KAFKA-6560: [FOLLOW-UP] don't deserialize null byte array in window store fetch (#4665)

If the result of a fetch from a Window Store results in a null byte array we should return null rather than passing it to the serde to deserialize.

Reviewers: Guozhang Wang <wangguoz@gmail.com>

streams/src/main/java/org/apache/kafka/streams/state/internals/MeteredWindowStore.java

@@ -106,15 +106,15 @@ public class MeteredWindowStore<K, V> extends WrappedStateStore.AbstractStateSto
     @Override
     public V fetch(final K key, final long timestamp) {
         final long startNs = time.nanoseconds();
-        V ret;
         try {
             final byte[] result = inner.fetch(keyBytes(key), timestamp);
-            ret = serdes.valueFrom(result);
+            if (result == null) {
+                return null;
+            }
+            return serdes.valueFrom(result);
         } finally {
             metrics.recordLatency(this.fetchTime, startNs, time.nanoseconds());
         }
-
-        return ret;
     }
 
     @Override

streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBWindowStore.java

@@ -110,6 +110,9 @@ public class RocksDBWindowStore<K, V> extends WrappedStateStore.AbstractStateSto
     @Override
     public V fetch(final K key, final long timestamp) {
         final byte[] bytesValue = bytesStore.get(WindowStoreUtils.toBinaryKey(key, timestamp, seqnum, serdes));
+        if (bytesValue == null) {
+            return null;
+        }
         return serdes.valueFrom(bytesValue);
     }
 

streams/src/test/java/org/apache/kafka/streams/state/internals/CachingKeyValueStoreTest.java

@@ -81,6 +81,7 @@ public class CachingKeyValueStoreTest extends AbstractKeyValueStoreTest {
 
     @After
     public void after() {
+        super.after();
         context.close();
     }
 

streams/src/test/java/org/apache/kafka/streams/state/internals/CachingSessionStoreTest.java

@@ -28,7 +28,6 @@ import org.apache.kafka.streams.kstream.internals.Change;
 import org.apache.kafka.streams.kstream.internals.SessionWindow;
 import org.apache.kafka.streams.processor.internals.MockStreamsMetrics;
 import org.apache.kafka.streams.processor.internals.ProcessorRecordContext;
-import org.apache.kafka.streams.processor.internals.RecordCollector;
 import org.apache.kafka.streams.state.KeyValueIterator;
 import org.apache.kafka.streams.state.StateSerdes;
 import org.apache.kafka.test.MockProcessorContext;
@@ -76,7 +75,7 @@ public class CachingSessionStoreTest {
                                                  Segments.segmentInterval(retention, numSegments)
                                                  );
         cache = new ThreadCache(new LogContext("testCache "), MAX_CACHE_SIZE_BYTES, new MockStreamsMetrics(new Metrics()));
-        context = new MockProcessorContext(TestUtils.tempDirectory(), null, null, (RecordCollector) null, cache);
+        context = new MockProcessorContext(TestUtils.tempDirectory(), null, null, null, cache);
         context.setRecordContext(new ProcessorRecordContext(DEFAULT_TIMESTAMP, 0, 0, "topic"));
         cachingStore.init(context, cachingStore);
     }
@@ -87,10 +86,6 @@ public class CachingSessionStoreTest {
         cachingStore.close();
     }
 
-    private Bytes bytesKey(final String key) {
-        return Bytes.wrap(key.getBytes());
-    }
-
     @Test
     public void shouldPutFetchFromCache() {
         cachingStore.put(new Windowed<>(keyA, new SessionWindow(0, 0)), "1".getBytes());

streams/src/test/java/org/apache/kafka/streams/state/internals/ChangeLoggingSessionBytesStoreTest.java

@@ -69,9 +69,8 @@ public class ChangeLoggingSessionBytesStoreTest {
     private final Windowed<Bytes> key1 = new Windowed<>(bytesKey, new SessionWindow(0, 0));
 
     @Before
-    public void setUp() throws Exception {
+    public void setUp() {
         store = new ChangeLoggingSessionBytesStore(inner);
-
     }
 
     private void init() {

streams/src/test/java/org/apache/kafka/streams/state/internals/MeteredWindowStoreTest.java

@@ -40,13 +40,14 @@ import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
 public class MeteredWindowStoreTest {
     private MockProcessorContext context;
     @SuppressWarnings("unchecked")
     private final WindowStore<Bytes, byte[]> innerStoreMock = EasyMock.createNiceMock(WindowStore.class);
-    private final MeteredWindowStore<String, String> store = new MeteredWindowStore<>(innerStoreMock, "scope", new MockTime(), Serdes.String(), Serdes.String());
+    private final MeteredWindowStore<String, String> store = new MeteredWindowStore<>(innerStoreMock, "scope", new MockTime(), Serdes.String(), new SerdeThatDoesntHandleNull());
     private final Set<String> latencyRecorded = new HashSet<>();
     private final Set<String> throughputRecorded = new HashSet<>();
 
@@ -118,7 +119,7 @@ public class MeteredWindowStoreTest {
     }
 
     @Test
-    public void shouldRecordRestoreLatencyOnInit() throws Exception {
+    public void shouldRecordRestoreLatencyOnInit() {
         innerStoreMock.init(context, store);
         EasyMock.expectLastCall();
         EasyMock.replay(innerStoreMock);
@@ -127,7 +128,7 @@ public class MeteredWindowStoreTest {
     }
 
     @Test
-    public void shouldRecordPutLatency() throws Exception {
+    public void shouldRecordPutLatency() {
         final byte[] bytes = "a".getBytes();
         innerStoreMock.put(EasyMock.eq(Bytes.wrap(bytes)), EasyMock.<byte[]>anyObject(), EasyMock.eq(context.timestamp()));
         EasyMock.expectLastCall();
@@ -140,7 +141,7 @@ public class MeteredWindowStoreTest {
     }
 
     @Test
-    public void shouldRecordFetchLatency() throws Exception {
+    public void shouldRecordFetchLatency() {
         EasyMock.expect(innerStoreMock.fetch(Bytes.wrap("a".getBytes()), 1, 1)).andReturn(KeyValueIterators.<byte[]>emptyWindowStoreIterator());
         EasyMock.replay(innerStoreMock);
 
@@ -151,7 +152,7 @@ public class MeteredWindowStoreTest {
     }
 
     @Test
-    public void shouldRecordFetchRangeLatency() throws Exception {
+    public void shouldRecordFetchRangeLatency() {
         EasyMock.expect(innerStoreMock.fetch(Bytes.wrap("a".getBytes()), Bytes.wrap("b".getBytes()), 1, 1)).andReturn(KeyValueIterators.<Windowed<Bytes>, byte[]>emptyIterator());
         EasyMock.replay(innerStoreMock);
 
@@ -163,7 +164,7 @@ public class MeteredWindowStoreTest {
 
 
     @Test
-    public void shouldRecordFlushLatency() throws Exception {
+    public void shouldRecordFlushLatency() {
         innerStoreMock.flush();
         EasyMock.expectLastCall();
         EasyMock.replay(innerStoreMock);
@@ -176,7 +177,7 @@ public class MeteredWindowStoreTest {
 
 
     @Test
-    public void shouldCloseUnderlyingStore() throws Exception {
+    public void shouldCloseUnderlyingStore() {
         innerStoreMock.close();
         EasyMock.expectLastCall();
         EasyMock.replay(innerStoreMock);
@@ -187,4 +188,13 @@ public class MeteredWindowStoreTest {
     }
 
 
+    @Test
+    public void shouldNotExceptionIfFetchReturnsNull() {
+        EasyMock.expect(innerStoreMock.fetch(Bytes.wrap("a".getBytes()), 0)).andReturn(null);
+        EasyMock.replay(innerStoreMock);
+
+        store.init(context, store);
+        assertNull(store.fetch("a", 0));
+    }
+
 }

streams/src/test/java/org/apache/kafka/streams/state/internals/RocksDBKeyValueStoreTest.java

@@ -51,7 +51,6 @@ public class RocksDBKeyValueStoreTest extends AbstractKeyValueStoreTest {
     }
 
     public static class TheRocksDbConfigSetter implements RocksDBConfigSetter {
-
         static boolean called = false;
 
         @Override

streams/src/test/java/org/apache/kafka/streams/state/internals/RocksDBStoreTest.java

@@ -79,6 +79,7 @@ public class RocksDBStoreTest {
     @After
     public void tearDown() {
         rocksDBStore.close();
+        context.close();
     }
 
     @Test

streams/src/test/java/org/apache/kafka/streams/state/internals/RocksDBWindowStoreTest.java

@@ -795,6 +795,19 @@ public class RocksDBWindowStoreTest {
         windowStore.fetch(1, null, 1L, 2L);
     }
 
+    @Test
+    public void shouldNoNullPointerWhenSerdeDoesntHandleNull() {
+        windowStore = new RocksDBWindowStore<>(
+                new RocksDBSegmentedBytesStore(windowName, retentionPeriod, numSegments, new WindowKeySchema()),
+                Serdes.Integer(),
+                new SerdeThatDoesntHandleNull(),
+                false,
+                windowSize);
+        windowStore.init(context, windowStore);
+
+        assertNull(windowStore.fetch(1, 0));
+    }
+
     @Test
     public void shouldFetchAndIterateOverExactBinaryKeys() {
         final WindowStore<Bytes, String> windowStore = Stores.windowStoreBuilder(

streams/src/test/java/org/apache/kafka/streams/state/internals/SerdeThatDoesntHandleNull.java

@@ -0,0 +1,55 @@
+/*
+ * 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
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.streams.state.internals;
+
+import org.apache.kafka.common.serialization.Deserializer;
+import org.apache.kafka.common.serialization.Serde;
+import org.apache.kafka.common.serialization.Serializer;
+import org.apache.kafka.common.serialization.StringDeserializer;
+import org.apache.kafka.common.serialization.StringSerializer;
+
+import java.util.Map;
+
+class SerdeThatDoesntHandleNull implements Serde<String> {
+    @Override
+    public void configure(final Map<String, ?> configs, final boolean isKey) {
+
+    }
+
+    @Override
+    public void close() {
+
+    }
+
+    @Override
+    public Serializer<String> serializer() {
+        return new StringSerializer();
+    }
+
+    @Override
+    public Deserializer<String> deserializer() {
+        return new StringDeserializer() {
+            @Override
+            public String deserialize(final String topic, final byte[] data) {
+                if (data == null) {
+                    throw new NullPointerException();
+                }
+                return super.deserialize(topic, data);
+            }
+        };
+    }
+}