Mark Copycat classes as unstable and reduce visibility of some classes where possible.

checkstyle/import-control.xml

@@ -109,6 +109,7 @@
 	</subpackage>
 
 	<subpackage name="copycat">
+		<allow pkg="org.apache.kafka.common" />
 		<allow pkg="org.apache.kafka.copycat.data" />
 		<allow pkg="org.apache.kafka.copycat.errors" />
 
@@ -124,7 +125,6 @@
 
 		<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" />

copycat/api/src/main/java/org/apache/kafka/copycat/connector/Connector.java

@@ -17,6 +17,7 @@
 
 package org.apache.kafka.copycat.connector;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.copycat.errors.CopycatException;
 
 import java.util.List;
@@ -39,6 +40,7 @@ import java.util.Properties;
  * Tasks.
  * </p>
  */
+@InterfaceStability.Unstable
 public abstract class Connector {
 
     protected ConnectorContext context;

copycat/api/src/main/java/org/apache/kafka/copycat/connector/ConnectorContext.java

@@ -17,9 +17,12 @@
 
 package org.apache.kafka.copycat.connector;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
+
 /**
  * ConnectorContext allows Connectors to proactively interact with the Copycat runtime.
  */
+@InterfaceStability.Unstable
 public interface ConnectorContext {
     /**
      * Requests that the runtime reconfigure the Tasks for this source. This should be used to

copycat/api/src/main/java/org/apache/kafka/copycat/connector/CopycatRecord.java

@@ -17,6 +17,8 @@
 
 package org.apache.kafka.copycat.connector;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
+
 /**
  * <p>
  * Base class for records containing data to be copied to/from Kafka. This corresponds closely to
@@ -25,6 +27,7 @@ package org.apache.kafka.copycat.connector;
  * notion of offset, it is not included here because they differ in type.
  * </p>
  */
+@InterfaceStability.Unstable
 public abstract class CopycatRecord {
     private final String topic;
     private final Integer kafkaPartition;

copycat/api/src/main/java/org/apache/kafka/copycat/connector/Task.java

@@ -17,6 +17,7 @@
 
 package org.apache.kafka.copycat.connector;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.copycat.errors.CopycatException;
 
 import java.util.Properties;
@@ -34,6 +35,7 @@ import java.util.Properties;
  * {@link org.apache.kafka.copycat.sink.SinkTask}.
  * </p>
  */
+@InterfaceStability.Unstable
 public interface Task {
     /**
      * Start the Task

copycat/api/src/main/java/org/apache/kafka/copycat/errors/CopycatException.java

@@ -17,9 +17,12 @@
 
 package org.apache.kafka.copycat.errors;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
+
 /**
  * CopycatException is the top-level exception type generated by Copycat and connectors.
  */
+@InterfaceStability.Unstable
 public class CopycatException extends Exception {
 
     public CopycatException(String s) {

copycat/api/src/main/java/org/apache/kafka/copycat/errors/CopycatRuntimeException.java

@@ -17,6 +17,9 @@
 
 package org.apache.kafka.copycat.errors;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
+
+@InterfaceStability.Unstable
 public class CopycatRuntimeException extends RuntimeException {
     public CopycatRuntimeException(String s) {
         super(s);

copycat/api/src/main/java/org/apache/kafka/copycat/sink/SinkConnector.java

@@ -17,11 +17,13 @@
 
 package org.apache.kafka.copycat.sink;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.copycat.connector.Connector;
 
 /**
  * SinkConnectors implement the Connector interface to send Kafka data to another system.
  */
+@InterfaceStability.Unstable
 public abstract class SinkConnector extends Connector {
 
     /**

copycat/api/src/main/java/org/apache/kafka/copycat/sink/SinkRecord.java

@@ -17,6 +17,7 @@
 
 package org.apache.kafka.copycat.sink;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.copycat.connector.CopycatRecord;
 
 /**
@@ -24,6 +25,7 @@ import org.apache.kafka.copycat.connector.CopycatRecord;
  * the record in the Kafka topic-partition in addition to the standard fields. This information
  * should be used by the SinkTask to coordinate kafkaOffset commits.
  */
+@InterfaceStability.Unstable
 public class SinkRecord extends CopycatRecord {
     private final long kafkaOffset;
 

copycat/api/src/main/java/org/apache/kafka/copycat/sink/SinkTask.java

@@ -17,6 +17,7 @@
 package org.apache.kafka.copycat.sink;
 
 import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.copycat.connector.Task;
 import org.apache.kafka.copycat.errors.CopycatException;
 
@@ -28,6 +29,7 @@ import java.util.Map;
  * addition to the basic {@link #put} interface, SinkTasks must also implement {@link #flush}
  * to support offset commits.
  */
+@InterfaceStability.Unstable
 public abstract class SinkTask implements Task {
 
     /**

copycat/api/src/main/java/org/apache/kafka/copycat/sink/SinkTaskContext.java

@@ -18,6 +18,7 @@
 package org.apache.kafka.copycat.sink;
 
 import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.common.annotation.InterfaceStability;
 
 import java.util.HashMap;
 import java.util.Map;
@@ -25,6 +26,7 @@ import java.util.Map;
 /**
  * Context passed to SinkTasks, allowing them to access utilities in the copycat runtime.
  */
+@InterfaceStability.Unstable
 public abstract class SinkTaskContext {
     private Map<TopicPartition, Long> offsets;
 

copycat/api/src/main/java/org/apache/kafka/copycat/source/SourceConnector.java

@@ -16,12 +16,14 @@
  **/
 package org.apache.kafka.copycat.source;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.copycat.connector.Connector;
 
 /**
  * SourceConnectors implement the connector interface to pull data from another system and send
  * it to Kafka.
  */
+@InterfaceStability.Unstable
 public abstract class SourceConnector extends Connector {
 
 }

copycat/api/src/main/java/org/apache/kafka/copycat/source/SourceRecord.java

@@ -17,6 +17,7 @@
 
 package org.apache.kafka.copycat.source;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.copycat.connector.CopycatRecord;
 
 /**
@@ -37,6 +38,7 @@ import org.apache.kafka.copycat.connector.CopycatRecord;
  * "table_name"} and the sourceOffset as a Long containing the timestamp of the row.
  * </p>
  */
+@InterfaceStability.Unstable
 public class SourceRecord extends CopycatRecord {
     private final Object sourcePartition;
     private final Object sourceOffset;

copycat/api/src/main/java/org/apache/kafka/copycat/source/SourceTask.java

@@ -17,6 +17,7 @@
 
 package org.apache.kafka.copycat.source;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.copycat.connector.Task;
 
 import java.util.List;
@@ -24,6 +25,7 @@ import java.util.List;
 /**
  * SourceTask is a Task that pulls records from another system for storage in Kafka.
  */
+@InterfaceStability.Unstable
 public abstract class SourceTask implements Task {
 
     protected SourceTaskContext context;

copycat/api/src/main/java/org/apache/kafka/copycat/source/SourceTaskContext.java

@@ -16,12 +16,14 @@
  **/
 package org.apache.kafka.copycat.source;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.copycat.storage.OffsetStorageReader;
 
 /**
  * SourceTaskContext is provided to SourceTasks to allow them to interact with the underlying
  * runtime.
  */
+@InterfaceStability.Unstable
 public class SourceTaskContext {
     private final OffsetStorageReader reader;
 

copycat/api/src/main/java/org/apache/kafka/copycat/storage/Converter.java

@@ -17,6 +17,8 @@
 
 package org.apache.kafka.copycat.storage;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
+
 /**
  * The Converter interface provides support for translating between Copycat's runtime data format
  * and the "native" runtime format used by the serialization layer. This is used to translate
@@ -24,6 +26,7 @@ package org.apache.kafka.copycat.storage;
  * component -- the producer or consumer serializer or deserializer for records or a Copycat
  * serializer or deserializer for offsets.
  */
+@InterfaceStability.Unstable
 public interface Converter<T> {
 
     /**

copycat/api/src/main/java/org/apache/kafka/copycat/storage/OffsetStorageReader.java

@@ -17,6 +17,8 @@
 
 package org.apache.kafka.copycat.storage;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
+
 import java.util.Collection;
 import java.util.Map;
 
@@ -25,6 +27,7 @@ import java.util.Map;
  * connectors to determine offsets to start consuming data from. This is most commonly used during
  * initialization of a task, but can also be used during runtime, e.g. when reconfiguring a task.
  */
+@InterfaceStability.Unstable
 public interface OffsetStorageReader {
     /**
      * Get the offset for the specified partition. If the data isn't already available locally, this

copycat/api/src/main/java/org/apache/kafka/copycat/util/ConnectorUtils.java

@@ -17,6 +17,8 @@
 
 package org.apache.kafka.copycat.util;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
+
 import java.util.ArrayList;
 import java.util.List;
 
@@ -24,6 +26,7 @@ import java.util.List;
  * Utilities that connector implementations might find useful. Contains common building blocks
  * for writing connectors.
  */
+@InterfaceStability.Unstable
 public class ConnectorUtils {
     /**
      * Given a list of elements and a target number of groups, generates list of groups of

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

@@ -17,6 +17,7 @@
 
 package org.apache.kafka.copycat.cli;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.common.config.ConfigException;
 import org.apache.kafka.common.utils.Utils;
 import org.apache.kafka.copycat.runtime.Coordinator;
@@ -40,6 +41,7 @@ import java.util.Properties;
  * fault tolerant by overriding the settings to use file storage for both.
  * </p>
  */
+@InterfaceStability.Unstable
 public class Copycat {
     private static final Logger log = LoggerFactory.getLogger(Copycat.class);
 

copycat/runtime/src/main/java/org/apache/kafka/copycat/cli/CopycatConfig.java

@@ -17,6 +17,7 @@
 
 package org.apache.kafka.copycat.cli;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.common.config.AbstractConfig;
 import org.apache.kafka.common.config.ConfigDef;
 import org.apache.kafka.common.config.ConfigDef.Importance;
@@ -24,6 +25,7 @@ import org.apache.kafka.common.config.ConfigDef.Type;
 
 import java.util.Properties;
 
+@InterfaceStability.Unstable
 public class CopycatConfig extends AbstractConfig {
 
     public static final String WORKER_PROPERTIES_CONFIG = "worker-config";
@@ -53,11 +55,8 @@ public class CopycatConfig extends AbstractConfig {
                         Importance.HIGH, DELETE_CONNECTORS_CONFIG_DOC);
     }
 
-    private Properties originalProperties;
-
     public CopycatConfig(Properties props) {
         super(config, props);
-        this.originalProperties = props;
     }
 
     /**

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

@@ -17,6 +17,7 @@
 
 package org.apache.kafka.copycat.cli;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.apache.kafka.common.config.AbstractConfig;
 import org.apache.kafka.common.config.ConfigDef;
 import org.apache.kafka.common.config.ConfigDef.Importance;
@@ -28,6 +29,7 @@ import java.util.Set;
 /**
  * Configuration for standalone workers.
  */
+@InterfaceStability.Unstable
 public class WorkerConfig extends AbstractConfig {
 
     public static final String CLUSTER_CONFIG = "cluster";

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

@@ -17,6 +17,7 @@
 
 package org.apache.kafka.copycat.runtime;
 
+import org.apache.kafka.common.annotation.InterfaceStability;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -27,6 +28,7 @@ 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.
  */
+@InterfaceStability.Unstable
 public class Copycat {
     private static final Logger log = LoggerFactory.getLogger(Copycat.class);
 

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

@@ -19,6 +19,6 @@ package org.apache.kafka.copycat.runtime;
 
 import org.apache.kafka.copycat.sink.SinkTaskContext;
 
-public class SinkTaskContextImpl extends SinkTaskContext {
+class SinkTaskContextImpl extends SinkTaskContext {
 
 }

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

@@ -44,7 +44,7 @@ import java.util.concurrent.TimeUnit;
  *   The current implementation uses a single thread to process commits and
  * </p>
  */
-public class SourceTaskOffsetCommitter {
+class SourceTaskOffsetCommitter {
     private static final Logger log = LoggerFactory.getLogger(SourceTaskOffsetCommitter.class);
 
     private Time time;

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

@@ -38,7 +38,7 @@ import java.util.concurrent.TimeUnit;
 /**
  * WorkerTask that uses a SinkTask to export data from Kafka.
  */
-public class WorkerSinkTask<K, V> implements WorkerTask {
+class WorkerSinkTask<K, V> implements WorkerTask {
     private static final Logger log = LoggerFactory.getLogger(WorkerSinkTask.class);
 
     private final ConnectorTaskId id;

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

@@ -46,7 +46,7 @@ import java.util.concurrent.TimeoutException;
 /**
  * WorkerTask that uses a SourceTask to ingest data into Kafka.
  */
-public class WorkerSourceTask<K, V> implements WorkerTask {
+class WorkerSourceTask<K, V> implements WorkerTask {
     private static final Logger log = LoggerFactory.getLogger(WorkerSourceTask.class);
 
     private ConnectorTaskId id;

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

@@ -26,7 +26,7 @@ import java.util.Properties;
  * used by {@link Worker} to manage the tasks. Implementations combine a user-specified Task with
  * Kafka to create a data flow.
  */
-public interface WorkerTask {
+interface WorkerTask {
     /**
      * Start the Task
      * @param props initial configuration

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

@@ -24,7 +24,7 @@ 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 {
+interface ConfigStorage {
 
     /**
      * Configure this storage engine.

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

@@ -23,7 +23,7 @@ import org.apache.kafka.copycat.connector.ConnectorContext;
  * ConnectorContext for use with the StandaloneCoordinator, which maintains all connectors and tasks
  * in a single process.
  */
-public class StandaloneConnectorContext implements ConnectorContext {
+class StandaloneConnectorContext implements ConnectorContext {
 
     private StandaloneCoordinator coordinator;
     private String connectorName;