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MINOR: Fix Streams Position thread-safety #19480

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Merged
merged 3 commits into from
Apr 16, 2025
Merged

MINOR: Fix Streams Position thread-safety #19480

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8f55d76
Add multithreaded position test to repro thread safety issue.
cjf2xn Apr 2, 2025
8cd973c
Fix import order.
cjf2xn Apr 2, 2025
032c4e8
Cleanup.
cjf2xn Apr 2, 2025
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8 changes: 2 additions & 6 deletions streams/src/main/java/org/apache/kafka/streams/query/Position.java
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Original file line number Diff line number Diff line change
Expand Up @@ -104,15 +104,11 @@ public Position merge(final Position other) {
} else {
for (final Entry<String, ConcurrentHashMap<Integer, Long>> entry : other.position.entrySet()) {
final String topic = entry.getKey();
final Map<Integer, Long> partitionMap =
position.computeIfAbsent(topic, k -> new ConcurrentHashMap<>());

for (final Entry<Integer, Long> partitionOffset : entry.getValue().entrySet()) {
final Integer partition = partitionOffset.getKey();
final Long offset = partitionOffset.getValue();
if (!partitionMap.containsKey(partition)
|| partitionMap.get(partition) < offset) {
partitionMap.put(partition, offset);
}
withComponent(topic, partition, offset);
}
}
return this;
Expand Down
127 changes: 127 additions & 0 deletions streams/src/test/java/org/apache/kafka/streams/query/PositionTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,11 +19,21 @@

import org.junit.jupiter.api.Test;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.Set;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import static org.apache.kafka.common.utils.Utils.mkEntry;
import static org.apache.kafka.common.utils.Utils.mkMap;
Expand All @@ -32,9 +42,12 @@
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;

public class PositionTest {

private static final Random RANDOM = new Random();

@Test
public void shouldCreateFromMap() {
final Map<String, Map<Integer, Long>> map = mkMap(
Expand Down Expand Up @@ -221,4 +234,118 @@ public void shouldNotHash() {
final HashMap<Position, Integer> map = new HashMap<>();
assertThrows(UnsupportedOperationException.class, () -> map.put(position, 5));
}

@Test
public void shouldMonotonicallyIncreasePartitionPosition() throws InterruptedException, ExecutionException, TimeoutException {
final int threadCount = 10;
final int maxTopics = 50;
final int maxPartitions = 50;
final int maxOffset = 1000;
final CountDownLatch startLatch = new CountDownLatch(threadCount);
final Position mergePosition = Position.emptyPosition();
final Position withComponentPosition = Position.emptyPosition();
final List<Future<?>> futures = new ArrayList<>();
ExecutorService executorService = null;

try {
executorService = Executors.newFixedThreadPool(threadCount);

for (int i = 0; i < threadCount; i++) {
futures.add(executorService.submit(() -> {
final Position threadPosition = Position.emptyPosition();
final int topicCount = RANDOM.nextInt(maxTopics) + 1;

// build the thread's position
for (int topicNum = 0; topicNum < topicCount; topicNum++) {
final String topic = "topic-" + topicNum;
final int partitionCount = RANDOM.nextInt(maxPartitions) + 1;
for (int partitionNum = 0; partitionNum < partitionCount; partitionNum++) {
final long offset = RANDOM.nextInt(maxOffset) + 1;
threadPosition.withComponent(topic, partitionNum, offset);
}
}

startLatch.countDown();
try {
startLatch.await();
} catch (final InterruptedException e) {
// convert to unchecked exception so the future completes exceptionally and fails the test
throw new RuntimeException(e);
}

// merge with the shared position
mergePosition.merge(threadPosition);
// duplicate the shared position to get a snapshot of its state
final Position threadMergePositionState = mergePosition.copy();

// update the shared position using withComponent
for (final String topic : threadPosition.getTopics()) {
for (final Map.Entry<Integer, Long> partitionOffset : threadPosition
.getPartitionPositions(topic)
.entrySet()) {
withComponentPosition.withComponent(topic, partitionOffset.getKey(), partitionOffset.getValue());
}
}
// duplicate the shared position to get a snapshot of its state
final Position threadWithComponentPositionState = withComponentPosition.copy();

// validate that any offsets in the merged position and the withComponent position are >= the thread position
for (final String topic : threadPosition.getTopics()) {
final Map<Integer, Long> threadOffsets = threadPosition.getPartitionPositions(topic);
final Map<Integer, Long> mergedOffsets = threadMergePositionState.getPartitionPositions(topic);
final Map<Integer, Long> withComponentOffsets = threadWithComponentPositionState.getPartitionPositions(topic);

for (final Map.Entry<Integer, Long> threadOffset : threadOffsets.entrySet()) {
final int partition = threadOffset.getKey();
final long offsetValue = threadOffset.getValue();

// merge checks
assertTrue(
mergedOffsets.containsKey(partition),
"merge method failure. Missing partition " + partition + " for topic " + topic
);
assertTrue(
mergedOffsets.get(partition) >= offsetValue,
"merge method failure. Offset for topic " +
topic +
" partition " +
partition +
" expected >= " +
offsetValue +
" but got " +
mergedOffsets.get(partition)
);

// withComponent checks
assertTrue(
withComponentOffsets.containsKey(partition),
"withComponent method failure. Missing partition " + partition + " for topic " + topic
);
assertTrue(
withComponentOffsets.get(partition) >= offsetValue,
"withComponent method failure. Offset for topic " +
topic +
" partition " +
partition +
" expected >= " +
offsetValue +
" but got " +
withComponentOffsets.get(partition)
);
}
}
}));
}

for (final Future<?> future : futures) {
// Wait for all threads to complete
future.get(1, TimeUnit.SECONDS); // Check for exceptions
}
} finally {
if (executorService != null) {
executorService.shutdown();
assertTrue(executorService.awaitTermination(10, TimeUnit.SECONDS));
}
}
}
}