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KAFKA-8816: Make offsets immutable to users of RecordCollector.offsets #7223

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Merged
guozhangwang merged 4 commits into from
Aug 26, 2019
Merged

KAFKA-8816: Make offsets immutable to users of RecordCollector.offsets #7223

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c540b38
KAFKA-8816: Make offsets immutable to users of RecordCollector.offsets
cpettitt-confluent Aug 19, 2019
c51b92c
Review fixes, to be squashed
cpettitt-confluent Aug 20, 2019
b44b9af
More improvements based on review feedback
cpettitt-confluent Aug 26, 2019
2e0fd82
Tweak docs to reflect behavior change, cosmetic cleanup
cpettitt-confluent Aug 26, 2019
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2 changes: 1 addition & 1 deletion streams/src/main/java/org/apache/kafka/streams/processor/internals/RecordCollector.java
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Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,7 @@ <K, V> void send(final String topic,
/**
* The last acked offsets from the internal {@link Producer}.
*
* @return the map from TopicPartition to offset
* @return an immutable map from TopicPartition to offset
*/
Map<TopicPartition, Long> offsets();

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3 changes: 2 additions & 1 deletion streams/src/main/java/org/apache/kafka/streams/processor/internals/RecordCollectorImpl.java
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Expand Up @@ -16,6 +16,7 @@
*/
package org.apache.kafka.streams.processor.internals;

import java.util.Collections;
import org.apache.kafka.clients.producer.Callback;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;
Expand Down Expand Up @@ -279,7 +280,7 @@ public void close() {

@Override
public Map<TopicPartition, Long> offsets() {
return offsets;
return Collections.unmodifiableMap(offsets);

@mjsax mjsax Aug 20, 2019

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Would it be simpler to hand out a deep copy of the map directly?

@cpettitt-confluent cpettitt-confluent Aug 20, 2019

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That would be totally fine for the current usage pattern, where we have a single query that ends up copying the map anyway. However, if we ever ended up with other queries then those queries would pay the cost of the copy whether they need it or not. It would be a bit surprising that a copy is happening without looking at the implementation. My bias would be towards defensive coding without surprise performance impact.

@mjsax mjsax Aug 21, 2019

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Fair enough.

}

// for testing only
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3 changes: 2 additions & 1 deletion streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamTask.java
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Expand Up @@ -486,7 +486,8 @@ void commit(final boolean startNewTransaction) {

@Override
protected Map<TopicPartition, Long> activeTaskCheckpointableOffsets() {
final Map<TopicPartition, Long> checkpointableOffsets = recordCollector.offsets();
final Map<TopicPartition, Long> checkpointableOffsets =
new HashMap<>(recordCollector.offsets());
for (final Map.Entry<TopicPartition, Long> entry : consumedOffsets.entrySet()) {
checkpointableOffsets.putIfAbsent(entry.getKey(), entry.getValue());
}
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28 changes: 28 additions & 0 deletions streams/src/test/java/org/apache/kafka/streams/processor/internals/RecordCollectorTest.java
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Expand Up @@ -50,7 +50,10 @@
import java.util.Map;
import java.util.concurrent.Future;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.equalTo;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertThrows;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;

Expand Down Expand Up @@ -145,6 +148,31 @@ public void testStreamPartitioner() {
assertEquals((Long) 0L, offsets.get(new TopicPartition("topic1", 2)));
}

@Test
public void shouldNotAllowOffsetsToBeUpdatedExternally() {
final String topic = "topic1";
final TopicPartition topicPartition = new TopicPartition(topic, 0);

final RecordCollectorImpl collector = new RecordCollectorImpl(
"RecordCollectorTest-TestSpecificPartition",
new LogContext("RecordCollectorTest-TestSpecificPartition "),
new DefaultProductionExceptionHandler(),
new Metrics().sensor("skipped-records")
);
collector.init(new MockProducer<>(cluster, true, new DefaultPartitioner(), byteArraySerializer, byteArraySerializer));

collector.send(topic, "999", "0", null, 0, null, stringSerializer, stringSerializer);
collector.send(topic, "999", "0", null, 0, null, stringSerializer, stringSerializer);
collector.send(topic, "999", "0", null, 0, null, stringSerializer, stringSerializer);

final Map<TopicPartition, Long> offsets = collector.offsets();

assertThat(offsets.get(topicPartition), equalTo(2L));
assertThrows(UnsupportedOperationException.class, () -> offsets.put(new TopicPartition(topic, 0), 50L));

@cadonna cadonna Aug 26, 2019

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nit: I would remove this line

@cpettitt-confluent cpettitt-confluent Aug 26, 2019

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I would argue for keeping this because the change impacts the external behavior of the class. We're making a strong statement here: you will get an exception if you try to modify the contents of the returned map, you must copy this map if you want to make changes. This also distinguishes from the alternative approach we could have used in which we proactively copy the map for the user and where the user could have made a change to the map while still not impacting the underlying map. Given that this is externally facing and there is doc a couple levels up, I will fix that up.

Happy to discuss further if you strongly disagree.

assertThat(collector.offsets().get(topicPartition), equalTo(2L));
}

@SuppressWarnings("unchecked")
@Test(expected = StreamsException.class)
public void shouldThrowStreamsExceptionOnAnyExceptionButProducerFencedException() {
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