
+                log.error("Error while shutting down task " + task, e);
+            }
+        }
+
+        for (Map.Entry<ConnectorTaskId, WorkerTask> entry : tasks.entrySet()) {
+            WorkerTask task = entry.getValue();
+            log.debug("Waiting for task {} to finish shutting down", task);
+            if (!task.awaitStop(Math.max(limit - time.milliseconds(), 0))) {
+                log.error("Graceful shutdown of task {} failed.", task);
+            }
+            task.close();
+        }
+
+        long timeoutMs = limit - time.milliseconds();
+        sourceTaskOffsetCommitter.close(timeoutMs);
+
+        offsetBackingStore.start();
+
+        log.info("Worker stopped");
+    }
+
+    /**
+     * Add a new task.
+     * @param id Globally unique ID for this task.
+     * @param taskClassName name of the {@link org.apache.kafka.copycat.connector.Task}
+     *                      class to instantiate. Must be a subclass of either
+     *                      {@link org.apache.kafka.copycat.source.SourceTask} or
+     *                      {@link org.apache.kafka.copycat.sink.SinkTask}.
+     * @param props configuration options for the task
+     */
+    public void addTask(ConnectorTaskId id, String taskClassName, Properties props)
+            throws CopycatException {
+        if (tasks.containsKey(id)) {
+            String msg = "Task already exists in this worker; the coordinator should not have requested "
+                    + "that this : " + id;
+            log.error(msg);
+            throw new CopycatRuntimeException(msg);
+        }
+
+        final Task task = instantiateTask(taskClassName);
+
+        // Decide which type of worker task we need based on the type of task.
+        final WorkerTask workerTask;
+        if (task instanceof SourceTask) {
+            SourceTask sourceTask = (SourceTask) task;
+            OffsetStorageReader offsetReader
+                    = new OffsetStorageReaderImpl(offsetBackingStore, id.getConnector(), converter,
+                    offsetKeySerializer, offsetValueDeserializer);
+            OffsetStorageWriter offsetWriter
+                    = new OffsetStorageWriter(offsetBackingStore, id.getConnector(), converter,
+                    offsetKeySerializer, offsetValueSerializer);
+            workerTask = new WorkerSourceTask(id, sourceTask, converter, producer,
+                    offsetReader, offsetWriter,
+                    config, time);
+        } else if (task instanceof SinkTask) {
+            workerTask = new WorkerSinkTask(id, (SinkTask) task, config, converter, time);
+        } else {
+            log.error("Tasks must be a subclass of either SourceTask or SinkTask", task);
+            throw new CopycatException("Tasks must be a subclass of either SourceTask or SinkTask");
+        }
+
+        // Start the task before adding modifying any state, any exceptions are caught higher up the
+        // call chain and there's no cleanup to do here
+        workerTask.start(props);
+        tasks.put(id, workerTask);
+    }
+
+    private static Task instantiateTask(String taskClassName) {
+        return Reflection.instantiate(taskClassName, Task.class);
+    }
+
+    public void stopTask(ConnectorTaskId id) throws CopycatException {
+        WorkerTask task = getTask(id);
+        task.stop();
+        if (!task.awaitStop(config.getLong(WorkerConfig.TASK_SHUTDOWN_GRACEFUL_TIMEOUT_MS_CONFIG))) {
+            log.error("Graceful stop of task {} failed.", task);
+        }
+        task.close();
+        tasks.remove(id);
+    }
+
+    public ZkClient getZkClient() {
+        return zkClient;
+    }
+
+    private WorkerTask getTask(ConnectorTaskId id) {
+        WorkerTask task = tasks.get(id);
+        if (task == null) {
+            log.error("Task not found: " + id);
+            throw new CopycatRuntimeException();
+        }
+        return task;
+    }
+
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/WorkerSinkTask.java

@@ -0,0 +1,240 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.common.utils.Time;
+import org.apache.kafka.clients.consumer.*;
+import org.apache.kafka.common.utils.Utils;
+import org.apache.kafka.copycat.cli.WorkerConfig;
+import org.apache.kafka.copycat.connector.TopicPartition;
+import org.apache.kafka.copycat.errors.CopycatException;
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.apache.kafka.copycat.sink.SinkRecord;
+import org.apache.kafka.copycat.sink.SinkTask;
+import org.apache.kafka.copycat.sink.SinkTaskContext;
+import org.apache.kafka.copycat.storage.Converter;
+import org.apache.kafka.copycat.util.ConnectorTaskId;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.*;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * WorkerTask that uses a SinkTask to export data from Kafka.
+ */
+public class WorkerSinkTask implements WorkerTask {
+    private static final Logger log = LoggerFactory.getLogger(WorkerSinkTask.class);
+
+    private final ConnectorTaskId id;
+    private final SinkTask task;
+    private final WorkerConfig workerConfig;
+    private final Time time;
+    private final Converter converter;
+    private WorkerSinkTaskThread workThread;
+    private KafkaConsumer<Object, Object> consumer;
+    private final SinkTaskContext context;
+
+    public WorkerSinkTask(ConnectorTaskId id, SinkTask task, WorkerConfig workerConfig,
+                          Converter converter, Time time) {
+        this.id = id;
+        this.task = task;
+        this.workerConfig = workerConfig;
+        this.converter = converter;
+        context = new SinkTaskContextImpl();
+        this.time = time;
+    }
+
+    @Override
+    public void start(Properties props) {
+        task.initialize(context);
+        task.start(props);
+        consumer = createConsumer(props);
+        workThread = createWorkerThread();
+        workThread.start();
+    }
+
+    @Override
+    public void stop() throws CopycatException {
+        task.stop();
+        commitOffsets(time.milliseconds(), true, -1, false);
+        if (workThread != null) {
+            workThread.startGracefulShutdown();
+        }
+        // Closing the consumer has to wait until we're sure the work thread has exited so it won't
+        // call poll() anymore.
+    }
+
+    @Override
+    public boolean awaitStop(long timeoutMs) {
+        if (workThread != null) {
+            try {
+                boolean success = workThread.awaitShutdown(timeoutMs, TimeUnit.MILLISECONDS);
+                if (!success) {
+                    workThread.forceShutdown();
+                }
+                return success;
+            } catch (InterruptedException e) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    @Override
+    public void close() {
+        // FIXME Kafka needs to add a timeout parameter here for us to properly obey the timeout
+        // passed in
+        if (consumer != null) {
+            consumer.close();
+        }
+    }
+
+    /** Poll for new messages with the given timeout. Should only be invoked by the worker thread. */
+    public void poll(long timeoutMs) {
+        log.trace("{} polling consumer with timeout {} ms", id, timeoutMs);
+        ConsumerRecords<Object, Object> msgs = consumer.poll(timeoutMs);
+        log.trace("{} polling returned {} messages", id, msgs.count());
+        deliverMessages(msgs);
+    }
+
+    /**
+     * Starts an offset commit by flushing outstanding messages from the task and then starting
+     * the write commit. This should only be invoked by the WorkerSinkTaskThread.
+     **/
+    public void commitOffsets(long now, boolean sync, final int seqno, boolean flush) {
+        // Because of the different representations, we need to build two copies of the same map
+        HashMap<TopicPartition, Long> offsets = new HashMap<TopicPartition, Long>();
+        HashMap<org.apache.kafka.common.TopicPartition, Long> offsetsKafka
+                = new HashMap<org.apache.kafka.common.TopicPartition, Long>();
+        for (org.apache.kafka.common.TopicPartition tp : consumer.subscriptions()) {
+            long pos = consumer.position(tp);
+            offsets.put(new TopicPartition(tp.topic(), tp.partition()), pos);
+            offsetsKafka.put(tp, pos);
+        }
+        // We only don't flush the task in one case: when shutting down, the task has already been
+        // stopped and all data should have already been flushed
+        if (flush) {
+            try {
+                task.flush(offsets);
+            } catch (Throwable t) {
+                log.error("Commit of {} offsets failed due to exception while flushing: {}", this, t);
+                workThread.onCommitCompleted(t, seqno);
+                return;
+            }
+        }
+
+        ConsumerCommitCallback cb = new ConsumerCommitCallback() {
+            @Override
+            public void onComplete(Map<org.apache.kafka.common.TopicPartition, Long> offsets, Exception error) {
+                workThread.onCommitCompleted(error, seqno);
+            }
+        };
+        consumer.commit(offsetsKafka, sync ? CommitType.SYNC : CommitType.ASYNC, cb);
+    }
+
+    public Time getTime() {
+        return time;
+    }
+
+    public WorkerConfig getWorkerConfig() {
+        return workerConfig;
+    }
+
+    private KafkaConsumer<Object, Object> createConsumer(Properties taskProps) {
+        // Include any unknown worker configs so consumer configs can be set globally on the worker
+        // and through to the task
+        Properties props = workerConfig.getUnusedProperties();
+        props.setProperty(ConsumerConfig.GROUP_ID_CONFIG, "copycat-" + id.toString());
+        props.setProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,
+                Utils.join(workerConfig.getList(WorkerConfig.BOOTSTRAP_SERVERS_CONFIG), ","));
+        props.setProperty(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, "false");
+        props.setProperty(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
+        props.setProperty(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG,
+                workerConfig.getClass(WorkerConfig.KEY_DESERIALIZER_CLASS_CONFIG).getName());
+        props.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG,
+                workerConfig.getClass(WorkerConfig.VALUE_DESERIALIZER_CLASS_CONFIG).getName());
+
+        KafkaConsumer<Object, Object> newConsumer;
+        try {
+            newConsumer = new KafkaConsumer<Object, Object>(props);
+        } catch (Throwable t) {
+            throw new CopycatRuntimeException("Failed to create consumer", t);
+        }
+
+        List<TopicPartition> topicPartitions = getInputTopicPartitions(taskProps);
+        log.debug("Task {} subscribing to topic-partitions {}", id, topicPartitions);
+        Map<TopicPartition, Long> offsets = context.getOffsets();
+        for (TopicPartition tp : topicPartitions) {
+            org.apache.kafka.common.TopicPartition kafkatp = new
+                    org.apache.kafka.common.TopicPartition(tp.topic(), tp.partition());
+            newConsumer.subscribe(kafkatp);
+            if (offsets.containsKey(tp)) {
+                long offset = offsets.get(tp);
+                newConsumer.seek(kafkatp, offset);
+            }
+        }
+        return newConsumer;
+    }
+
+    private WorkerSinkTaskThread createWorkerThread() {
+        return new WorkerSinkTaskThread(this, "WorkerSinkTask-" + id, time, workerConfig);
+    }
+
+    private List<TopicPartition> getInputTopicPartitions(Properties taskProps) {
+        String topicPartitionsStr = taskProps.getProperty(SinkTask.TOPICPARTITIONS_CONFIG);
+        if (topicPartitionsStr == null || topicPartitionsStr.isEmpty()) {
+            throw new CopycatRuntimeException("Sink tasks require a list of topic partitions, which "
+                    + "copycat should generate automatically. This might "
+                    + "indicate your Task class inherits from SinkTask, but "
+                    + "your Connector class does not inherit from "
+                    + "SinkConnector.");
+        }
+
+        List<TopicPartition> topicPartitions = new ArrayList<TopicPartition>();
+        for (String topicPartitionStr : Arrays.asList(topicPartitionsStr.split(","))) {
+            topicPartitions.add(new TopicPartition(topicPartitionStr));
+        }
+        return topicPartitions;
+    }
+
+
+    private void deliverMessages(ConsumerRecords<Object, Object> msgs) {
+        // Finally, deliver this batch to the sink
+        if (msgs.count() > 0) {
+            List<SinkRecord> records = new ArrayList<SinkRecord>();
+            for (ConsumerRecord<Object, Object> msg : msgs) {
+                log.trace("Consuming message with key {}, value {}", msg.key(), msg.value());
+                records.add(
+                        new SinkRecord(msg.topic(), msg.partition(),
+                                converter.toCopycatData(msg.key()),
+                                converter.toCopycatData(msg.value()),
+                                msg.offset())
+                );
+            }
+
+            try {
+                task.put(records);
+            } catch (CopycatException e) {
+                log.error("Exception from SinkTask {}: ", id, e);
+            } catch (Throwable t) {
+                log.error("Unexpected exception from SinkTask {}: ", id, t);
+            }
+        }
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/WorkerSinkTaskThread.java

@@ -0,0 +1,110 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.common.utils.Time;
+import org.apache.kafka.copycat.cli.WorkerConfig;
+import org.apache.kafka.copycat.util.ShutdownableThread;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Worker thread for a WorkerSinkTask. These classes are very tightly coupled, but separated to
+ * simplify testing.
+ */
+class WorkerSinkTaskThread extends ShutdownableThread {
+    private static final Logger log = LoggerFactory.getLogger(WorkerSinkTask.class);
+
+    private final WorkerSinkTask task;
+    private long nextCommit;
+    private boolean committing;
+    private int commitSeqno;
+    private long commitStarted;
+    private int commitFailures;
+
+    public WorkerSinkTaskThread(WorkerSinkTask task, String name, Time time,
+                                WorkerConfig workerConfig) {
+        super(name);
+        this.task = task;
+        this.nextCommit = time.milliseconds() +
+                workerConfig.getLong(WorkerConfig.OFFSET_COMMIT_INTERVAL_MS_CONFIG);
+        this.committing = false;
+        this.commitSeqno = 0;
+        this.commitStarted = -1;
+        this.commitFailures = 0;
+    }
+
+    @Override
+    public void execute() {
+        while (getRunning()) {
+            iteration();
+        }
+    }
+
+    public void iteration() {
+        long now = task.getTime().milliseconds();
+
+        // Maybe commit
+        if (!committing && now >= nextCommit) {
+            synchronized (this) {
+                committing = true;
+                commitSeqno += 1;
+                commitStarted = now;
+            }
+            task.commitOffsets(now, false, commitSeqno, true);
+            nextCommit += task.getWorkerConfig().getLong(WorkerConfig.OFFSET_COMMIT_INTERVAL_MS_CONFIG);
+        }
+
+        // Check for timed out commits
+        long commitTimeout = commitStarted + task.getWorkerConfig().getLong(
+                WorkerConfig.OFFSET_COMMIT_TIMEOUT_MS_CONFIG);
+        if (committing && now >= commitTimeout) {
+            log.warn("Commit of {} offsets timed out", this);
+            commitFailures++;
+            committing = false;
+        }
+
+        // And process messages
+        long timeoutMs = Math.max(nextCommit - now, 0);
+        task.poll(timeoutMs);
+    }
+
+    public void onCommitCompleted(Throwable error, long seqno) {
+        synchronized (this) {
+            if (commitSeqno != seqno) {
+                log.debug("Got callback for timed out commit {}: {}, but most recent commit is {}",
+                        this,
+                        seqno, commitSeqno);
+            } else {
+                if (error != null) {
+                    log.error("Commit of {} offsets threw an unexpected exception: ", this, error);
+                    commitFailures++;
+                } else {
+                    log.debug("Finished {} offset commit successfully in {} ms",
+                            this, task.getTime().milliseconds() - commitStarted);
+                    commitFailures = 0;
+                }
+                committing = false;
+            }
+        }
+    }
+
+    public int getCommitFailures() {
+        return commitFailures;
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/WorkerSourceTask.java

@@ -0,0 +1,316 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.common.utils.Time;
+import org.apache.kafka.clients.producer.Callback;
+import org.apache.kafka.clients.producer.KafkaProducer;
+import org.apache.kafka.clients.producer.ProducerRecord;
+import org.apache.kafka.clients.producer.RecordMetadata;
+import org.apache.kafka.copycat.cli.WorkerConfig;
+import org.apache.kafka.copycat.errors.CopycatException;
+import org.apache.kafka.copycat.source.SourceRecord;
+import org.apache.kafka.copycat.source.SourceTask;
+import org.apache.kafka.copycat.source.SourceTaskContext;
+import org.apache.kafka.copycat.storage.Converter;
+import org.apache.kafka.copycat.storage.OffsetStorageReader;
+import org.apache.kafka.copycat.storage.OffsetStorageWriter;
+import org.apache.kafka.copycat.util.ConnectorTaskId;
+import org.apache.kafka.copycat.util.ShutdownableThread;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Properties;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+/**
+ * WorkerTask that uses a SourceTask to ingest data into Kafka.
+ */
+public class WorkerSourceTask implements WorkerTask {
+    private static final Logger log = LoggerFactory.getLogger(WorkerSourceTask.class);
+
+    private ConnectorTaskId id;
+    private SourceTask task;
+    private final Converter converter;
+    private KafkaProducer<Object, Object> producer;
+    private WorkerSourceTaskThread workThread;
+    private OffsetStorageReader offsetReader;
+    private OffsetStorageWriter offsetWriter;
+    private final WorkerConfig workerConfig;
+    private final Time time;
+
+    // Use IdentityHashMap to ensure correctness with duplicate records. This is a HashMap because
+    // there is no IdentityHashSet.
+    private IdentityHashMap<ProducerRecord<Object, Object>, ProducerRecord<Object, Object>>
+            outstandingMessages;
+    // A second buffer is used while an offset flush is running
+    private IdentityHashMap<ProducerRecord<Object, Object>, ProducerRecord<Object, Object>>
+            outstandingMessagesBacklog;
+    private boolean flushing;
+
+    public WorkerSourceTask(ConnectorTaskId id, SourceTask task,
+                            Converter converter,
+                            KafkaProducer<Object, Object> producer,
+                            OffsetStorageReader offsetReader, OffsetStorageWriter offsetWriter,
+                            WorkerConfig workerConfig, Time time) {
+        this.id = id;
+        this.task = task;
+        this.converter = converter;
+        this.producer = producer;
+        this.offsetReader = offsetReader;
+        this.offsetWriter = offsetWriter;
+        this.workerConfig = workerConfig;
+        this.time = time;
+
+        this.outstandingMessages
+                = new IdentityHashMap<ProducerRecord<Object, Object>, ProducerRecord<Object, Object>>();
+        this.outstandingMessagesBacklog
+                = new IdentityHashMap<ProducerRecord<Object, Object>, ProducerRecord<Object, Object>>();
+        this.flushing = false;
+    }
+
+    @Override
+    public void start(Properties props) {
+        task.initialize(new SourceTaskContext(offsetReader));
+        task.start(props);
+        workThread = new WorkerSourceTaskThread("WorkerSourceTask-" + id);
+        workThread.start();
+    }
+
+    @Override
+    public void stop() throws CopycatException {
+        task.stop();
+        commitOffsets();
+        if (workThread != null) {
+            workThread.startGracefulShutdown();
+        }
+    }
+
+    @Override
+    public boolean awaitStop(long timeoutMs) {
+        if (workThread != null) {
+            try {
+                boolean success = workThread.awaitShutdown(timeoutMs, TimeUnit.MILLISECONDS);
+                if (!success) {
+                    workThread.forceShutdown();
+                }
+                return success;
+            } catch (InterruptedException e) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    @Override
+    public void close() {
+        // Nothing to do
+    }
+
+    /**
+     * Send a batch of records. This is atomic up to the point of getting the messages into the
+     * Producer and recorded in our set of outstanding messages, so either all or none will be sent
+     * @param records
+     */
+    private synchronized void sendRecords(List<SourceRecord> records) {
+        for (SourceRecord record : records) {
+            final ProducerRecord<Object, Object> producerRecord
+                    = new ProducerRecord<Object, Object>(record.getTopic(), record.getPartition(),
+                    converter.fromCopycatData(record.getKey()),
+                    converter.fromCopycatData(record.getValue()));
+            log.trace("Appending record with key {}, value {}", record.getKey(), record.getValue());
+            if (!flushing) {
+                outstandingMessages.put(producerRecord, producerRecord);
+            } else {
+                outstandingMessagesBacklog.put(producerRecord, producerRecord);
+            }
+            producer.send(
+                    producerRecord,
+                    new Callback() {
+                        @Override
+                        public void onCompletion(RecordMetadata recordMetadata, Exception e) {
+                            if (e != null) {
+                                log.error("Failed to send record: ", e);
+                            } else {
+                                log.trace("Wrote record successfully: topic {} partition {} offset {}",
+                                        recordMetadata.topic(), recordMetadata.partition(),
+                                        recordMetadata.offset());
+                            }
+                            recordSent(producerRecord);
+                        }
+                    });
+            // Offsets are converted to Avro & serialized in the OffsetWriter
+            offsetWriter.setOffset(record.getStream(), record.getOffset());
+        }
+    }
+
+    private synchronized void recordSent(final ProducerRecord<Object, Object> record) {
+        ProducerRecord<Object, Object> removed = outstandingMessages.remove(record);
+        // While flushing, we may also see callbacks for items in the backlog
+        if (removed == null && flushing) {
+            removed = outstandingMessagesBacklog.remove(record);
+        }
+        // But if neither one had it, something is very wrong
+        if (removed == null) {
+            log.error("Saw callback for record that was not present in the outstanding message set: "
+                    + "{}", record);
+        } else if (flushing && outstandingMessages.isEmpty()) {
+            // flush thread may be waiting on the outstanding messages to clear
+            this.notifyAll();
+        }
+    }
+
+    public boolean commitOffsets() {
+        long commitTimeoutMs = workerConfig.getLong(WorkerConfig.OFFSET_COMMIT_TIMEOUT_MS_CONFIG);
+
+        long started = time.milliseconds();
+        long timeout = started + commitTimeoutMs;
+
+        synchronized (this) {
+            // First we need to make sure we snapshot everything in exactly the current state. This
+            // means both the current set of messages we're still waiting to finish, stored in this
+            // class, which setting flushing = true will handle by storing any new values into a new
+            // buffer; and the current set of user-specified offsets, stored in the
+            // OffsetStorageWriter, for which we can use beginFlush() to initiate the snapshot.
+            flushing = true;
+            boolean flushStarted = offsetWriter.beginFlush();
+            // Still wait for any producer records to flush, even if there aren't any offsets to write
+            // to persistent storage
+
+            // Next we need to wait for all outstanding messages to finish sending
+            while (!outstandingMessages.isEmpty()) {
+                try {
+                    long timeoutMs = timeout - time.milliseconds();
+                    if (timeoutMs <= 0) {
+                        log.error(
+                                "Failed to flush {}, timed out while waiting for producer to flush outstanding "
+                                        + "messages", this.toString());
+                        finishFailedFlush();
+                        return false;
+                    }
+                    this.wait(timeoutMs);
+                } catch (InterruptedException e) {
+                    // ignore
+                }
+            }
+
+            if (!flushStarted) {
+                // There was nothing in the offsets to process, but we still waited for the data in the
+                // buffer to flush. This is useful since this can feed into metrics to monitor, e.g.
+                // flush time, which can be used for monitoring even if the connector doesn't record any
+                // offsets.
+                finishSuccessfulFlush();
+                log.debug("Finished {} offset commitOffsets successfully in {} ms",
+                        this, time.milliseconds() - started);
+                return true;
+            }
+        }
+
+        // Now we can actually flush the offsets to user storage.
+        Future<Void> flushFuture = offsetWriter.doFlush(new org.apache.kafka.copycat.util.Callback<Void>() {
+            @Override
+            public void onCompletion(Throwable error, Void result) {
+                if (error != null) {
+                    log.error("Failed to flush {} offsets to storage: ", this, error);
+                } else {
+                    log.trace("Finished flushing {} offsets to storage", this);
+                }
+            }
+        });
+        // Very rare case: offsets were unserializable and we finished immediately, unable to store
+        // any data
+        if (flushFuture == null) {
+            finishFailedFlush();
+            return false;
+        }
+        try {
+            flushFuture.get(Math.max(timeout - time.milliseconds(), 0), TimeUnit.MILLISECONDS);
+            // There's a small race here where we can get the callback just as this times out (and log
+            // success), but then catch the exception below and cancel everything. This won't cause any
+            // errors, is only wasteful in this minor edge case, and the worst result is that the log
+            // could look a little confusing.
+        } catch (InterruptedException e) {
+            log.warn("Flush of {} offsets interrupted, cancelling", this);
+            finishFailedFlush();
+            return false;
+        } catch (ExecutionException e) {
+            log.error("Flush of {} offsets threw an unexpected exception: ", this, e);
+            finishFailedFlush();
+            return false;
+        } catch (TimeoutException e) {
+            log.error("Timed out waiting to flush {} offsets to storage", this);
+            finishFailedFlush();
+            return false;
+        }
+
+        finishSuccessfulFlush();
+        log.debug("Finished {} commitOffsets successfully in {} ms",
+                this, time.milliseconds() - started);
+        return true;
+    }
+
+    private synchronized void finishFailedFlush() {
+        offsetWriter.cancelFlush();
+        outstandingMessages.putAll(outstandingMessagesBacklog);
+        outstandingMessagesBacklog.clear();
+        flushing = false;
+    }
+
+    private void finishSuccessfulFlush() {
+        // If we were successful, we can just swap instead of replacing items back into the original map
+        IdentityHashMap<ProducerRecord<Object, Object>, ProducerRecord<Object, Object>> temp
+                = outstandingMessages;
+        outstandingMessages = outstandingMessagesBacklog;
+        outstandingMessagesBacklog = temp;
+        flushing = false;
+    }
+
+
+    private class WorkerSourceTaskThread extends ShutdownableThread {
+        public WorkerSourceTaskThread(String name) {
+            super(name);
+        }
+
+        @Override
+        public void execute() {
+            try {
+                while (getRunning()) {
+                    List<SourceRecord> records = task.poll();
+                    if (records == null) {
+                        continue;
+                    }
+                    sendRecords(records);
+                }
+            } catch (InterruptedException e) {
+                // Ignore and allow to exit.
+            }
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "WorkerSourceTask{" +
+                "id=" + id +
+                '}';
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/WorkerTask.java

@@ -0,0 +1,58 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.copycat.errors.CopycatException;
+
+import java.util.Properties;
+
+/**
+ * Handles processing for an individual task. This interface only provides the basic methods
+ * used by {@link Worker} to manage the tasks. Implementations combine a user-specified Task with
+ * Kafka to create a data flow.
+ */
+public interface WorkerTask {
+    /**
+     * Start the Task
+     * @param props initial configuration
+     */
+    void start(Properties props);
+
+    /**
+     * Stop this task from processing messages. This method does not block, it only triggers
+     * shutdown. Use #{@link #awaitStop} to block until completion.
+     *
+     * @throws CopycatException
+     */
+    void stop() throws CopycatException;
+
+    /**
+     * Wait for this task to finish stopping.
+     *
+     * @param timeoutMs
+     * @return true if successful, false if the timeout was reached
+     */
+    boolean awaitStop(long timeoutMs);
+
+    /**
+     * Close this task. This is different from #{@link #stop} and #{@link #awaitStop} in that the
+     * stop methods ensure processing has stopped but may leave resources allocated. This method
+     * should clean up all resources.
+     */
+    void close();
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/standalone/ConfigStorage.java

@@ -0,0 +1,60 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime.standalone;
+
+import java.util.Collection;
+import java.util.Properties;
+
+/**
+ * Interface used by StandaloneController to store configuration data for jobs. To be fault
+ * tolerant, all data required to resume jobs is stored here.
+ */
+public interface ConfigStorage {
+
+    /**
+     * Configure this storage engine.
+     * @param props configuration properties
+     */
+    void configure(Properties props);
+
+    /**
+     * Close this storage engine.
+     */
+    void close();
+
+    /**
+     * Commit the new connector config.
+     * @param connector
+     * @param properties
+     */
+    void putConnectorConfig(String connector, Properties properties);
+
+    /**
+     * Read back the config for the given connector.
+     * @param connector
+     * @return
+     */
+    Properties getConnectorConfig(String connector);
+
+    /**
+     * Get a list of connector names that have associated state in the store.
+     * @return
+     */
+    Collection<String> getConnectors();
+
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/standalone/FileConfigStorage.java

@@ -0,0 +1,110 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime.standalone;
+
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+
+import java.io.*;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+
+/**
+ * <p>
+ * Implementation of ConfigStorage that saves state to a local file. This allows a standalone
+ * node to tolerate faults/restarts.
+ * </p>
+ * <p>
+ * Currently the implementation is naive, inefficient, and only meant for testing or a small
+ * number of jobs.
+ * </p>
+ */
+public class FileConfigStorage implements ConfigStorage {
+    public static final String FILE_CONFIG = "config.storage.file";
+    public static final String FILE_DEFAULT = "configs.db";
+
+    private String filename;
+    private Map<String, Properties> connectorConfig = new HashMap<String, Properties>();
+
+    @Override
+    public void configure(Properties props) {
+        filename = props.getProperty(FILE_CONFIG);
+        if (filename == null)
+            filename = FILE_DEFAULT;
+        load();
+    }
+
+    @Override
+    public void close() {
+
+    }
+
+    @Override
+    public void putConnectorConfig(String connector, Properties properties) {
+        if (properties == null) {
+            connectorConfig.remove(connector);
+        } else {
+            connectorConfig.put(connector, properties);
+        }
+        save();
+    }
+
+    @Override
+    public Properties getConnectorConfig(String connector) {
+        return connectorConfig.get(connector);
+    }
+
+    @Override
+    public Collection<String> getConnectors() {
+        return connectorConfig.keySet();
+    }
+
+    /**
+     * Saves the current state to disk, overwriting previous data. This action is performed
+     * atomically.
+     */
+    private void save() {
+        try {
+            String tempFilename = filename + ".temp";
+            ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(tempFilename));
+            os.writeObject(connectorConfig);
+            os.close();
+
+            // Overwrite the original. Since the nio file package is JDK7+ only, this is the best we
+            // can do.
+            File tempFile = new File(tempFilename);
+            tempFile.renameTo(new File(filename));
+        } catch (IOException e) {
+            throw new CopycatRuntimeException("Failed to save config data to file", e);
+        }
+    }
+
+    private void load() {
+        try {
+            ObjectInputStream is = new ObjectInputStream(new FileInputStream(filename));
+            connectorConfig = (Map<String, Properties>) is.readObject();
+        } catch (FileNotFoundException e) {
+            // Expected on first run
+        } catch (IOException e) {
+            throw new CopycatRuntimeException("Failed to load config data", e);
+        } catch (ClassNotFoundException e) {
+            throw new CopycatRuntimeException("Failed to load config data", e);
+        }
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/standalone/StandaloneConnectorContext.java

@@ -0,0 +1,60 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime.standalone;
+
+import org.I0Itec.zkclient.ZkClient;
+import org.apache.kafka.copycat.connector.ConnectorContext;
+import org.apache.kafka.copycat.connector.TopicPartition;
+import org.apache.kafka.copycat.util.KafkaUtils;
+
+import java.util.List;
+
+/**
+ * ConnectorContext for use with the StandaloneCoordinator, which maintains all connectors and tasks
+ * in a single process.
+ */
+public class StandaloneConnectorContext implements ConnectorContext {
+
+    private StandaloneCoordinator coordinator;
+    private String connectorName;
+    private ZkClient zkClient;
+
+    public StandaloneConnectorContext(StandaloneCoordinator coordinator, String connectorName,
+                                      ZkClient zkClient) {
+        this.coordinator = coordinator;
+        this.connectorName = connectorName;
+        this.zkClient = zkClient;
+    }
+
+    @Override
+    public void requestTaskReconfiguration() {
+        // This is trivial to forward since there is only one coordinator and it's in memory in this
+        // process
+        coordinator.requestTaskReconfiguration(connectorName);
+    }
+
+    @Override
+    public List<TopicPartition> getTopicPartitions(String... topics) {
+        return KafkaUtils.getTopicPartitions(zkClient, topics);
+    }
+
+    @Override
+    public List<TopicPartition> getTopicPartitions(List<String> topics) {
+        return KafkaUtils.getTopicPartitions(zkClient, topics);
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/runtime/standalone/StandaloneCoordinator.java

@@ -0,0 +1,315 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime.standalone;
+
+import org.apache.kafka.common.utils.Utils;
+import org.apache.kafka.copycat.connector.Connector;
+import org.apache.kafka.copycat.connector.TopicPartition;
+import org.apache.kafka.copycat.errors.CopycatException;
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.apache.kafka.copycat.runtime.ConnectorConfig;
+import org.apache.kafka.copycat.runtime.Coordinator;
+import org.apache.kafka.copycat.runtime.Worker;
+import org.apache.kafka.copycat.sink.SinkConnector;
+import org.apache.kafka.copycat.sink.SinkTask;
+import org.apache.kafka.copycat.util.*;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.*;
+
+/**
+ * Single process, in-memory "coordinator". Useful for a standalone copycat process.
+ */
+public class StandaloneCoordinator implements Coordinator {
+    private static final Logger log = LoggerFactory.getLogger(StandaloneCoordinator.class);
+
+    public static final String STORAGE_CONFIG = "coordinator.standalone.storage";
+
+    private Worker worker;
+    private Properties configs;
+    private ConfigStorage configStorage;
+    private HashMap<String, ConnectorState> connectors = new HashMap<String, ConnectorState>();
+
+    public StandaloneCoordinator(Worker worker, Properties props) {
+        this.worker = worker;
+        this.configs = props;
+    }
+
+    public synchronized void start() {
+        log.info("Coordinator starting");
+
+        String storage = configs.getProperty(STORAGE_CONFIG);
+        if (storage != null && !storage.isEmpty()) {
+            configStorage = Reflection.instantiate(storage, ConfigStorage.class);
+            configStorage.configure(configs);
+        } else {
+            configStorage = null;
+        }
+
+        restoreConnectors();
+
+        log.info("Coordinator started");
+    }
+
+    public synchronized void stop() {
+        log.info("Coordinator stopping");
+
+        // There's no coordination/hand-off to do here since this is all standalone. Instead, we
+        // should just clean up the stuff we normally would, i.e. cleanly checkpoint and shutdown all
+        // the tasks.
+        for (Map.Entry<String, ConnectorState> entry : connectors.entrySet()) {
+            ConnectorState state = entry.getValue();
+            stopConnector(state);
+        }
+        connectors.clear();
+
+        if (configStorage != null) {
+            configStorage.close();
+            configStorage = null;
+        }
+
+        log.info("Coordinator stopped");
+    }
+
+    @Override
+    public synchronized void addConnector(Properties connectorProps,
+                                          Callback<String> callback) {
+        try {
+            ConnectorState connState = createConnector(connectorProps);
+            if (callback != null) {
+                callback.onCompletion(null, connState.name);
+            }
+            // This should always be a new job, create jobs from scratch
+            createConnectorTasks(connState);
+        } catch (CopycatRuntimeException e) {
+            if (callback != null) {
+                callback.onCompletion(e, null);
+            }
+        }
+    }
+
+    @Override
+    public synchronized void deleteConnector(String name, Callback<Void> callback) {
+        try {
+            destroyConnector(name);
+            if (callback != null) {
+                callback.onCompletion(null, null);
+            }
+        } catch (CopycatRuntimeException e) {
+            if (callback != null) {
+                callback.onCompletion(e, null);
+            }
+        }
+    }
+
+    // Creates the and configures the connector. Does not setup any tasks
+    private ConnectorState createConnector(Properties connectorProps) {
+        ConnectorConfig connConfig = new ConnectorConfig(connectorProps);
+        String connName = connConfig.getString(ConnectorConfig.NAME_CONFIG);
+        String className = connConfig.getString(ConnectorConfig.CONNECTOR_CLASS_CONFIG);
+        log.info("Creating connector {} of type {}", connName, className);
+        int maxTasks = connConfig.getInt(ConnectorConfig.TASKS_MAX_CONFIG);
+        List<String> topics = connConfig.getList(ConnectorConfig.TOPICS_CONFIG); // Sinks only
+        Properties configs = connConfig.getUnusedProperties();
+
+        if (connectors.containsKey(connName)) {
+            log.error("Ignoring request to create connector due to conflicting connector name");
+            throw new CopycatRuntimeException("Connector with name " + connName + " already exists");
+        }
+
+        final Connector connector;
+        try {
+            connector = instantiateConnector(className);
+        } catch (Throwable t) {
+            // Catches normal exceptions due to instantiation errors as well as any runtime errors that
+            // may be caused by user code
+            throw new CopycatRuntimeException("Failed to create connector instance", t);
+        }
+        connector.initialize(new StandaloneConnectorContext(this, connName, worker.getZkClient()));
+        try {
+            connector.start(configs);
+        } catch (CopycatException e) {
+            throw new CopycatRuntimeException("Connector threw an exception while starting", e);
+        }
+        ConnectorState state = new ConnectorState(connName, connector, maxTasks, topics);
+        connectors.put(connName, state);
+        if (configStorage != null) {
+            configStorage.putConnectorConfig(connName, connectorProps);
+        }
+
+        log.info("Finished creating connector {}", connName);
+
+        return state;
+    }
+
+    private static Connector instantiateConnector(String className) {
+        return Reflection.instantiate(className, Connector.class);
+    }
+
+    private void destroyConnector(String connName) {
+        log.info("Destroying connector {}", connName);
+        ConnectorState state = connectors.get(connName);
+        if (state == null) {
+            log.error("Failed to destroy connector {} because it does not exist", connName);
+            throw new CopycatRuntimeException("Connector does not exist");
+        }
+
+        stopConnector(state);
+        connectors.remove(state.name);
+        if (configStorage != null) {
+            configStorage.putConnectorConfig(state.name, null);
+        }
+
+        log.info("Finished destroying connector {}", connName);
+    }
+
+    // Stops a connectors tasks, then the connector
+    private void stopConnector(ConnectorState state) {
+        removeConnectorTasks(state);
+        try {
+            state.connector.stop();
+        } catch (CopycatException e) {
+            log.error("Error shutting down connector {}: ", state.connector, e);
+        }
+    }
+
+    private void createConnectorTasks(ConnectorState state) {
+        String taskClassName = state.connector.getTaskClass().getName();
+
+        log.info("Creating tasks for connector {} of type {}", state.name, taskClassName);
+
+        int maxTasks = state.maxTasks;
+        // For sink tasks, we may also be limited by the number of input topic partitions
+        List<TopicPartition> topicPartitions = null;
+        if (state.connector instanceof SinkConnector) {
+            topicPartitions = KafkaUtils.getTopicPartitions(worker.getZkClient(), state.inputTopics);
+            maxTasks = Math.min(maxTasks, topicPartitions.size());
+        }
+        List<Properties> taskConfigs = state.connector.getTaskConfigs(maxTasks);
+
+        // If necessary, figure out how to distribute input topic partitions
+        // TODO: This needs to run periodically so we detect new partitions
+        List<List<TopicPartition>> taskAssignments = null;
+        if (state.connector instanceof SinkConnector) {
+            taskAssignments = ConnectorUtils.groupPartitions(topicPartitions, taskConfigs.size());
+        }
+
+        // Generate the final configs, including framework provided settings
+        Map<ConnectorTaskId, Properties> taskProps = new HashMap<ConnectorTaskId, Properties>();
+        for (int i = 0; i < taskConfigs.size(); i++) {
+            ConnectorTaskId taskId = new ConnectorTaskId(state.name, i);
+            Properties config = taskConfigs.get(i);
+            if (state.connector instanceof SinkConnector) {
+                // Make sure we don't modify the original since the connector may reuse it internally
+                Properties configForSink = new Properties();
+                configForSink.putAll(config);
+                configForSink.setProperty(SinkTask.TOPICPARTITIONS_CONFIG, Utils.join(taskAssignments.get(i), ","));
+                config = configForSink;
+            }
+            taskProps.put(taskId, config);
+        }
+
+        // And initiate the tasks
+        for (int i = 0; i < taskConfigs.size(); i++) {
+            ConnectorTaskId taskId = new ConnectorTaskId(state.name, i);
+            Properties config = taskProps.get(taskId);
+            try {
+                worker.addTask(taskId, taskClassName, config);
+                // We only need to store the task IDs so we can clean up.
+                state.tasks.add(taskId);
+            } catch (Throwable e) {
+                log.error("Failed to add task {}: ", taskId, e);
+                // Swallow this so we can continue updating the rest of the tasks
+                // FIXME what's the proper response? Kill all the tasks? Consider this the same as a task
+                // that died after starting successfully.
+            }
+        }
+    }
+
+    private void removeConnectorTasks(ConnectorState state) {
+        Iterator<ConnectorTaskId> taskIter = state.tasks.iterator();
+        while (taskIter.hasNext()) {
+            ConnectorTaskId taskId = taskIter.next();
+            try {
+                worker.stopTask(taskId);
+                taskIter.remove();
+            } catch (CopycatException e) {
+                log.error("Failed to stop task {}: ", taskId, e);
+                // Swallow this so we can continue stopping the rest of the tasks
+                // FIXME: Forcibly kill the task?
+            }
+        }
+    }
+
+    private void updateConnectorTasks(ConnectorState state) {
+        removeConnectorTasks(state);
+        createConnectorTasks(state);
+    }
+
+    private void restoreConnectors() {
+        if (configStorage == null) {
+            return;
+        }
+
+        Collection<String> connNames = configStorage.getConnectors();
+        for (String connName : connNames) {
+            log.info("Restoring connector {}", connName);
+            Properties connProps = configStorage.getConnectorConfig(connName);
+            ConnectorState connState = createConnector(connProps);
+            // Because this coordinator is standalone, connectors are only restored when this process
+            // starts and we know there can't be any existing tasks. So in this special case we're able
+            // to just create the tasks rather than having to check for existing tasks and sort out
+            // whether they need to be reconfigured.
+            createConnectorTasks(connState);
+        }
+    }
+
+    /**
+     * Requests reconfiguration of the task. This should only be triggered by
+     * {@link StandaloneConnectorContext}.
+     *
+     * @param connName name of the connector that should be reconfigured
+     */
+    public synchronized void requestTaskReconfiguration(String connName) {
+        ConnectorState state = connectors.get(connName);
+        if (state == null) {
+            log.error("Task that requested reconfiguration does not exist: {}", connName);
+            return;
+        }
+        updateConnectorTasks(state);
+    }
+
+
+    private static class ConnectorState {
+        public String name;
+        public Connector connector;
+        public int maxTasks;
+        public List<String> inputTopics;
+        Set<ConnectorTaskId> tasks;
+
+        public ConnectorState(String name, Connector connector, int maxTasks,
+                              List<String> inputTopics) {
+            this.name = name;
+            this.connector = connector;
+            this.maxTasks = maxTasks;
+            this.inputTopics = inputTopics;
+            this.tasks = new HashSet<ConnectorTaskId>();
+        }
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/storage/FileOffsetBackingStore.java

@@ -0,0 +1,112 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.storage;
+
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.*;
+import java.nio.ByteBuffer;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+
+/**
+ * Implementation of OffsetBackingStore that saves data locally to a file. To ensure this behaves
+ * similarly to a real backing store, operations are executed asynchronously on a background thread.
+ */
+public class FileOffsetBackingStore extends MemoryOffsetBackingStore {
+    private static final Logger log = LoggerFactory.getLogger(FileOffsetBackingStore.class);
+
+    public final static String OFFSET_STORAGE_FILE_FILENAME_CONFIG = "offset.storage.file.filename";
+    private File file;
+
+    public FileOffsetBackingStore() {
+
+    }
+
+    @Override
+    public void configure(Properties props) {
+        super.configure(props);
+        String filename = props.getProperty(OFFSET_STORAGE_FILE_FILENAME_CONFIG);
+        file = new File(filename);
+    }
+
+    @Override
+    public synchronized void start() {
+        super.start();
+        log.info("Starting FileOffsetBackingStore with file {}", file);
+        load();
+    }
+
+    @Override
+    public synchronized void stop() {
+        super.stop();
+        // Nothing to do since this doesn't maintain any outstanding connections/data
+        log.info("Stopped FileOffsetBackingStore");
+    }
+
+    private void load() {
+        try {
+            ObjectInputStream is = new ObjectInputStream(new FileInputStream(file));
+            HashMap<String, Map<byte[], byte[]>> raw
+                    = (HashMap<String, Map<byte[], byte[]>>) is.readObject();
+            data = new HashMap<String, Map<ByteBuffer, ByteBuffer>>();
+            for (Map.Entry<String, Map<byte[], byte[]>> entry : raw.entrySet()) {
+                HashMap<ByteBuffer, ByteBuffer> converted = new HashMap<ByteBuffer, ByteBuffer>();
+                for (Map.Entry<byte[], byte[]> mapEntry : entry.getValue().entrySet()) {
+                    ByteBuffer key = (mapEntry.getKey() != null) ? ByteBuffer.wrap(mapEntry.getKey()) : null;
+                    ByteBuffer value = (mapEntry.getValue() != null) ? ByteBuffer.wrap(mapEntry.getValue()) :
+                            null;
+                    converted.put(key, value);
+                }
+                data.put(entry.getKey(), converted);
+            }
+            is.close();
+        } catch (FileNotFoundException e) {
+            // Ignore, may be new
+        } catch (EOFException e) {
+            // Ignore, this means the file was missing or corrupt
+        } catch (IOException e) {
+            throw new CopycatRuntimeException(e);
+        } catch (ClassNotFoundException e) {
+            throw new CopycatRuntimeException(e);
+        }
+    }
+
+    protected void save() {
+        try {
+            ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(file));
+            HashMap<String, Map<byte[], byte[]>> raw = new HashMap<String, Map<byte[], byte[]>>();
+            for (Map.Entry<String, Map<ByteBuffer, ByteBuffer>> entry : data.entrySet()) {
+                HashMap<byte[], byte[]> converted = new HashMap<byte[], byte[]>();
+                for (Map.Entry<ByteBuffer, ByteBuffer> mapEntry : entry.getValue().entrySet()) {
+                    byte[] key = (mapEntry.getKey() != null) ? mapEntry.getKey().array() : null;
+                    byte[] value = (mapEntry.getValue() != null) ? mapEntry.getValue().array() : null;
+                    converted.put(key, value);
+                }
+                raw.put(entry.getKey(), converted);
+            }
+            os.writeObject(raw);
+            os.close();
+        } catch (IOException e) {
+            throw new CopycatRuntimeException(e);
+        }
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/storage/MemoryOffsetBackingStore.java

@@ -0,0 +1,117 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.storage;
+
+import org.apache.kafka.copycat.util.Callback;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+/**
+ * Implementation of OffsetBackingStore that doesn't actually persist any data. To ensure this
+ * behaves similarly to a real backing store, operations are executed asynchronously on a
+ * background thread.
+ */
+public class MemoryOffsetBackingStore implements OffsetBackingStore {
+    private static final Logger log = LoggerFactory.getLogger(MemoryOffsetBackingStore.class);
+
+    protected HashMap<String, Map<ByteBuffer, ByteBuffer>> data = new HashMap<String, Map<ByteBuffer, ByteBuffer>>();
+    protected ExecutorService executor = Executors.newSingleThreadExecutor();
+
+    public MemoryOffsetBackingStore() {
+
+    }
+
+    @Override
+    public void configure(Properties props) {
+    }
+
+    @Override
+    public synchronized void start() {
+    }
+
+    @Override
+    public synchronized void stop() {
+        // Nothing to do since this doesn't maintain any outstanding connections/data
+    }
+
+    @Override
+    public Future<Map<ByteBuffer, ByteBuffer>> get(
+            final String namespace, final Collection<ByteBuffer> keys,
+            final Callback<Map<ByteBuffer, ByteBuffer>> callback) {
+        return executor.submit(new Callable<Map<ByteBuffer, ByteBuffer>>() {
+            @Override
+            public Map<ByteBuffer, ByteBuffer> call() throws Exception {
+                Map<ByteBuffer, ByteBuffer> result = new HashMap<ByteBuffer, ByteBuffer>();
+                synchronized (MemoryOffsetBackingStore.this) {
+                    Map<ByteBuffer, ByteBuffer> namespaceData = data.get(namespace);
+                    if (namespaceData == null) {
+                        return result;
+                    }
+                    for (ByteBuffer key : keys) {
+                        result.put(key, namespaceData.get(key));
+                    }
+                }
+                if (callback != null) {
+                    callback.onCompletion(null, result);
+                }
+                return result;
+            }
+        });
+
+    }
+
+    @Override
+    public Future<Void> set(final String namespace, final Map<ByteBuffer, ByteBuffer> values,
+                            final Callback<Void> callback) {
+        return executor.submit(new Callable<Void>() {
+            @Override
+            public Void call() throws Exception {
+                synchronized (MemoryOffsetBackingStore.this) {
+                    Map<ByteBuffer, ByteBuffer> namespaceData = data.get(namespace);
+                    if (namespaceData == null) {
+                        namespaceData = new HashMap<ByteBuffer, ByteBuffer>();
+                        data.put(namespace, namespaceData);
+                    }
+                    for (Map.Entry<ByteBuffer, ByteBuffer> entry : values.entrySet()) {
+                        namespaceData.put(entry.getKey(), entry.getValue());
+                    }
+                    save();
+                }
+                if (callback != null) {
+                    callback.onCompletion(null, null);
+                }
+                return null;
+            }
+        });
+    }
+
+    // Hook to allow subclasses to persist data
+    protected void save() {
+
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/storage/OffsetBackingStore.java

@@ -0,0 +1,74 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.storage;
+
+import org.apache.kafka.copycat.util.Callback;
+import org.apache.kafka.copycat.util.Configurable;
+
+import java.nio.ByteBuffer;
+import java.util.Collection;
+import java.util.Map;
+import java.util.concurrent.Future;
+
+/**
+ * <p>
+ * OffsetBackingStore is an interface for storage backends that store key-value data. The backing
+ * store doesn't need to handle serialization or deserialization. It only needs to support
+ * reading/writing bytes. Since it is expected these operations will require network
+ * operations, only bulk operations are supported.
+ * </p>
+ * <p>
+ * Since OffsetBackingStore is a shared resource that may be used by many OffsetStorage instances
+ * that are associated with individual tasks, all operations include a namespace which should be
+ * used to isolate different key spaces.
+ * </p>
+ */
+public interface OffsetBackingStore extends Configurable {
+
+    /**
+     * Start this offset store.
+     */
+    public void start();
+
+    /**
+     * Stop the backing store. Implementations should attempt to shutdown gracefully, but not block
+     * indefinitely.
+     */
+    public void stop();
+
+    /**
+     * Get the values for the specified keys
+     * @param namespace prefix for the keys in this request
+     * @param keys list of keys to look up
+     * @param callback callback to invoke on completion
+     * @return future for the resulting map from key to value
+     */
+    public Future<Map<ByteBuffer, ByteBuffer>> get(
+            String namespace, Collection<ByteBuffer> keys,
+            Callback<Map<ByteBuffer, ByteBuffer>> callback);
+
+    /**
+     * Set the specified keys and values.
+     * @param namespace prefix for the keys in this request
+     * @param values map from key to value
+     * @param callback callback to invoke on completion
+     * @return void future for the operation
+     */
+    public Future<Void> set(String namespace, Map<ByteBuffer, ByteBuffer> values,
+                            Callback<Void> callback);
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/storage/OffsetStorageReaderImpl.java

@@ -0,0 +1,113 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.storage;
+
+import org.apache.kafka.copycat.data.Schema;
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Implementation of OffsetStorageReader. Unlike OffsetStorageWriter which is implemented
+ * directly, the interface is only separate from this implementation because it needs to be
+ * included in the public API package.
+ */
+public class OffsetStorageReaderImpl implements OffsetStorageReader {
+    private static final Logger log = LoggerFactory.getLogger(OffsetStorageReaderImpl.class);
+
+    private final OffsetBackingStore backingStore;
+    private final String namespace;
+    private final Converter converter;
+    private final OffsetSerializer keySerializer;
+    private final OffsetDeserializer valueDeserializer;
+
+    public OffsetStorageReaderImpl(OffsetBackingStore backingStore, String namespace,
+                                   Converter converter,
+                                   OffsetSerializer keySerializer,
+                                   OffsetDeserializer valueDeserializer) {
+        this.backingStore = backingStore;
+        this.namespace = namespace;
+        this.converter = converter;
+        this.keySerializer = keySerializer;
+        this.valueDeserializer = valueDeserializer;
+    }
+
+    @Override
+    public Object getOffset(Object stream, Schema schema) {
+        return getOffsets(Arrays.asList(stream), schema).get(stream);
+    }
+
+    @Override
+    public Map<Object, Object> getOffsets(Collection<Object> streams, Schema schema) {
+        // Serialize keys so backing store can work with them
+        Map<ByteBuffer, Object> serializedToOriginal = new HashMap<ByteBuffer, Object>(streams.size());
+        for (Object key : streams) {
+            try {
+                byte[] keySerialized = keySerializer.serializeOffset(namespace,
+                        converter.fromCopycatData(key));
+                ByteBuffer keyBuffer = (keySerialized != null) ? ByteBuffer.wrap(keySerialized) : null;
+                serializedToOriginal.put(keyBuffer, key);
+            } catch (Throwable t) {
+                log.error("CRITICAL: Failed to serialize stream key when getting offsets for task with "
+                        + "namespace {}. No value for this data will be returned, which may break the "
+                        + "task or cause it to skip some data.", namespace, t);
+            }
+        }
+
+        // Get serialized key -> serialized value from backing store
+        Map<ByteBuffer, ByteBuffer> raw;
+        try {
+            raw = backingStore.get(namespace, serializedToOriginal.keySet(), null).get();
+        } catch (Exception e) {
+            log.error("Failed to fetch offsets from namespace {}: ", namespace, e);
+            throw new CopycatRuntimeException("Failed to fetch offsets.", e);
+        }
+
+        // Deserialize all the values and map back to the original keys
+        Map<Object, Object> result = new HashMap<Object, Object>(streams.size());
+        for (Map.Entry<ByteBuffer, ByteBuffer> rawEntry : raw.entrySet()) {
+            try {
+                // Since null could be a valid key, explicitly check whether map contains the key
+                if (!serializedToOriginal.containsKey(rawEntry.getKey())) {
+                    log.error("Should be able to map {} back to a requested stream-offset key, backing "
+                            + "store may have returned invalid data", rawEntry.getKey());
+                    continue;
+                }
+                Object origKey = serializedToOriginal.get(rawEntry.getKey());
+                Object deserializedValue = converter.toCopycatData(
+                        valueDeserializer.deserializeOffset(namespace, rawEntry.getValue().array(), schema)
+                );
+
+                result.put(origKey, deserializedValue);
+            } catch (Throwable t) {
+                log.error("CRITICAL: Failed to deserialize offset data when getting offsets for task with"
+                        + " namespace {}. No value for this data will be returned, which may break the "
+                        + "task or cause it to skip some data. This could either be due to an error in "
+                        + "the connector implementation or incompatible schema.", namespace, t);
+            }
+        }
+
+        return result;
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/storage/OffsetStorageWriter.java

@@ -0,0 +1,204 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.storage;
+
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.apache.kafka.copycat.util.Callback;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.nio.ByteBuffer;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.Future;
+
+/**
+ * <p>
+ * OffsetStorageWriter is a buffered writer that wraps the simple OffsetBackingStore interface.
+ * It maintains a copy of the key-value data in memory and buffers writes. It allows you to take
+ * a snapshot, which can then be asynchronously flushed to the backing store while new writes
+ * continue to be processed. This allows Copycat to process offset commits in the background
+ * while continuing to process messages.
+ * </p>
+ * <p>
+ * Copycat uses an OffsetStorage implementation to save state about the current progress of
+ * source (import to Kafka) jobs, which may have many input streams and "offsets" may not be as
+ * simple as they are for Kafka partitions or files. Offset storage is not required for sink jobs
+ * because they can use Kafka's native offset storage (or the sink data store can handle offset
+ * storage to achieve exactly once semantics).
+ * </p>
+ * <p>
+ * Both streams and offsets are generic data objects. This allows different connectors to use
+ * whatever representation they need, even arbitrarily complex records. These are translated
+ * internally into the serialized form the OffsetBackingStore uses.
+ * </p>
+ * <p>
+ * Note that this only provides write functionality. This is intentional to ensure stale data is
+ * never read. Offset data should only be read during startup or reconfiguration of a task. By
+ * always serving those requests by reading the values from the backing store, we ensure we never
+ * accidentally use stale data. (One example of how this can occur: a task is processing input
+ * stream A, writing offsets; reconfiguration causes stream A to be reassigned elsewhere;
+ * reconfiguration causes stream A to be reassigned to this node, but now the offset data is out
+ * of date). Since these offsets are created and managed by the connector itself, there's no way
+ * for the offset management layer to know which keys are "owned" by which tasks at any given
+ * time.
+ * </p>
+ * <p>
+ * This class is not thread-safe. It should only be accessed from a Task's processing thread.
+ * </p>
+ */
+public class OffsetStorageWriter {
+    private static final Logger log = LoggerFactory.getLogger(OffsetStorageWriter.class);
+
+    private final OffsetBackingStore backingStore;
+    private final Converter converter;
+    private final OffsetSerializer keySerializer;
+    private final OffsetSerializer valueSerializer;
+    private final String namespace;
+    private Map<Object, Object> data = new HashMap<Object, Object>();
+
+    // Not synchronized, should only be accessed by flush thread
+    private Map<Object, Object> toFlush = null;
+    // Unique ID for each flush request to handle callbacks after timeouts
+    private long currentFlushId = 0;
+
+    public OffsetStorageWriter(OffsetBackingStore backingStore,
+                               String namespace, Converter converter,
+                               OffsetSerializer keySerializer, OffsetSerializer valueSerializer) {
+        this.backingStore = backingStore;
+        this.namespace = namespace;
+        this.converter = converter;
+        this.keySerializer = keySerializer;
+        this.valueSerializer = valueSerializer;
+    }
+
+    public synchronized void setOffset(Object stream, Object offset) {
+        data.put(stream, offset);
+    }
+
+    private boolean flushing() {
+        return toFlush != null;
+    }
+
+    /**
+     * Performs the first step of a flush operation, snapshotting the current state. This does not
+     * actually initiate the flush with the underlying storage.
+     *
+     * @return true if a flush was initiated, false if no data was available
+     */
+    public synchronized boolean beginFlush() {
+        if (flushing()) {
+            log.error("Invalid call to OffsetStorageWriter flush() while already flushing, the "
+                    + "framework should not allow this");
+            throw new CopycatRuntimeException("OffsetStorageWriter is already flushing");
+        }
+
+        if (data.isEmpty()) {
+            return false;
+        }
+
+        assert !flushing();
+        toFlush = data;
+        data = new HashMap<Object, Object>();
+        return true;
+    }
+
+    /**
+     * Flush the current offsets and clear them from this writer. This is non-blocking: it
+     * moves the current set of offsets out of the way, serializes the data, and asynchronously
+     * writes the data to the backing store. If no offsets need to be written, the callback is
+     * still invoked, but no Future is returned.
+     *
+     * @return a Future, or null if there are no offsets to commitOffsets
+     */
+    public Future<Void> doFlush(final Callback<Void> callback) {
+        final long flushId = currentFlushId;
+
+        // Serialize
+        Map<ByteBuffer, ByteBuffer> offsetsSerialized;
+        try {
+            offsetsSerialized = new HashMap<ByteBuffer, ByteBuffer>();
+            for (Map.Entry<Object, Object> entry : toFlush.entrySet()) {
+                byte[] key = keySerializer.serializeOffset(namespace,
+                        converter.fromCopycatData(entry.getKey()));
+                ByteBuffer keyBuffer = (key != null) ? ByteBuffer.wrap(key) : null;
+                byte[] value = valueSerializer.serializeOffset(namespace,
+                        converter.fromCopycatData(entry.getValue()));
+                ByteBuffer valueBuffer = (value != null) ? ByteBuffer.wrap(value) : null;
+                offsetsSerialized.put(keyBuffer, valueBuffer);
+            }
+        } catch (Throwable t) {
+            // Must handle errors properly here or the writer will be left mid-flush forever and be
+            // unable to make progress.
+            log.error("CRITICAL: Failed to serialize offset data, making it impossible to commit "
+                    + "offsets under namespace {}. This likely won't recover unless the "
+                    + "unserializable stream or offset information is overwritten.", namespace);
+            callback.onCompletion(t, null);
+            return null;
+        }
+
+        // And submit the data
+        log.debug("Submitting {} entries to backing store", offsetsSerialized.size());
+        return backingStore.set(namespace, offsetsSerialized, new Callback<Void>() {
+            @Override
+            public void onCompletion(Throwable error, Void result) {
+                boolean isCurrent = handleFinishWrite(flushId, error, result);
+                if (isCurrent && callback != null) {
+                    callback.onCompletion(error, result);
+                }
+            }
+        });
+    }
+
+    /**
+     * Cancel a flush that has been initiated by {@link #beginFlush}. This should not be called if
+     * {@link #doFlush} has already been invoked. It should be used if an operation performed
+     * between beginFlush and doFlush failed.
+     */
+    public synchronized void cancelFlush() {
+        // Verify we're still flushing data to handle a race between cancelFlush() calls from up the
+        // call stack and callbacks from the write request to underlying storage
+        if (flushing()) {
+            // Just recombine the data and place it back in the primary storage
+            toFlush.putAll(data);
+            data = toFlush;
+            currentFlushId++;
+            toFlush = null;
+        }
+    }
+
+    /**
+     * Handle completion of a write. Returns true if this callback is for the current flush
+     * operation, false if it's for an old operation that should now be ignored.
+     */
+    private synchronized boolean handleFinishWrite(long flushId, Throwable error, Void result) {
+        // Callbacks need to be handled carefully since the flush operation may have already timed
+        // out and been cancelled.
+        if (flushId != currentFlushId) {
+            return false;
+        }
+
+        if (error != null) {
+            cancelFlush();
+        } else {
+            currentFlushId++;
+            toFlush = null;
+        }
+        return true;
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/util/Callback.java

@@ -0,0 +1,31 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.util;
+
+/**
+ * Generic interface for callbacks
+ */
+public interface Callback<V> {
+    /**
+     * Invoked upon completion of the operation.
+     *
+     * @param error the error that caused the operation to fail, or null if no error occurred
+     * @param result the return value, or null if the operation failed
+     */
+    void onCompletion(Throwable error, V result);
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/util/Configurable.java

@@ -5,9 +5,9 @@
  * The ASF licenses this file to You under the Apache License, Version 2.0
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -17,22 +17,11 @@
 
 package org.apache.kafka.copycat.util;
 
-import org.junit.Test;
+import java.util.Properties;
 
-import java.util.Arrays;
-import java.util.Collections;
-
-import static org.junit.Assert.assertEquals;
-
-public class StringUtilsTest {
-
-    @Test
-    public void testJoin() {
-        assertEquals("", StringUtils.join(Collections.EMPTY_LIST, ""));
-        assertEquals("", StringUtils.join(Collections.EMPTY_LIST, ","));
-
-        assertEquals("ab", StringUtils.join(Arrays.asList("a", "b"), ""));
-
-        assertEquals("a,b,c", StringUtils.join(Arrays.asList("a", "b", "c"), ","));
-    }
+/**
+ * Class that can be configured immediately after instantiation with a set of properties.
+ */
+public interface Configurable {
+    public void configure(Properties props);
 }

copycat-runtime/src/main/java/org/apache/kafka/copycat/util/ConnectorTaskId.java

@@ -0,0 +1,75 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.util;
+
+import java.io.Serializable;
+
+/**
+ * Unique ID for a single task. It includes a unique connector ID and a task ID that is unique within
+ * the connector.
+ */
+public class ConnectorTaskId implements Serializable {
+    private final String connector;
+    private final int task;
+
+    public ConnectorTaskId(String job, int task) {
+        this.connector = job;
+        this.task = task;
+    }
+
+    public String getConnector() {
+        return connector;
+    }
+
+    public int getTask() {
+        return task;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        ConnectorTaskId that = (ConnectorTaskId) o;
+
+        if (task != that.task) {
+            return false;
+        }
+        if (connector != null ? !connector.equals(that.connector) : that.connector != null) {
+            return false;
+        }
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = connector != null ? connector.hashCode() : 0;
+        result = 31 * result + task;
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return connector + '-' + task;
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/util/FutureCallback.java

@@ -0,0 +1,76 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.util;
+
+import java.util.concurrent.*;
+
+public class FutureCallback<T> implements Callback<T>, Future<T> {
+
+    private Callback underlying;
+    private CountDownLatch finishedLatch;
+    private T result = null;
+    private Throwable exception = null;
+
+    public FutureCallback(Callback underlying) {
+        this.underlying = underlying;
+        this.finishedLatch = new CountDownLatch(1);
+    }
+
+    @Override
+    public void onCompletion(Throwable error, T result) {
+        underlying.onCompletion(error, result);
+        this.exception = error;
+        this.result = result;
+        finishedLatch.countDown();
+    }
+
+    @Override
+    public boolean cancel(boolean b) {
+        return false;
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return false;
+    }
+
+    @Override
+    public boolean isDone() {
+        return finishedLatch.getCount() == 0;
+    }
+
+    @Override
+    public T get() throws InterruptedException, ExecutionException {
+        finishedLatch.await();
+        return getResult();
+    }
+
+    @Override
+    public T get(long l, TimeUnit timeUnit)
+            throws InterruptedException, ExecutionException, TimeoutException {
+        finishedLatch.await(l, timeUnit);
+        return getResult();
+    }
+
+    private T getResult() throws ExecutionException {
+        if (exception != null) {
+            throw new ExecutionException(exception);
+        }
+        return result;
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/util/KafkaUtils.java

@@ -0,0 +1,53 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.util;
+
+import kafka.utils.ZkUtils;
+import org.I0Itec.zkclient.ZkClient;
+import org.apache.kafka.copycat.connector.TopicPartition;
+import scala.collection.Seq;
+import scala.collection.mutable.Map;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import static scala.collection.JavaConversions.*;
+
+/**
+ * Some utilities for working with Kafka that aren't included with Kafka itself.
+ */
+public class KafkaUtils {
+
+    public static List<TopicPartition> getTopicPartitions(ZkClient zkClient, String... topics) {
+        return getTopicPartitions(zkClient, Arrays.asList(topics));
+    }
+
+    public static List<TopicPartition> getTopicPartitions(ZkClient zkClient, List<String> topics) {
+        Seq<String> scalaTopics = asScalaIterable(topics).toSeq();
+        List<TopicPartition> result = new ArrayList<TopicPartition>();
+        Map<String, Seq<Object>> partitionsByTopic
+                = ZkUtils.getPartitionsForTopics(zkClient, scalaTopics);
+        for (java.util.Map.Entry<String, Seq<Object>> entry : asJavaMap(partitionsByTopic).entrySet()) {
+            for (Object partition : asJavaIterable(entry.getValue())) {
+                result.add(new TopicPartition(entry.getKey(), (Integer) partition));
+            }
+        }
+        return result;
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/util/Reflection.java

@@ -0,0 +1,75 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.util;
+
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.lang.reflect.InvocationTargetException;
+import java.util.Properties;
+
+public class Reflection {
+    private static final Logger log = LoggerFactory.getLogger(Reflection.class);
+
+    /**
+     * Instantiate the class, which is a subclass of the specified type.
+     * @param className fully qualified name of the class to instantiate
+     * @param superType required supertype of the class
+     * @param <T>
+     * @return a new instance of the class instantiated with the default constructor
+     */
+    public static <T> T instantiate(String className, Class<T> superType) {
+        try {
+            Class<? extends T> taskClass = Class.forName(className).asSubclass(superType);
+            return taskClass.getConstructor().newInstance();
+        } catch (ClassNotFoundException e) {
+            log.error("Class not found: " + className, e);
+            throw new CopycatRuntimeException(e);
+        } catch (ClassCastException e) {
+            log.error("Specified class " + className + " is not a subclass of " + superType + ":", e);
+            throw new CopycatRuntimeException(e);
+        } catch (NoSuchMethodException e) {
+            log.error("Class does not have a default constructor: " + className, e);
+            throw new CopycatRuntimeException(e);
+        } catch (InstantiationException e) {
+            log.error("Class couldn't be instantiated: " + className, e);
+            throw new CopycatRuntimeException(e);
+        } catch (InvocationTargetException e) {
+            log.error("Class constructor threw an exception: " + className, e);
+            throw new CopycatRuntimeException(e);
+        } catch (IllegalAccessException e) {
+            log.error("Class couldn't be instantiated due to IllegalAccessException: " + className, e);
+            throw new CopycatRuntimeException(e);
+        }
+    }
+
+    /**
+     * Instantiate the class, which is a subclass of the specified type, and start it.
+     * @param className fully qualified name of the class to instantiate
+     * @param superType required supertype of the class
+     * @param <T>
+     * @return a new instance of the class instantiated with the default constructor
+     */
+    public static <T extends Configurable> T instantiateConfigurable(
+            String className, Class<T> superType, Properties props) {
+        T result = instantiate(className, superType);
+        result.configure(props);
+        return result;
+    }
+}

copycat-runtime/src/main/java/org/apache/kafka/copycat/util/ShutdownableThread.java

@@ -0,0 +1,150 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.util;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * <p>
+ * Thread class with support for triggering graceful and forcible shutdown. In graceful shutdown,
+ * a flag is set, which the thread should detect and try to exit gracefully from. In forcible
+ * shutdown, the thread is interrupted. These can be combined to give a thread a chance to exit
+ * gracefully, but then force it to exit if it takes too long.
+ * </p>
+ * <p>
+ * Implementations should override the {@link #execute} method and check {@link #getRunning} to
+ * determine whether they should try to gracefully exit.
+ * </p>
+ */
+public abstract class ShutdownableThread extends Thread {
+    private static final Logger log = LoggerFactory.getLogger(ShutdownableThread.class);
+
+    private AtomicBoolean isRunning = new AtomicBoolean(true);
+    private CountDownLatch shutdownLatch = new CountDownLatch(1);
+
+    /**
+     * An UncaughtExceptionHandler to register on every instance of this class. This is useful for
+     * testing, where AssertionExceptions in the thread may not cause the test to fail. Since one
+     * instance is used for all threads, it must be thread-safe.
+     */
+    volatile public static UncaughtExceptionHandler funcaughtExceptionHandler = null;
+
+    public ShutdownableThread(String name) {
+        // The default is daemon=true so that these threads will not prevent shutdown. We use this
+        // default because threads that are running user code that may not clean up properly, even
+        // when we attempt to forcibly shut them down.
+        this(name, true);
+    }
+
+    public ShutdownableThread(String name, boolean daemon) {
+        super(name);
+        this.setDaemon(daemon);
+        if (funcaughtExceptionHandler != null) {
+            this.setUncaughtExceptionHandler(funcaughtExceptionHandler);
+        }
+    }
+
+    /**
+     * Implementations should override this method with the main body for the thread.
+     */
+    public abstract void execute();
+
+    /**
+     * Returns true if the thread hasn't exited yet and none of the shutdown methods have been
+     * invoked
+     */
+    public boolean getRunning() {
+        return isRunning.get();
+    }
+
+    @Override
+    public void run() {
+        try {
+            execute();
+        } catch (Error e) {
+            log.error("Thread {} exiting with uncaught exception: ", getName(), e);
+            throw e;
+        } catch (RuntimeException e) {
+            log.error("Thread {} exiting with uncaught exception: ", getName(), e);
+            throw e;
+        } finally {
+            shutdownLatch.countDown();
+        }
+    }
+
+    /**
+     * Shutdown the thread, first trying to shut down gracefully using the specified timeout, then
+     * forcibly interrupting the thread.
+     * @param gracefulTimeout the maximum time to wait for a graceful exit
+     * @param unit the time unit of the timeout argument
+     */
+    public void shutdown(long gracefulTimeout, TimeUnit unit)
+            throws InterruptedException {
+        boolean success = gracefulShutdown(gracefulTimeout, unit);
+        if (!success) {
+            forceShutdown();
+        }
+    }
+
+    /**
+     * Attempt graceful shutdown
+     * @param timeout the maximum time to wait
+     * @param unit the time unit of the timeout argument
+     * @return true if successful, false if the timeout elapsed
+     */
+    public boolean gracefulShutdown(long timeout, TimeUnit unit) throws InterruptedException {
+        startGracefulShutdown();
+        return awaitShutdown(timeout, unit);
+    }
+
+    /**
+     * Start shutting down this thread gracefully, but do not block waiting for it to exit.
+     */
+    public void startGracefulShutdown() {
+        log.info("Starting graceful shutdown of thread {}", getName());
+        isRunning.set(false);
+    }
+
+    /**
+     * Awaits shutdown of this thread, waiting up to the timeout.
+     * @param timeout the maximum time to wait
+     * @param unit the time unit of the timeout argument
+     * @return true if successful, false if the timeout elapsed
+     * @throws InterruptedException
+     */
+    public boolean awaitShutdown(long timeout, TimeUnit unit) throws InterruptedException {
+        return shutdownLatch.await(timeout, unit);
+    }
+
+    /**
+     * Immediately tries to force the thread to shut down by interrupting it. This does not try to
+     * wait for the thread to truly exit because forcible shutdown is not always possible. By
+     * default, threads are marked as daemon threads so they will not prevent the process from
+     * exiting.
+     */
+    public void forceShutdown() throws InterruptedException {
+        log.info("Forcing shutdown of thread {}", getName());
+        isRunning.set(false);
+        interrupt();
+    }
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/runtime/WorkerSinkTaskTest.java

@@ -0,0 +1,421 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.common.utils.Time;
+import org.apache.kafka.clients.consumer.*;
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.copycat.cli.WorkerConfig;
+import org.apache.kafka.copycat.data.GenericRecord;
+import org.apache.kafka.copycat.data.GenericRecordBuilder;
+import org.apache.kafka.copycat.data.Schema;
+import org.apache.kafka.copycat.data.SchemaBuilder;
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.apache.kafka.copycat.sink.SinkRecord;
+import org.apache.kafka.copycat.sink.SinkTask;
+import org.apache.kafka.copycat.sink.SinkTaskContext;
+import org.apache.kafka.copycat.storage.Converter;
+import org.apache.kafka.copycat.util.ConnectorTaskId;
+import org.apache.kafka.copycat.util.MockTime;
+import org.apache.kafka.copycat.util.ThreadedTest;
+import org.easymock.*;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.powermock.api.easymock.PowerMock;
+import org.powermock.core.classloader.annotations.PowerMockIgnore;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.PowerMockRunner;
+import org.powermock.reflect.Whitebox;
+
+import java.util.*;
+
+import static org.junit.Assert.assertEquals;
+
+@RunWith(PowerMockRunner.class)
+@PrepareForTest(WorkerSinkTask.class)
+@PowerMockIgnore("javax.management.*")
+public class WorkerSinkTaskTest extends ThreadedTest {
+
+    // These are fixed to keep this code simpler
+    private static final String TOPIC = "test";
+    private static final int PARTITION = 12;
+    private static final long FIRST_OFFSET = 45;
+    private static final String KEY = "KEY";
+    private static final String VALUE = "VALUE";
+    private static final String TOPIC_PARTITION_STR = "test-12";
+
+    private static final TopicPartition TOPIC_PARTITION = new TopicPartition(TOPIC, PARTITION);
+    private static final org.apache.kafka.copycat.connector.TopicPartition TOPIC_PARTITION_COPYCAT =
+            new org.apache.kafka.copycat.connector.TopicPartition(TOPIC, PARTITION);
+
+    private ConnectorTaskId taskId = new ConnectorTaskId("job", 0);
+    private Time time;
+    private SinkTask sinkTask;
+    private WorkerConfig workerConfig;
+    private Converter converter;
+    private WorkerSinkTask workerTask;
+    private KafkaConsumer<Object, Object> consumer;
+    private WorkerSinkTaskThread workerThread;
+
+    private long recordsReturned;
+
+    @Override
+    public void setup() {
+        super.setup();
+        time = new MockTime();
+        sinkTask = PowerMock.createMock(SinkTask.class);
+        workerConfig = new WorkerConfig();
+        converter = PowerMock.createMock(Converter.class);
+        workerTask = PowerMock.createPartialMock(
+                WorkerSinkTask.class, new String[]{"createConsumer", "createWorkerThread"},
+                taskId, sinkTask, workerConfig, converter, time);
+
+        recordsReturned = 0;
+    }
+
+    @Test
+    public void testGetInputTopicPartitions() throws Exception {
+        Properties props = new Properties();
+        props.setProperty(SinkTask.TOPICPARTITIONS_CONFIG, "topic-1,foo-2");
+        assertEquals(
+                Arrays.asList(new org.apache.kafka.copycat.connector.TopicPartition("topic", 1),
+                        new org.apache.kafka.copycat.connector.TopicPartition("foo", 2)),
+                Whitebox.invokeMethod(workerTask, "getInputTopicPartitions", props)
+        );
+    }
+
+    @Test
+    public void testPollsInBackground() throws Exception {
+        Properties taskProps = new Properties();
+        taskProps.setProperty(SinkTask.TOPICPARTITIONS_CONFIG, TOPIC_PARTITION_STR);
+
+        expectInitializeTask(taskProps);
+        Capture<Collection<SinkRecord>> capturedRecords = expectPolls(1L);
+        expectStopTask(10L);
+
+        PowerMock.replayAll();
+
+        workerTask.start(taskProps);
+        for (int i = 0; i < 10; i++) {
+            workerThread.iteration();
+        }
+        workerTask.stop();
+        // No need for awaitStop since the thread is mocked
+        workerTask.close();
+
+        // Verify contents match expected values, i.e. that they were translated properly. With max
+        // batch size 1 and poll returns 1 message at a time, we should have a matching # of batches
+        assertEquals(10, capturedRecords.getValues().size());
+        int offset = 0;
+        for (Collection<SinkRecord> recs : capturedRecords.getValues()) {
+            assertEquals(1, recs.size());
+            for (SinkRecord rec : recs) {
+                SinkRecord referenceSinkRecord
+                        = new SinkRecord(TOPIC, PARTITION, KEY, VALUE, FIRST_OFFSET + offset);
+                assertEquals(referenceSinkRecord, rec);
+                offset++;
+            }
+        }
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testDeliverConvertsData() throws Exception {
+        // Validate conversion is performed when data is delivered
+        Schema schema = SchemaBuilder.record("sample").fields().endRecord();
+        GenericRecord record = new GenericRecordBuilder(schema).build();
+        byte[] rawKey = "key".getBytes(), rawValue = "value".getBytes();
+
+        ConsumerRecords<Object, Object> records = new ConsumerRecords<Object, Object>(
+                Collections.singletonMap(
+                        new TopicPartition("topic", 0),
+                        Collections.singletonList(
+                                new ConsumerRecord<Object, Object>("topic", 0, 0, rawKey, rawValue))));
+
+        // Exact data doesn't matter, but should be passed directly to sink task
+        EasyMock.expect(converter.toCopycatData(rawKey))
+                .andReturn(record);
+        EasyMock.expect(converter.toCopycatData(rawValue))
+                .andReturn(record);
+        Capture<Collection<SinkRecord>> capturedRecords
+                = EasyMock.newCapture(CaptureType.ALL);
+        sinkTask.put(EasyMock.capture(capturedRecords));
+        EasyMock.expectLastCall();
+
+        PowerMock.replayAll();
+
+        Whitebox.invokeMethod(workerTask, "deliverMessages", records);
+        assertEquals(record, capturedRecords.getValue().iterator().next().getKey());
+        assertEquals(record, capturedRecords.getValue().iterator().next().getValue());
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testCommit() throws Exception {
+        Properties taskProps = new Properties();
+        taskProps.setProperty(SinkTask.TOPICPARTITIONS_CONFIG, TOPIC_PARTITION_STR);
+
+        expectInitializeTask(taskProps);
+        // Make each poll() take the offset commit interval
+        Capture<Collection<SinkRecord>> capturedRecords
+                = expectPolls(WorkerConfig.OFFSET_COMMIT_INTERVAL_MS_DEFAULT);
+        expectOffsetFlush(1L, null, null, 0, true);
+        expectStopTask(2);
+
+        PowerMock.replayAll();
+
+        workerTask.start(taskProps);
+        // First iteration gets one record
+        workerThread.iteration();
+        // Second triggers commit, gets a second offset
+        workerThread.iteration();
+        // Commit finishes synchronously for testing so we can check this immediately
+        assertEquals(0, workerThread.getCommitFailures());
+        workerTask.stop();
+        workerTask.close();
+
+        assertEquals(2, capturedRecords.getValues().size());
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testCommitTaskFlushFailure() throws Exception {
+        Properties taskProps = new Properties();
+        taskProps.setProperty(SinkTask.TOPICPARTITIONS_CONFIG, TOPIC_PARTITION_STR);
+
+        expectInitializeTask(taskProps);
+        Capture<Collection<SinkRecord>> capturedRecords
+                = expectPolls(WorkerConfig.OFFSET_COMMIT_INTERVAL_MS_DEFAULT);
+        expectOffsetFlush(1L, new RuntimeException(), null, 0, true);
+        expectStopTask(2);
+
+        PowerMock.replayAll();
+
+        workerTask.start(taskProps);
+        // Second iteration triggers commit
+        workerThread.iteration();
+        workerThread.iteration();
+        assertEquals(1, workerThread.getCommitFailures());
+        assertEquals(false, Whitebox.getInternalState(workerThread, "committing"));
+        workerTask.stop();
+        workerTask.close();
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testCommitConsumerFailure() throws Exception {
+        Properties taskProps = new Properties();
+        taskProps.setProperty(SinkTask.TOPICPARTITIONS_CONFIG, TOPIC_PARTITION_STR);
+
+        expectInitializeTask(taskProps);
+        Capture<Collection<SinkRecord>> capturedRecords
+                = expectPolls(WorkerConfig.OFFSET_COMMIT_INTERVAL_MS_DEFAULT);
+        expectOffsetFlush(1L, null, new Exception(), 0, true);
+        expectStopTask(2);
+
+        PowerMock.replayAll();
+
+        workerTask.start(taskProps);
+        // Second iteration triggers commit
+        workerThread.iteration();
+        workerThread.iteration();
+        // TODO Response to consistent failures?
+        assertEquals(1, workerThread.getCommitFailures());
+        assertEquals(false, Whitebox.getInternalState(workerThread, "committing"));
+        workerTask.stop();
+        workerTask.close();
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testCommitTimeout() throws Exception {
+        Properties taskProps = new Properties();
+        taskProps.setProperty(SinkTask.TOPICPARTITIONS_CONFIG, TOPIC_PARTITION_STR);
+
+        expectInitializeTask(taskProps);
+        // Cut down amount of time to pass in each poll so we trigger exactly 1 offset commit
+        Capture<Collection<SinkRecord>> capturedRecords
+                = expectPolls(WorkerConfig.OFFSET_COMMIT_INTERVAL_MS_DEFAULT / 2);
+        expectOffsetFlush(2L, null, null, WorkerConfig.OFFSET_COMMIT_TIMEOUT_MS_DEFAULT, false);
+        expectStopTask(4);
+
+        PowerMock.replayAll();
+
+        workerTask.start(taskProps);
+        // Third iteration triggers commit, fourth gives a chance to trigger the timeout but doesn't
+        // trigger another commit
+        workerThread.iteration();
+        workerThread.iteration();
+        workerThread.iteration();
+        workerThread.iteration();
+        // TODO Response to consistent failures?
+        assertEquals(1, workerThread.getCommitFailures());
+        assertEquals(false, Whitebox.getInternalState(workerThread, "committing"));
+        workerTask.stop();
+        workerTask.close();
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testGetInputPartitionsSingle() throws Exception {
+        Properties taskProps = new Properties();
+        taskProps.setProperty(SinkTask.TOPICPARTITIONS_CONFIG, "test-1");
+
+        assertEquals(Arrays.asList(new org.apache.kafka.copycat.connector.TopicPartition("test", 1)),
+                Whitebox.invokeMethod(workerTask, "getInputTopicPartitions", taskProps));
+    }
+
+    @Test
+    public void testGetInputPartitionsList() throws Exception {
+        Properties taskProps = new Properties();
+        taskProps.setProperty(SinkTask.TOPICPARTITIONS_CONFIG, "test-1,foo-2,bar-3");
+
+        assertEquals(Arrays.asList(
+                        new org.apache.kafka.copycat.connector.TopicPartition("test", 1),
+                        new org.apache.kafka.copycat.connector.TopicPartition("foo", 2),
+                        new org.apache.kafka.copycat.connector.TopicPartition("bar", 3)),
+                Whitebox.invokeMethod(workerTask, "getInputTopicPartitions", taskProps));
+    }
+
+    @Test(expected = CopycatRuntimeException.class)
+    public void testGetInputPartitionsMissing() throws Exception {
+        // Missing setting
+        Whitebox.invokeMethod(workerTask, "getInputTopicPartitions", new Properties());
+    }
+
+
+    private KafkaConsumer<Object, Object> expectInitializeTask(Properties taskProps)
+            throws Exception {
+        sinkTask.initialize(EasyMock.anyObject(SinkTaskContext.class));
+        PowerMock.expectLastCall();
+        sinkTask.start(taskProps);
+        PowerMock.expectLastCall();
+
+        consumer = PowerMock.createMock(KafkaConsumer.class);
+        PowerMock.expectPrivate(workerTask, "createConsumer", taskProps)
+                .andReturn(consumer);
+        workerThread = PowerMock.createPartialMock(WorkerSinkTaskThread.class, new String[]{"start"},
+                workerTask, "mock-worker-thread", time,
+                workerConfig);
+        PowerMock.expectPrivate(workerTask, "createWorkerThread")
+                .andReturn(workerThread);
+        workerThread.start();
+        PowerMock.expectLastCall();
+        return consumer;
+    }
+
+    private void expectStopTask(final long expectedMessages) throws Exception {
+        final long finalOffset = FIRST_OFFSET + expectedMessages - 1;
+
+        sinkTask.stop();
+        PowerMock.expectLastCall();
+
+        // Triggers final offset commit
+        EasyMock.expect(consumer.subscriptions()).andReturn(Collections.singleton(TOPIC_PARTITION));
+        EasyMock.expect(consumer.position(TOPIC_PARTITION)).andAnswer(new IAnswer<Long>() {
+            @Override
+            public Long answer() throws Throwable {
+                return FIRST_OFFSET + recordsReturned - 1;
+            }
+        });
+        final Capture<ConsumerCommitCallback> capturedCallback = EasyMock.newCapture();
+        consumer.commit(EasyMock.eq(Collections.singletonMap(TOPIC_PARTITION, finalOffset)),
+                EasyMock.eq(CommitType.SYNC),
+                EasyMock.capture(capturedCallback));
+
+        consumer.close();
+        PowerMock.expectLastCall();
+    }
+
+    // Note that this can only be called once per test currently
+    private Capture<Collection<SinkRecord>> expectPolls(final long pollDelayMs) throws Exception {
+        // Stub out all the consumer stream/iterator responses, which we just want to verify occur,
+        // but don't care about the exact details here.
+        EasyMock.expect(consumer.poll(EasyMock.anyLong())).andStubAnswer(
+                new IAnswer<ConsumerRecords<Object, Object>>() {
+                    @Override
+                    public ConsumerRecords<Object, Object> answer() throws Throwable {
+                        // "Sleep" so time will progress
+                        time.sleep(pollDelayMs);
+                        ConsumerRecords<Object, Object> records = new ConsumerRecords<Object, Object>(
+                                Collections.singletonMap(new TopicPartition(TOPIC, PARTITION), Arrays.asList(
+                                        new ConsumerRecord<Object, Object>(TOPIC, PARTITION,
+                                                FIRST_OFFSET + recordsReturned, KEY,
+                                                VALUE))));
+                        recordsReturned++;
+                        return records;
+                    }
+                });
+        EasyMock.expect(converter.toCopycatData(KEY)).andReturn(KEY).anyTimes();
+        EasyMock.expect(converter.toCopycatData(VALUE)).andReturn(VALUE).anyTimes();
+        Capture<Collection<SinkRecord>> capturedRecords = EasyMock.newCapture(CaptureType.ALL);
+        sinkTask.put(EasyMock.capture(capturedRecords));
+        EasyMock.expectLastCall().anyTimes();
+        return capturedRecords;
+    }
+
+    private Capture<ConsumerCommitCallback> expectOffsetFlush(final long expectedMessages,
+                                                              final RuntimeException flushError,
+                                                              final Exception consumerCommitError,
+                                                              final long consumerCommitDelayMs,
+                                                              final boolean invokeCallback)
+            throws Exception {
+        final long finalOffset = FIRST_OFFSET + expectedMessages - 1;
+
+        EasyMock.expect(consumer.subscriptions()).andReturn(Collections.singleton(TOPIC_PARTITION));
+        EasyMock.expect(consumer.position(TOPIC_PARTITION)).andAnswer(
+                new IAnswer<Long>() {
+                    @Override
+                    public Long answer() throws Throwable {
+                        return FIRST_OFFSET + recordsReturned - 1;
+                    }
+                }
+        );
+
+        sinkTask.flush(Collections.singletonMap(TOPIC_PARTITION_COPYCAT, finalOffset));
+        IExpectationSetters<Object> flushExpectation = PowerMock.expectLastCall();
+        if (flushError != null) {
+            flushExpectation.andThrow(flushError).once();
+            return null;
+        }
+
+        final Capture<ConsumerCommitCallback> capturedCallback = EasyMock.newCapture();
+        final Map<TopicPartition, Long> offsets = Collections.singletonMap(TOPIC_PARTITION, finalOffset);
+        consumer.commit(EasyMock.eq(offsets),
+                EasyMock.eq(CommitType.ASYNC),
+                EasyMock.capture(capturedCallback));
+        PowerMock.expectLastCall().andAnswer(new IAnswer<Object>() {
+            @Override
+            public Object answer() throws Throwable {
+                time.sleep(consumerCommitDelayMs);
+                if (invokeCallback) {
+                    capturedCallback.getValue().onComplete(offsets, consumerCommitError);
+                }
+                return null;
+            }
+        });
+        return capturedCallback;
+    }
+
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/runtime/WorkerSourceTaskTest.java

@@ -0,0 +1,275 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.common.utils.SystemTime;
+import org.apache.kafka.clients.producer.KafkaProducer;
+import org.apache.kafka.clients.producer.ProducerRecord;
+import org.apache.kafka.clients.producer.RecordMetadata;
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.copycat.cli.WorkerConfig;
+import org.apache.kafka.copycat.data.GenericRecord;
+import org.apache.kafka.copycat.data.GenericRecordBuilder;
+import org.apache.kafka.copycat.data.Schema;
+import org.apache.kafka.copycat.data.SchemaBuilder;
+import org.apache.kafka.copycat.source.SourceRecord;
+import org.apache.kafka.copycat.source.SourceTask;
+import org.apache.kafka.copycat.source.SourceTaskContext;
+import org.apache.kafka.copycat.storage.Converter;
+import org.apache.kafka.copycat.storage.OffsetStorageReader;
+import org.apache.kafka.copycat.storage.OffsetStorageWriter;
+import org.apache.kafka.copycat.util.Callback;
+import org.apache.kafka.copycat.util.ConnectorTaskId;
+import org.apache.kafka.copycat.util.ThreadedTest;
+import org.easymock.Capture;
+import org.easymock.EasyMock;
+import org.easymock.IAnswer;
+import org.easymock.IExpectationSetters;
+import org.junit.Test;
+import org.powermock.api.easymock.PowerMock;
+import org.powermock.reflect.Whitebox;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Properties;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+import static org.junit.Assert.*;
+
+public class WorkerSourceTaskTest extends ThreadedTest {
+    private static final byte[] STREAM_BYTES = "stream".getBytes();
+    private static final byte[] OFFSET_BYTES = "offset-1".getBytes();
+
+    private static final Schema RECORD_SCHEMA = SchemaBuilder.record("sample").fields().endRecord();
+    private static final GenericRecord RECORD = new GenericRecordBuilder(RECORD_SCHEMA).build();
+    // The actual format of this data doesn't matter -- we just want to see that the right version
+    // is used in the right place.
+    private static final String CONVERTED_RECORD = "converted-record";
+
+    private ConnectorTaskId taskId = new ConnectorTaskId("job", 0);
+    private WorkerConfig config = new WorkerConfig();
+    private SourceTask sourceTask;
+    private Converter converter;
+    private KafkaProducer<Object, Object> producer;
+    private OffsetStorageReader offsetReader;
+    private OffsetStorageWriter offsetWriter;
+    private WorkerSourceTask workerTask;
+    private Future<RecordMetadata> sendFuture;
+
+    private Capture<org.apache.kafka.clients.producer.Callback> producerCallbacks;
+
+    private static final Properties EMPTY_TASK_PROPS = new Properties();
+    private static final List<SourceRecord> RECORDS = Arrays.asList(
+            new SourceRecord(STREAM_BYTES, OFFSET_BYTES,
+                    "topic", RECORD)
+    );
+
+    @Override
+    public void setup() {
+        super.setup();
+        sourceTask = PowerMock.createMock(SourceTask.class);
+        converter = PowerMock.createMock(Converter.class);
+        producer = PowerMock.createMock(KafkaProducer.class);
+        offsetReader = PowerMock.createMock(OffsetStorageReader.class);
+        offsetWriter = PowerMock.createMock(OffsetStorageWriter.class);
+        sendFuture = PowerMock.createMock(Future.class);
+        producerCallbacks = EasyMock.newCapture();
+    }
+
+    private void createWorkerTask() {
+        workerTask = new WorkerSourceTask(taskId, sourceTask, converter, producer,
+                offsetReader, offsetWriter,
+                config, new SystemTime());
+    }
+
+    @Test
+    public void testPollsInBackground() throws Exception {
+        createWorkerTask();
+
+        sourceTask.initialize(EasyMock.anyObject(SourceTaskContext.class));
+        EasyMock.expectLastCall();
+        sourceTask.start(EMPTY_TASK_PROPS);
+        EasyMock.expectLastCall();
+
+        final CountDownLatch pollLatch = expectPolls(10);
+        // In this test, we don't flush, so nothing goes any further than the offset writer
+
+        sourceTask.stop();
+        EasyMock.expectLastCall();
+        expectOffsetFlush(true);
+
+        PowerMock.replayAll();
+
+        workerTask.start(EMPTY_TASK_PROPS);
+        awaitPolls(pollLatch);
+        workerTask.stop();
+        assertEquals(true, workerTask.awaitStop(1000));
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testCommit() throws Exception {
+        // Test that the task commits properly when prompted
+        createWorkerTask();
+
+        sourceTask.initialize(EasyMock.anyObject(SourceTaskContext.class));
+        EasyMock.expectLastCall();
+        sourceTask.start(EMPTY_TASK_PROPS);
+        EasyMock.expectLastCall();
+
+        // We'll wait for some data, then trigger a flush
+        final CountDownLatch pollLatch = expectPolls(1);
+        expectOffsetFlush(true);
+
+        sourceTask.stop();
+        EasyMock.expectLastCall();
+        expectOffsetFlush(true);
+
+        PowerMock.replayAll();
+
+        workerTask.start(EMPTY_TASK_PROPS);
+        awaitPolls(pollLatch);
+        assertTrue(workerTask.commitOffsets());
+        workerTask.stop();
+        assertEquals(true, workerTask.awaitStop(1000));
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testCommitFailure() throws Exception {
+        // Test that the task commits properly when prompted
+        createWorkerTask();
+
+        sourceTask.initialize(EasyMock.anyObject(SourceTaskContext.class));
+        EasyMock.expectLastCall();
+        sourceTask.start(EMPTY_TASK_PROPS);
+        EasyMock.expectLastCall();
+
+        // We'll wait for some data, then trigger a flush
+        final CountDownLatch pollLatch = expectPolls(1);
+        expectOffsetFlush(false);
+
+        sourceTask.stop();
+        EasyMock.expectLastCall();
+        expectOffsetFlush(true);
+
+        PowerMock.replayAll();
+
+        workerTask.start(EMPTY_TASK_PROPS);
+        awaitPolls(pollLatch);
+        assertFalse(workerTask.commitOffsets());
+        workerTask.stop();
+        assertEquals(true, workerTask.awaitStop(1000));
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testSendRecordsConvertsData() throws Exception {
+        createWorkerTask();
+
+        List<SourceRecord> records = new ArrayList<SourceRecord>();
+        // Can just use the same record for key and value
+        records.add(new SourceRecord(STREAM_BYTES, OFFSET_BYTES, "topic", null, RECORD, RECORD));
+
+        Capture<ProducerRecord> sent = expectSendRecord();
+
+        PowerMock.replayAll();
+
+        Whitebox.invokeMethod(workerTask, "sendRecords", records);
+        assertEquals(CONVERTED_RECORD, sent.getValue().key());
+        assertEquals(CONVERTED_RECORD, sent.getValue().value());
+
+        PowerMock.verifyAll();
+    }
+
+
+    private CountDownLatch expectPolls(int count) throws InterruptedException {
+        final CountDownLatch latch = new CountDownLatch(count);
+        // Note that we stub these to allow any number of calls because the thread will continue to
+        // run. The count passed in + latch returned just makes sure we get *at least* that number of
+        // calls
+        EasyMock.expect(sourceTask.poll())
+                .andStubAnswer(new IAnswer<List<SourceRecord>>() {
+                    @Override
+                    public List<SourceRecord> answer() throws Throwable {
+                        latch.countDown();
+                        return RECORDS;
+                    }
+                });
+        // Fallout of the poll() call
+        expectSendRecord();
+        return latch;
+    }
+
+    private Capture<ProducerRecord> expectSendRecord() throws InterruptedException {
+        EasyMock.expect(converter.fromCopycatData(null)).andStubReturn(null);
+        EasyMock.expect(converter.fromCopycatData(RECORD)).andStubReturn(CONVERTED_RECORD);
+
+        Capture<ProducerRecord> sent = EasyMock.newCapture();
+        // 1. Converted data passed to the producer, which will need callbacks invoked for flush to work
+        EasyMock.expect(
+                producer.send(EasyMock.capture(sent),
+                        EasyMock.capture(producerCallbacks)))
+                .andStubAnswer(new IAnswer<Future<RecordMetadata>>() {
+                    @Override
+                    public Future<RecordMetadata> answer() throws Throwable {
+                        synchronized (producerCallbacks) {
+                            for (org.apache.kafka.clients.producer.Callback cb : producerCallbacks.getValues()) {
+                                cb.onCompletion(new RecordMetadata(new TopicPartition("foo", 0), 0, 0), null);
+                            }
+                            producerCallbacks.reset();
+                        }
+                        return sendFuture;
+                    }
+                });
+        // 2. Offset data is passed to the offset storage.
+        offsetWriter.setOffset(STREAM_BYTES, OFFSET_BYTES);
+        PowerMock.expectLastCall().anyTimes();
+
+        return sent;
+    }
+
+    private void awaitPolls(CountDownLatch latch) throws InterruptedException {
+        latch.await(1000, TimeUnit.MILLISECONDS);
+    }
+
+    private void expectOffsetFlush(boolean succeed) throws Exception {
+        EasyMock.expect(offsetWriter.beginFlush()).andReturn(true);
+        Future<Void> flushFuture = PowerMock.createMock(Future.class);
+        EasyMock.expect(offsetWriter.doFlush(EasyMock.anyObject(Callback.class)))
+                .andReturn(flushFuture);
+        // Should throw for failure
+        IExpectationSetters<Void> futureGetExpect = EasyMock.expect(
+                flushFuture.get(EasyMock.anyLong(), EasyMock.anyObject(TimeUnit.class)));
+        if (succeed) {
+            futureGetExpect.andReturn(null);
+        } else {
+            futureGetExpect.andThrow(new TimeoutException());
+            offsetWriter.cancelFlush();
+            PowerMock.expectLastCall();
+        }
+    }
+
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/runtime/WorkerTest.java

@@ -0,0 +1,177 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime;
+
+import org.apache.kafka.common.utils.Time;
+import org.I0Itec.zkclient.ZkClient;
+import org.apache.kafka.clients.producer.KafkaProducer;
+import org.apache.kafka.copycat.cli.WorkerConfig;
+import org.apache.kafka.copycat.errors.CopycatException;
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.apache.kafka.copycat.source.SourceRecord;
+import org.apache.kafka.copycat.source.SourceTask;
+import org.apache.kafka.copycat.storage.*;
+import org.apache.kafka.copycat.util.ConnectorTaskId;
+import org.apache.kafka.copycat.util.MockTime;
+import org.apache.kafka.copycat.util.ThreadedTest;
+import org.easymock.EasyMock;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.powermock.api.easymock.PowerMock;
+import org.powermock.core.classloader.annotations.PowerMockIgnore;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.PowerMockRunner;
+
+import java.util.List;
+import java.util.Properties;
+
+@RunWith(PowerMockRunner.class)
+@PrepareForTest(Worker.class)
+@PowerMockIgnore("javax.management.*")
+public class WorkerTest extends ThreadedTest {
+
+    private ConnectorTaskId taskId = new ConnectorTaskId("job", 0);
+    private Worker worker;
+    private OffsetBackingStore offsetBackingStore = PowerMock.createMock(OffsetBackingStore.class);
+    private OffsetSerializer offsetKeySerializer = PowerMock.createMock(OffsetSerializer.class);
+    private OffsetSerializer offsetValueSerializer = PowerMock.createMock(OffsetSerializer.class);
+    private OffsetDeserializer offsetKeyDeserializer = PowerMock.createMock(OffsetDeserializer.class);
+    private OffsetDeserializer offsetValueDeserializer = PowerMock.createMock(OffsetDeserializer.class);
+
+    @Before
+    public void setup() {
+        super.setup();
+
+        // TODO: Remove schema registry URL
+        Properties workerProps = new Properties();
+        workerProps.setProperty("schema.registry.url", "http://localhost:8081");
+        WorkerConfig config = new WorkerConfig(workerProps);
+        ZkClient zkClient = PowerMock.createMock(ZkClient.class);
+        worker = new Worker(new MockTime(), config, offsetBackingStore,
+                offsetKeySerializer, offsetValueSerializer,
+                offsetKeyDeserializer, offsetValueDeserializer,
+                zkClient);
+        worker.start();
+    }
+
+    @Test
+    public void testAddRemoveTask() throws Exception {
+        ConnectorTaskId taskId = new ConnectorTaskId("job", 0);
+
+        // Create
+        TestSourceTask task = PowerMock.createMock(TestSourceTask.class);
+        WorkerSourceTask workerTask = PowerMock.createMock(WorkerSourceTask.class);
+
+        PowerMock.mockStatic(Worker.class);
+        PowerMock.expectPrivate(Worker.class, "instantiateTask", TestSourceTask.class.getName())
+                .andReturn(task);
+
+        PowerMock.expectNew(
+                WorkerSourceTask.class, EasyMock.eq(taskId), EasyMock.eq(task),
+                EasyMock.anyObject(Converter.class),
+                EasyMock.anyObject(KafkaProducer.class),
+                EasyMock.anyObject(OffsetStorageReader.class),
+                EasyMock.anyObject(OffsetStorageWriter.class),
+                EasyMock.anyObject(WorkerConfig.class),
+                EasyMock.anyObject(Time.class))
+                .andReturn(workerTask);
+        Properties origProps = new Properties();
+        workerTask.start(origProps);
+        EasyMock.expectLastCall();
+
+        // Remove
+        workerTask.stop();
+        EasyMock.expectLastCall();
+        EasyMock.expect(workerTask.awaitStop(EasyMock.anyLong())).andStubReturn(true);
+        workerTask.close();
+        EasyMock.expectLastCall();
+
+        PowerMock.replayAll();
+
+        worker.addTask(taskId, TestSourceTask.class.getName(), origProps);
+        worker.stopTask(taskId);
+        // Nothing should be left, so this should effectively be a nop
+        worker.stop();
+
+        PowerMock.verifyAll();
+    }
+
+    @Test(expected = CopycatRuntimeException.class)
+    public void testStopInvalidTask() throws CopycatException {
+        worker.stopTask(taskId);
+    }
+
+    @Test
+    public void testCleanupTasksOnStop() throws Exception {
+        // Create
+        TestSourceTask task = PowerMock.createMock(TestSourceTask.class);
+        WorkerSourceTask workerTask = PowerMock.createMock(WorkerSourceTask.class);
+
+        PowerMock.mockStatic(Worker.class);
+        PowerMock.expectPrivate(Worker.class, "instantiateTask", TestSourceTask.class.getName())
+                .andReturn(task);
+
+        PowerMock.expectNew(
+                WorkerSourceTask.class, EasyMock.eq(taskId), EasyMock.eq(task),
+                EasyMock.anyObject(Converter.class),
+                EasyMock.anyObject(KafkaProducer.class),
+                EasyMock.anyObject(OffsetStorageReader.class),
+                EasyMock.anyObject(OffsetStorageWriter.class),
+                EasyMock.anyObject(WorkerConfig.class),
+                EasyMock.anyObject(Time.class))
+                .andReturn(workerTask);
+        Properties origProps = new Properties();
+        workerTask.start(origProps);
+        EasyMock.expectLastCall();
+
+        // Remove on Worker.stop()
+        workerTask.stop();
+        EasyMock.expectLastCall();
+        EasyMock.expect(workerTask.awaitStop(EasyMock.anyLong())).andReturn(true);
+        // Note that in this case we *do not* commit offsets since it's an unclean shutdown
+        workerTask.close();
+        EasyMock.expectLastCall();
+
+        PowerMock.replayAll();
+
+        worker.addTask(taskId, TestSourceTask.class.getName(), origProps);
+        worker.stop();
+
+        PowerMock.verifyAll();
+    }
+
+
+    private static class TestSourceTask extends SourceTask<Object, Object> {
+        public TestSourceTask() {
+        }
+
+        @Override
+        public void start(Properties props) {
+        }
+
+        @Override
+        public List<SourceRecord> poll() throws InterruptedException {
+            return null;
+        }
+
+        @Override
+        public void stop() throws CopycatException {
+        }
+    }
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/runtime/standalone/StandaloneCoordinatorRestoreTest.java

@@ -0,0 +1,94 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime.standalone;
+
+import org.apache.kafka.copycat.runtime.ConnectorConfig;
+import org.apache.kafka.copycat.runtime.Worker;
+import org.apache.kafka.copycat.sink.SinkConnector;
+import org.apache.kafka.copycat.util.Callback;
+import org.apache.kafka.copycat.util.KafkaUtils;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.powermock.api.easymock.PowerMock;
+import org.powermock.core.classloader.annotations.PowerMockIgnore;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.PowerMockRunner;
+
+import java.io.File;
+import java.util.Properties;
+
+@RunWith(PowerMockRunner.class)
+@PrepareForTest({StandaloneCoordinator.class, KafkaUtils.class})
+@PowerMockIgnore("javax.management.*")
+public class StandaloneCoordinatorRestoreTest extends StandaloneCoordinatorTestBase {
+    private File coordinatorConfigFile;
+
+    @Before
+    public void setup() throws Exception {
+        worker = PowerMock.createMock(Worker.class);
+        Properties coordinatorProps = new Properties();
+        coordinatorProps.setProperty(StandaloneCoordinator.STORAGE_CONFIG,
+                FileConfigStorage.class.getName());
+        coordinatorConfigFile = File.createTempFile("test-coordinator-config", null);
+        coordinatorConfigFile.delete(); // Delete since we just needed a random file path
+        coordinatorProps.setProperty(FileConfigStorage.FILE_CONFIG,
+                coordinatorConfigFile.getAbsolutePath());
+        coordinator = new StandaloneCoordinator(worker, coordinatorProps);
+        createCallback = PowerMock.createMock(Callback.class);
+
+        connectorProps = new Properties();
+        connectorProps.setProperty(ConnectorConfig.NAME_CONFIG, CONNECTOR_NAME);
+        connectorProps.setProperty(SinkConnector.TOPICS_CONFIG, TOPICS_LIST_STR);
+        PowerMock.mockStatic(StandaloneCoordinator.class);
+        PowerMock.mockStatic(KafkaUtils.class);
+
+        // These can be anything since connectors can pass along whatever they want.
+        taskProps = new Properties();
+        taskProps.setProperty("foo", "bar");
+    }
+
+    @After
+    public void tearDown() {
+        coordinatorConfigFile.delete();
+    }
+
+    @Test
+    public void testRestoreConnectors() throws Exception {
+        connector = PowerMock.createMock(BogusSourceClass.class);
+        expectAdd(BogusSourceClass.class, BogusSourceTask.class, false);
+        expectStop();
+        // Restarting should recreate the same connector
+        expectRestore(BogusSourceClass.class, BogusSourceTask.class);
+        expectStop();
+
+        PowerMock.replayAll();
+
+        // One run to seed the config storage with the job
+        coordinator.start();
+        coordinator.addConnector(connectorProps, createCallback);
+        coordinator.stop();
+
+        // Second run should restore the connector
+        coordinator.start();
+        coordinator.stop();
+
+        PowerMock.verifyAll();
+    }
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/runtime/standalone/StandaloneCoordinatorTest.java

@@ -0,0 +1,100 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime.standalone;
+
+import org.apache.kafka.copycat.runtime.ConnectorConfig;
+import org.apache.kafka.copycat.runtime.Worker;
+import org.apache.kafka.copycat.sink.SinkConnector;
+import org.apache.kafka.copycat.util.Callback;
+import org.apache.kafka.copycat.util.FutureCallback;
+import org.apache.kafka.copycat.util.KafkaUtils;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.powermock.api.easymock.PowerMock;
+import org.powermock.core.classloader.annotations.PowerMockIgnore;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.PowerMockRunner;
+
+import java.util.Properties;
+import java.util.concurrent.TimeUnit;
+
+@RunWith(PowerMockRunner.class)
+@PrepareForTest({StandaloneCoordinator.class, KafkaUtils.class})
+@PowerMockIgnore("javax.management.*")
+public class StandaloneCoordinatorTest extends StandaloneCoordinatorTestBase {
+
+    @Before
+    public void setup() {
+        worker = PowerMock.createMock(Worker.class);
+        coordinator = new StandaloneCoordinator(worker, new Properties());
+        createCallback = PowerMock.createMock(Callback.class);
+
+        connectorProps = new Properties();
+        connectorProps.setProperty(ConnectorConfig.NAME_CONFIG, CONNECTOR_NAME);
+        connectorProps.setProperty(SinkConnector.TOPICS_CONFIG, TOPICS_LIST_STR);
+        PowerMock.mockStatic(StandaloneCoordinator.class);
+        PowerMock.mockStatic(KafkaUtils.class);
+
+        // These can be anything since connectors can pass along whatever they want.
+        taskProps = new Properties();
+        taskProps.setProperty("foo", "bar");
+    }
+
+    @Test
+    public void testCreateSourceConnector() throws Exception {
+        connector = PowerMock.createMock(BogusSourceClass.class);
+        expectAdd(BogusSourceClass.class, BogusSourceTask.class, false);
+        PowerMock.replayAll();
+
+        coordinator.addConnector(connectorProps, createCallback);
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testCreateSinkConnector() throws Exception {
+        connector = PowerMock.createMock(BogusSinkClass.class);
+        expectAdd(BogusSinkClass.class, BogusSinkTask.class, true);
+
+        PowerMock.replayAll();
+
+        coordinator.addConnector(connectorProps, createCallback);
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testDestroyConnector() throws Exception {
+        connector = PowerMock.createMock(BogusSourceClass.class);
+        expectAdd(BogusSourceClass.class, BogusSourceTask.class, false);
+        expectDestroy();
+        PowerMock.replayAll();
+
+        coordinator.addConnector(connectorProps, createCallback);
+        FutureCallback<Void> futureCb = new FutureCallback<Void>(new Callback() {
+            @Override
+            public void onCompletion(Throwable error, Object result) {
+
+            }
+        });
+        coordinator.deleteConnector(CONNECTOR_NAME, futureCb);
+        futureCb.get(1000L, TimeUnit.MILLISECONDS);
+        PowerMock.verifyAll();
+    }
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/runtime/standalone/StandaloneCoordinatorTestBase.java

@@ -0,0 +1,133 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.runtime.standalone;
+
+import org.I0Itec.zkclient.ZkClient;
+import org.apache.kafka.copycat.connector.Connector;
+import org.apache.kafka.copycat.connector.Task;
+import org.apache.kafka.copycat.connector.TopicPartition;
+import org.apache.kafka.copycat.errors.CopycatException;
+import org.apache.kafka.copycat.runtime.ConnectorConfig;
+import org.apache.kafka.copycat.runtime.Worker;
+import org.apache.kafka.copycat.sink.SinkConnector;
+import org.apache.kafka.copycat.sink.SinkTask;
+import org.apache.kafka.copycat.source.SourceConnector;
+import org.apache.kafka.copycat.source.SourceTask;
+import org.apache.kafka.copycat.util.Callback;
+import org.apache.kafka.copycat.util.ConnectorTaskId;
+import org.apache.kafka.copycat.util.KafkaUtils;
+import org.easymock.EasyMock;
+import org.powermock.api.easymock.PowerMock;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Properties;
+
+public class StandaloneCoordinatorTestBase {
+
+    protected static final String CONNECTOR_NAME = "test";
+    protected static final String TOPICS_LIST_STR = "topic1,topic2";
+    protected static final List<String> TOPICS_LIST = Arrays.asList("topic1", "topic2");
+    protected static final List<TopicPartition> TOPIC_PARTITIONS = Arrays.asList(
+            new TopicPartition("topic1", 1), new TopicPartition("topic2", 1));
+    protected static final String TOPIC_PARTITIONS_STR = "topic1-1,topic2-1";
+
+    protected StandaloneCoordinator coordinator;
+    protected Worker worker;
+    protected Connector connector;
+    protected Callback<String> createCallback;
+
+    protected Properties connectorProps;
+    protected Properties taskProps;
+
+    protected void expectAdd(Class<? extends Connector> connClass,
+                             Class<? extends Task> taskClass,
+                             boolean sink) throws Exception {
+        expectCreate(connClass, taskClass, sink, true);
+    }
+
+    protected void expectRestore(Class<? extends Connector> connClass,
+                                 Class<? extends Task> taskClass) throws Exception {
+        // Restore never uses a callback. These tests always use sources
+        expectCreate(connClass, taskClass, false, false);
+    }
+
+    protected void expectCreate(Class<? extends Connector> connClass,
+                                Class<? extends Task> taskClass,
+                                boolean sink, boolean expectCallback) throws Exception {
+        connectorProps.setProperty(ConnectorConfig.CONNECTOR_CLASS_CONFIG, connClass.getName());
+
+        PowerMock.expectPrivate(StandaloneCoordinator.class, "instantiateConnector", connClass.getName())
+                .andReturn(connector);
+        if (expectCallback) {
+            createCallback.onCompletion(null, CONNECTOR_NAME);
+            PowerMock.expectLastCall();
+        }
+
+        ZkClient zkClient = PowerMock.createMock(ZkClient.class);
+        EasyMock.expect(worker.getZkClient()).andStubReturn(zkClient);
+        connector.initialize(EasyMock.anyObject(StandaloneConnectorContext.class));
+        PowerMock.expectLastCall();
+        connector.start(new Properties());
+        PowerMock.expectLastCall();
+
+        // Just return the connector properties for the individual task we generate by default
+        EasyMock.<Class<? extends Task>>expect(connector.getTaskClass()).andReturn(taskClass);
+
+        if (sink) {
+            EasyMock.expect(KafkaUtils.getTopicPartitions(zkClient, TOPICS_LIST))
+                    .andReturn(TOPIC_PARTITIONS);
+        }
+
+        EasyMock.expect(connector.getTaskConfigs(ConnectorConfig.TASKS_MAX_DEFAULT))
+                .andReturn(Arrays.asList(taskProps));
+        // And we should instantiate the tasks. For a sink task, we should see added properties for
+        // the input topic partitions
+        Properties generatedTaskProps = new Properties();
+        generatedTaskProps.putAll(taskProps);
+        if (sink) {
+            generatedTaskProps.setProperty(SinkTask.TOPICPARTITIONS_CONFIG, TOPIC_PARTITIONS_STR);
+        }
+        worker.addTask(new ConnectorTaskId(CONNECTOR_NAME, 0), taskClass.getName(), generatedTaskProps);
+        PowerMock.expectLastCall();
+    }
+
+    protected void expectStop() throws CopycatException {
+        worker.stopTask(new ConnectorTaskId(CONNECTOR_NAME, 0));
+        EasyMock.expectLastCall();
+        connector.stop();
+        EasyMock.expectLastCall();
+    }
+
+    protected void expectDestroy() throws CopycatException {
+        expectStop();
+    }
+
+    // We need to use a real class here due to some issue with mocking java.lang.Class
+    protected abstract class BogusSourceClass extends SourceConnector {
+    }
+
+    protected abstract class BogusSourceTask extends SourceTask {
+    }
+
+    protected abstract class BogusSinkClass extends SinkConnector {
+    }
+
+    protected abstract class BogusSinkTask extends SourceTask {
+    }
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/storage/FileOffsetBackingStoreTest.java

@@ -0,0 +1,120 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.storage;
+
+import org.apache.kafka.copycat.util.Callback;
+import org.easymock.EasyMock;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.powermock.api.easymock.PowerMock;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+
+import static org.junit.Assert.assertEquals;
+
+public class FileOffsetBackingStoreTest {
+
+    FileOffsetBackingStore store;
+    Properties props;
+    File tempFile;
+
+    private static Map<ByteBuffer, ByteBuffer> firstSet = new HashMap<ByteBuffer, ByteBuffer>();
+
+    static {
+        firstSet.put(buffer("key"), buffer("value"));
+        firstSet.put(null, null);
+    }
+
+    @Before
+    public void setup() throws IOException {
+        store = new FileOffsetBackingStore();
+        tempFile = File.createTempFile("fileoffsetbackingstore", null);
+        props = new Properties();
+        props.setProperty(FileOffsetBackingStore.OFFSET_STORAGE_FILE_FILENAME_CONFIG,
+                tempFile.getAbsolutePath());
+        store.configure(props);
+        store.start();
+    }
+
+    @After
+    public void teardown() {
+        tempFile.delete();
+    }
+
+    @Test
+    public void testGetSet() throws Exception {
+        Callback<Void> setCallback = expectSuccessfulSetCallback();
+        Callback<Map<ByteBuffer, ByteBuffer>> getCallback = expectSuccessfulGetCallback();
+        PowerMock.replayAll();
+
+        store.set("namespace", firstSet, setCallback).get();
+
+        Map<ByteBuffer, ByteBuffer> values
+                = store.get("namespace", Arrays.asList(buffer("key"), buffer("bad")), getCallback).get();
+        assertEquals(buffer("value"), values.get(buffer("key")));
+        assertEquals(null, values.get(buffer("bad")));
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testSaveRestore() throws Exception {
+        Callback<Void> setCallback = expectSuccessfulSetCallback();
+        Callback<Map<ByteBuffer, ByteBuffer>> getCallback = expectSuccessfulGetCallback();
+        PowerMock.replayAll();
+
+        store.set("namespace", firstSet, setCallback).get();
+        store.stop();
+
+        // Restore into a new store to ensure correct reload from scratch
+        FileOffsetBackingStore restore = new FileOffsetBackingStore();
+        restore.configure(props);
+        restore.start();
+        Map<ByteBuffer, ByteBuffer> values
+                = restore.get("namespace", Arrays.asList(buffer("key")), getCallback).get();
+        assertEquals(buffer("value"), values.get(buffer("key")));
+
+        PowerMock.verifyAll();
+    }
+
+    private static ByteBuffer buffer(String v) {
+        return ByteBuffer.wrap(v.getBytes());
+    }
+
+    private Callback<Void> expectSuccessfulSetCallback() {
+        Callback<Void> setCallback = PowerMock.createMock(Callback.class);
+        setCallback.onCompletion(null, null);
+        PowerMock.expectLastCall();
+        return setCallback;
+    }
+
+    private Callback<Map<ByteBuffer, ByteBuffer>> expectSuccessfulGetCallback() {
+        Callback<Map<ByteBuffer, ByteBuffer>> getCallback
+                = PowerMock.createMock(Callback.class);
+        getCallback.onCompletion(EasyMock.isNull(Throwable.class), EasyMock.anyObject(Map.class));
+        PowerMock.expectLastCall();
+        return getCallback;
+    }
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/storage/OffsetStorageWriterTest.java

@@ -0,0 +1,233 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.storage;
+
+import org.apache.kafka.copycat.errors.CopycatRuntimeException;
+import org.apache.kafka.copycat.util.Callback;
+import org.easymock.Capture;
+import org.easymock.EasyMock;
+import org.easymock.IAnswer;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.powermock.api.easymock.PowerMock;
+
+import java.nio.ByteBuffer;
+import java.util.Collections;
+import java.util.Map;
+import java.util.concurrent.*;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class OffsetStorageWriterTest {
+    private static final String NAMESPACE = "namespace";
+    private static final String OFFSET_KEY = "key";
+    private static final String OFFSET_VALUE = "value";
+    private static final String OFFSET_KEY_CONVERTED = "key-converted";
+    private static final String OFFSET_VALUE_CONVERTED = "value-converted";
+    private static final byte[] OFFSET_KEY_SERIALIZED = "key-serialized".getBytes();
+    private static final byte[] OFFSET_VALUE_SERIALIZED = "value-serialized".getBytes();
+    private static final Map<ByteBuffer, ByteBuffer> OFFSETS_SERIALIZED
+            = Collections.singletonMap(ByteBuffer.wrap(OFFSET_KEY_SERIALIZED),
+            ByteBuffer.wrap(OFFSET_VALUE_SERIALIZED));
+
+    private OffsetBackingStore store;
+    private Converter converter;
+    private OffsetSerializer keySerializer;
+    private OffsetSerializer valueSerializer;
+    private OffsetStorageWriter writer;
+
+    private static Exception exception = new RuntimeException("error");
+
+    private ExecutorService service;
+
+    @Before
+    public void setup() {
+        store = PowerMock.createMock(OffsetBackingStore.class);
+        converter = PowerMock.createMock(Converter.class);
+        keySerializer = PowerMock.createMock(OffsetSerializer.class);
+        valueSerializer = PowerMock.createMock(OffsetSerializer.class);
+        writer = new OffsetStorageWriter(store, NAMESPACE, converter, keySerializer, valueSerializer);
+
+        service = Executors.newFixedThreadPool(1);
+    }
+
+    @After
+    public void teardown() {
+        service.shutdownNow();
+    }
+
+    @Test
+    public void testWriteFlush() throws Exception {
+        Callback<Void> callback = PowerMock.createMock(Callback.class);
+        expectStore(callback, false);
+
+        PowerMock.replayAll();
+
+        writer.setOffset(OFFSET_KEY, OFFSET_VALUE);
+
+        assertTrue(writer.beginFlush());
+        writer.doFlush(callback).get(1000, TimeUnit.MILLISECONDS);
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testNoOffsetsToFlush() {
+        // If no offsets are flushed, we should finish immediately and not have made any calls to the
+        // underlying storage layer
+
+        PowerMock.replayAll();
+
+        // Should not return a future
+        assertFalse(writer.beginFlush());
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testFlushFailureReplacesOffsets() throws Exception {
+        // When a flush fails, we shouldn't just lose the offsets. Instead, they should be restored
+        // such that a subsequent flush will write them.
+
+        final Callback<Void> callback = PowerMock.createMock(Callback.class);
+        // First time the write fails
+        expectStore(callback, true);
+        // Second time it succeeds
+        expectStore(callback, false);
+        // Third time it has no data to flush so we won't get past beginFlush()
+
+        PowerMock.replayAll();
+
+        writer.setOffset(OFFSET_KEY, OFFSET_VALUE);
+        assertTrue(writer.beginFlush());
+        writer.doFlush(callback).get(1000, TimeUnit.MILLISECONDS);
+        assertTrue(writer.beginFlush());
+        writer.doFlush(callback).get(1000, TimeUnit.MILLISECONDS);
+        assertFalse(writer.beginFlush());
+
+        PowerMock.verifyAll();
+    }
+
+    @Test(expected = CopycatRuntimeException.class)
+    public void testAlreadyFlushing() throws Exception {
+        final Callback<Void> callback = PowerMock.createMock(Callback.class);
+        // Trigger the send, but don't invoke the callback so we'll still be mid-flush
+        CountDownLatch allowStoreCompleteCountdown = new CountDownLatch(1);
+        expectStore(null, false, allowStoreCompleteCountdown);
+
+        PowerMock.replayAll();
+
+        writer.setOffset(OFFSET_KEY, OFFSET_VALUE);
+        assertTrue(writer.beginFlush());
+        writer.doFlush(callback);
+        assertTrue(writer.beginFlush()); // should throw
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testCancelBeforeAwaitFlush() {
+        PowerMock.replayAll();
+
+        writer.setOffset(OFFSET_KEY, OFFSET_VALUE);
+        assertTrue(writer.beginFlush());
+        writer.cancelFlush();
+
+        PowerMock.verifyAll();
+    }
+
+    @Test
+    public void testCancelAfterAwaitFlush() throws Exception {
+        Callback<Void> callback = PowerMock.createMock(Callback.class);
+        CountDownLatch allowStoreCompleteCountdown = new CountDownLatch(1);
+        // In this test, the write should be cancelled so the callback will not be invoked and is not
+        // passed to the expectStore call
+        expectStore(null, false, allowStoreCompleteCountdown);
+
+        PowerMock.replayAll();
+
+        writer.setOffset(OFFSET_KEY, OFFSET_VALUE);
+        assertTrue(writer.beginFlush());
+        // Start the flush, then immediately cancel before allowing the mocked store request to finish
+        Future<Void> flushFuture = writer.doFlush(callback);
+        writer.cancelFlush();
+        allowStoreCompleteCountdown.countDown();
+        flushFuture.get(1000, TimeUnit.MILLISECONDS);
+
+        PowerMock.verifyAll();
+    }
+
+    private void expectStore(final Callback<Void> callback, final boolean fail) {
+        expectStore(callback, fail, null);
+    }
+
+    /**
+     * Expect a request to store data to the underlying OffsetBackingStore.
+     *
+     * @param callback the callback to invoke when completed, or null if the callback isn't
+     *                 expected to be invoked
+     * @param fail if true, treat
+     * @param waitForCompletion if non-null, a CountDownLatch that should be awaited on before
+     *                          invoking the callback. A (generous) timeout is still imposed to
+     *                          ensure tests complete.
+     * @return the captured set of ByteBuffer key-value pairs passed to the storage layer
+     */
+    private void expectStore(final Callback<Void> callback,
+                             final boolean fail,
+                             final CountDownLatch waitForCompletion) {
+        EasyMock.expect(converter.fromCopycatData(OFFSET_KEY)).andReturn(OFFSET_KEY_CONVERTED);
+        EasyMock.expect(keySerializer.serializeOffset(NAMESPACE, OFFSET_KEY_CONVERTED)).andReturn(OFFSET_KEY_SERIALIZED);
+        EasyMock.expect(converter.fromCopycatData(OFFSET_VALUE)).andReturn(OFFSET_VALUE_CONVERTED);
+        EasyMock.expect(valueSerializer.serializeOffset(NAMESPACE, OFFSET_VALUE_CONVERTED)).andReturn(OFFSET_VALUE_SERIALIZED);
+
+        final Capture<Callback<Void>> storeCallback = Capture.newInstance();
+        EasyMock.expect(store.set(EasyMock.eq(NAMESPACE), EasyMock.eq(OFFSETS_SERIALIZED),
+                EasyMock.capture(storeCallback)))
+                .andAnswer(new IAnswer<Future<Void>>() {
+                    @Override
+                    public Future<Void> answer() throws Throwable {
+                        return service.submit(new Callable<Void>() {
+                            @Override
+                            public Void call() throws Exception {
+                                if (waitForCompletion != null) {
+                                    assertTrue(waitForCompletion.await(10000, TimeUnit.MILLISECONDS));
+                                }
+
+                                if (fail) {
+                                    storeCallback.getValue().onCompletion(exception, null);
+                                } else {
+                                    storeCallback.getValue().onCompletion(null, null);
+                                }
+                                return null;
+                            }
+                        });
+                    }
+                });
+        if (callback != null) {
+            if (fail) {
+                callback.onCompletion(EasyMock.eq(exception), EasyMock.eq((Void) null));
+            } else {
+                callback.onCompletion(null, null);
+            }
+        }
+        PowerMock.expectLastCall();
+    }
+
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/util/MockTime.java

@@ -16,30 +16,34 @@
  **/
 package org.apache.kafka.copycat.util;
 
-/**
- * General string utilities that are missing from the standard library and may commonly be
- * required by Connector or Task implementations.
- */
-public class StringUtils {
+import org.apache.kafka.common.utils.Time;
 
-    /**
-     * Generate a String by appending all the @{elements}, converted to Strings, delimited by
-     * @{delim}.
-     * @param elements list of elements to concatenate
-     * @param delim delimiter to place between each element
-     * @return the concatenated string with delimiters
-     */
-    public static <T> String join(Iterable<T> elements, String delim) {
-        StringBuilder result = new StringBuilder();
-        boolean first = true;
-        for (T elem : elements) {
-            if (first) {
-                first = false;
-            } else {
-                result.append(delim);
-            }
-            result.append(elem);
-        }
-        return result.toString();
+import java.util.concurrent.TimeUnit;
+
+/**
+ * A clock that you can manually advance by calling sleep
+ */
+public class MockTime implements Time {
+
+    private long nanos = 0;
+
+    public MockTime() {
+        this.nanos = System.nanoTime();
     }
+
+    @Override
+    public long milliseconds() {
+        return TimeUnit.MILLISECONDS.convert(this.nanos, TimeUnit.NANOSECONDS);
+    }
+
+    @Override
+    public long nanoseconds() {
+        return nanos;
+    }
+
+    @Override
+    public void sleep(long ms) {
+        this.nanos += TimeUnit.NANOSECONDS.convert(ms, TimeUnit.MILLISECONDS);
+    }
+
 }

copycat-runtime/src/test/java/org/apache/kafka/copycat/util/ShutdownableThreadTest.java

@@ -0,0 +1,72 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.util;
+
+import org.junit.Test;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class ShutdownableThreadTest {
+
+    @Test
+    public void testGracefulShutdown() throws InterruptedException {
+        ShutdownableThread thread = new ShutdownableThread("graceful") {
+            @Override
+            public void execute() {
+                while (getRunning()) {
+                    try {
+                        Thread.sleep(1);
+                    } catch (InterruptedException e) {
+                        // Ignore
+                    }
+                }
+            }
+        };
+        thread.start();
+        Thread.sleep(10);
+        assertTrue(thread.gracefulShutdown(1000, TimeUnit.MILLISECONDS));
+    }
+
+    @Test
+    public void testForcibleShutdown() throws InterruptedException {
+        final CountDownLatch startedLatch = new CountDownLatch(1);
+        ShutdownableThread thread = new ShutdownableThread("forcible") {
+            @Override
+            public void execute() {
+                try {
+                    startedLatch.countDown();
+                    Thread.sleep(100000);
+                } catch (InterruptedException e) {
+                    // Ignore
+                }
+            }
+        };
+        thread.start();
+        startedLatch.await();
+        thread.forceShutdown();
+        // Not all threads can be forcibly stopped since interrupt() doesn't work on threads in
+        // certain conditions, but in this case we know the thread is interruptible so we should be
+        // able join() it
+        thread.join(1000);
+        assertFalse(thread.isAlive());
+    }
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/util/TestBackgroundThreadExceptionHandler.java

@@ -0,0 +1,39 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.util;
+
+/**
+ * An UncaughtExceptionHandler that can be registered with one or more threads which tracks the
+ * first exception so the main thread can check for uncaught exceptions.
+ */
+public class TestBackgroundThreadExceptionHandler implements Thread.UncaughtExceptionHandler {
+    private Throwable firstException = null;
+
+    @Override
+    public void uncaughtException(Thread t, Throwable e) {
+        if (this.firstException == null) {
+            this.firstException = e;
+        }
+    }
+
+    public void verifyNoExceptions() {
+        if (this.firstException != null) {
+            throw new AssertionError(this.firstException);
+        }
+    }
+}

copycat-runtime/src/test/java/org/apache/kafka/copycat/util/ThreadedTest.java

@@ -0,0 +1,43 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+package org.apache.kafka.copycat.util;
+
+import org.junit.After;
+import org.junit.Before;
+
+/**
+ * Base class for tests that use threads. It sets up uncaught exception handlers for all known
+ * thread classes and checks for errors at the end of the test so that failures in background
+ * threads will cause the test to fail.
+ */
+public class ThreadedTest {
+
+    protected TestBackgroundThreadExceptionHandler backgroundThreadExceptionHandler;
+
+    @Before
+    public void setup() {
+        backgroundThreadExceptionHandler = new TestBackgroundThreadExceptionHandler();
+        ShutdownableThread.funcaughtExceptionHandler = backgroundThreadExceptionHandler;
+    }
+
+    @After
+    public void teardown() {
+        backgroundThreadExceptionHandler.verifyNoExceptions();
+        ShutdownableThread.funcaughtExceptionHandler = null;
+    }
+}

settings.gradle

@@ -15,4 +15,4 @@
 
 apply from: file('scala.gradle')
 include 'core', 'contrib:hadoop-consumer', 'contrib:hadoop-producer', 'examples', 'clients',
-        'log4j-appender', 'copycat-data', 'copycat-api'
+        'log4j-appender', 'copycat-data', 'copycat-api', 'copycat-runtime', 'copycat-avro'