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fix: Wait for Kafka lookup startup catch-up #19858

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b7a96bd
fix: Wait for Kafka lookup startup catch-up
sakshichitnis27 Aug 3, 2026
9454152
Wait for Kafka lookup worker before closing cache
sakshichitnis27 Aug 3, 2026
d7d6f3b
fix: Avoid blocking Kafka lookup startup timeout
sakshichitnis27 Aug 5, 2026
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58 changes: 47 additions & 11 deletions ...on-namespace/src/main/java/org/apache/druid/query/lookup/KafkaLookupExtractorFactory.java
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,7 @@
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.common.TopicPartition;
import org.apache.kafka.common.serialization.StringDeserializer;

import javax.annotation.Nonnull;
Expand All @@ -52,6 +53,7 @@
import java.util.Collections;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CountDownLatch;
Expand Down Expand Up @@ -176,14 +178,21 @@ public boolean start()
final ListenableFuture<?> future = executorService.submit(() -> {
final Consumer<String, String> consumer = getConsumer();
consumer.subscribe(Collections.singletonList(topic));
Map<TopicPartition, Long> startupEndOffsets = null;
try {
while (!executorService.isShutdown()) {
try {
if (executorService.isShutdown()) {
break;
}
final ConsumerRecords<String, String> records = consumer.poll(Duration.ofMillis(1000));
startingReads.countDown();
if (startingReads.getCount() > 0) {
final Set<TopicPartition> assignment = consumer.assignment();
if (!assignment.isEmpty()
&& (startupEndOffsets == null || !startupEndOffsets.keySet().equals(assignment))) {
startupEndOffsets = consumer.endOffsets(assignment);
}
}

for (final ConsumerRecord<String, String> record : records) {
final String key = record.key();
Expand All @@ -204,6 +213,11 @@ public boolean start()
doubleEventCount.incrementAndGet();
LOG.trace("Placed key[%s] val[%s]", key, message);
}
if (startingReads.getCount() > 0

@FrankChen021 FrankChen021 Aug 3, 2026

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[P2] Wait for the catch-up worker before disposing its cache

When a finite connectTimeout expires while this new catch-up loop is processing a backlog, start() calls future.cancel(true) and immediately cacheHandler.close(). Cancellation only interrupts the worker; the record loop has no interrupt check, so it can continue put/remove calls after close. With the off-heap cache manager, close deletes the underlying MapDB map, racing those writes against deletion. Coordinate worker termination, or move cache disposal into the worker's completion path, before closing the cache.

&& startupEndOffsets != null
&& hasReachedEndOffsets(consumer, startupEndOffsets)) {
startingReads.countDown();
}
}
catch (Exception e) {
LOG.error(e, "Error reading stream for topic [%s]", topic);
Expand Down Expand Up @@ -251,10 +265,8 @@ public void onFailure(Throwable t)
}
}
catch (InterruptedException | ExecutionException | TimeoutException e) {
executorService.shutdown();
future.cancel(true);
LOG.error(e, "Failed to start kafka extraction factory");
cacheHandler.close();
shutdownExecutorAndCloseCache();
return false;
}

Expand All @@ -272,13 +284,7 @@ public boolean close()
return !started.get();
}
started.set(false);
executorService.shutdown();

final ListenableFuture<?> future = this.future;
if (future != null) {
future.cancel(true);
}
cacheHandler.close();
shutdownExecutorAndCloseCache();
return true;
}
}
Expand Down Expand Up @@ -381,6 +387,36 @@ ListenableFuture<?> getFuture()
return future;
}

boolean awaitExecutorTermination(final long timeout, final TimeUnit unit) throws InterruptedException
{
return executorService.awaitTermination(timeout, unit);
}

private void shutdownExecutorAndCloseCache()
{
// The executor is single-threaded, so the cache is not closed until the Kafka worker stops using it.
executorService.execute(cacheHandler::close);
executorService.shutdown();

final ListenableFuture<?> future = this.future;
if (future != null) {
future.cancel(true);
}
}

private static boolean hasReachedEndOffsets(
final Consumer<String, String> consumer,
final Map<TopicPartition, Long> endOffsets
)
{
for (final Map.Entry<TopicPartition, Long> endOffset : endOffsets.entrySet()) {
if (consumer.position(endOffset.getKey()) < endOffset.getValue()) {
return false;
}
}
return true;
}

/**
* Check that the user has not set forbidden Kafka consumer props
*
Expand Down
163 changes: 140 additions & 23 deletions ...amespace/src/test/java/org/apache/druid/query/lookup/KafkaLookupExtractorFactoryTest.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -26,22 +26,31 @@
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Sets;
import com.google.common.primitives.Bytes;
import com.google.common.util.concurrent.Uninterruptibles;
import org.apache.druid.jackson.DefaultObjectMapper;
import org.apache.druid.java.util.common.IAE;
import org.apache.druid.java.util.common.concurrent.Execs;
import org.apache.druid.server.lookup.namespace.cache.MockNamespaceExtractionCacheManager;
import org.apache.druid.server.lookup.namespace.cache.NamespaceExtractionCacheManager;
import org.apache.kafka.clients.consumer.Consumer;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.MockConsumer;
import org.apache.kafka.clients.consumer.OffsetResetStrategy;
import org.apache.kafka.common.TopicPartition;
import org.easymock.EasyMock;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicLong;

public class KafkaLookupExtractorFactoryTest
Expand Down Expand Up @@ -75,6 +84,14 @@ public Object findInjectableValue(
});
}

private void verifyCacheManagerAfterExecutorTerminates(
final KafkaLookupExtractorFactory factory
) throws InterruptedException
{
Assert.assertTrue(factory.awaitExecutorTermination(10, TimeUnit.SECONDS));
EasyMock.verify(cacheManager);
}

@Test
public void testSimpleSerDe() throws Exception
{
Expand Down Expand Up @@ -245,9 +262,13 @@ public void testStopWithoutStart()
}

@Test
public void testStartStop()
public void testStartStop() throws InterruptedException
{
Consumer<String, String> kafkaConsumer = new MockConsumer<>(OffsetResetStrategy.EARLIEST);
final MockConsumer<String, String> kafkaConsumer = new MockConsumer<>("earliest");
final TopicPartition topicPartition = new TopicPartition(TOPIC, 0);
kafkaConsumer.updateBeginningOffsets(ImmutableMap.of(topicPartition, 0L));
kafkaConsumer.updateEndOffsets(ImmutableMap.of(topicPartition, 0L));
kafkaConsumer.schedulePollTask(() -> kafkaConsumer.rebalance(Collections.singletonList(topicPartition)));
EasyMock.replay(cacheManager);

final KafkaLookupExtractorFactory factory = new KafkaLookupExtractorFactory(
Expand All @@ -268,13 +289,96 @@ Consumer<String, String> getConsumer()
Assert.assertTrue(factory.start());
Assert.assertTrue(factory.close());
Assert.assertTrue(factory.getFuture().isDone());
EasyMock.verify(cacheManager);
verifyCacheManagerAfterExecutorTerminates(factory);
}

@Test
public void testStartWaitsForInitialEndOffsets() throws Exception
{
final MockConsumer<String, String> kafkaConsumer = new MockConsumer<>("earliest");
final TopicPartition topicPartition = new TopicPartition(TOPIC, 0);
final CountDownLatch firstPollComplete = new CountDownLatch(1);
final CountDownLatch allowCatchUp = new CountDownLatch(1);

kafkaConsumer.schedulePollTask(() -> {
kafkaConsumer.updateBeginningOffsets(ImmutableMap.of(topicPartition, 0L));
kafkaConsumer.updateEndOffsets(ImmutableMap.of(topicPartition, 2L));
kafkaConsumer.rebalance(Collections.singletonList(topicPartition));
kafkaConsumer.addRecord(new ConsumerRecord<>(TOPIC, 0, 0L, "key-0", "value-0"));
firstPollComplete.countDown();
});
kafkaConsumer.schedulePollTask(() -> {
try {
if (!allowCatchUp.await(10, TimeUnit.SECONDS)) {
throw new RuntimeException("Timed out waiting to finish the startup catch-up");
}
}
catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new RuntimeException(e);
}
kafkaConsumer.addRecord(new ConsumerRecord<>(TOPIC, 0, 1L, "key-1", "value-1"));
});

EasyMock.replay(cacheManager);
final KafkaLookupExtractorFactory factory = new KafkaLookupExtractorFactory(
cacheManager,
TOPIC,
ImmutableMap.of("bootstrap.servers", "localhost"),
10_000L,
false
)
{
@Override
Consumer<String, String> getConsumer()
{
return kafkaConsumer;
}
};
final ExecutorService startExecutor = Execs.singleThreaded("kafka-lookup-start-test");
final Future<Boolean> startFuture = startExecutor.submit(factory::start);

try {
Assert.assertTrue(firstPollComplete.await(10, TimeUnit.SECONDS));
Assert.assertThrows(
"start returned before the consumer reached its initial end offsets",
TimeoutException.class,
() -> startFuture.get(100, TimeUnit.MILLISECONDS)
);
allowCatchUp.countDown();
Assert.assertTrue(startFuture.get(10, TimeUnit.SECONDS));
Assert.assertEquals("value-0", factory.get().apply("key-0"));
Assert.assertEquals("value-1", factory.get().apply("key-1"));
}
finally {
allowCatchUp.countDown();
factory.close();
startExecutor.shutdownNow();
}
verifyCacheManagerAfterExecutorTerminates(factory);
}


@Test
public void testStartFailsFromTimeout()
public void testStartTimeoutReturnsBeforeConsumerStops() throws Exception
{
final CountDownLatch pollStarted = new CountDownLatch(1);
final CountDownLatch allowPollToFinish = new CountDownLatch(1);
final CountDownLatch consumerClosed = new CountDownLatch(1);
final MockConsumer<String, String> kafkaConsumer = new MockConsumer<>("earliest")
{
@Override
public synchronized void close()
{
super.close();
consumerClosed.countDown();
}
};
kafkaConsumer.schedulePollTask(() -> {
pollStarted.countDown();
Uninterruptibles.awaitUninterruptibly(allowPollToFinish);
});

EasyMock.replay(cacheManager);
final KafkaLookupExtractorFactory factory = new KafkaLookupExtractorFactory(
cacheManager,
Expand All @@ -285,28 +389,37 @@ public void testStartFailsFromTimeout()
)
{
@Override
Consumer getConsumer()
Consumer<String, String> getConsumer()
{
// Lock up
try {
Thread.currentThread().join();
}
catch (InterruptedException e) {
throw new RuntimeException(e);
}
throw new RuntimeException("shouldn't make it here");
return kafkaConsumer;
}
};
Assert.assertFalse(factory.start());
Assert.assertTrue(factory.getFuture().isDone());
Assert.assertTrue(factory.getFuture().isCancelled());
final ExecutorService startExecutor = Execs.singleThreaded("kafka-lookup-timeout-test");
final Future<Boolean> startFuture = startExecutor.submit(factory::start);

try {
Assert.assertTrue(pollStarted.await(10, TimeUnit.SECONDS));
Assert.assertFalse(startFuture.get(500, TimeUnit.MILLISECONDS));
Assert.assertEquals(1L, consumerClosed.getCount());
Assert.assertFalse(factory.awaitExecutorTermination(100, TimeUnit.MILLISECONDS));

allowPollToFinish.countDown();
Assert.assertTrue(consumerClosed.await(10, TimeUnit.SECONDS));
Assert.assertTrue(factory.awaitExecutorTermination(10, TimeUnit.SECONDS));
Assert.assertTrue(factory.getFuture().isDone());
Assert.assertTrue(factory.getFuture().isCancelled());
}
finally {
allowPollToFinish.countDown();
startExecutor.shutdownNow();
}
EasyMock.verify(cacheManager);
}

@Test
public void testStartStopStart()
public void testStartStopStart() throws InterruptedException
{
Consumer<String, String> kafkaConsumer = new MockConsumer<>(OffsetResetStrategy.EARLIEST);
Consumer<String, String> kafkaConsumer = new MockConsumer<>("earliest");
EasyMock.replay(cacheManager);
final KafkaLookupExtractorFactory factory = new KafkaLookupExtractorFactory(
cacheManager,
Expand All @@ -323,13 +436,17 @@ Consumer<String, String> getConsumer()
Assert.assertTrue(factory.start());
Assert.assertTrue(factory.close());
Assert.assertFalse(factory.start());
EasyMock.verify(cacheManager);
verifyCacheManagerAfterExecutorTerminates(factory);
}

@Test
public void testStartStartStopStop()
public void testStartStartStopStop() throws InterruptedException
{
Consumer<String, String> kafkaConsumer = new MockConsumer<>(OffsetResetStrategy.EARLIEST);
final MockConsumer<String, String> kafkaConsumer = new MockConsumer<>("earliest");
final TopicPartition topicPartition = new TopicPartition(TOPIC, 0);
kafkaConsumer.updateBeginningOffsets(ImmutableMap.of(topicPartition, 0L));
kafkaConsumer.updateEndOffsets(ImmutableMap.of(topicPartition, 0L));
kafkaConsumer.schedulePollTask(() -> kafkaConsumer.rebalance(Collections.singletonList(topicPartition)));
EasyMock.replay(cacheManager);
final KafkaLookupExtractorFactory factory = new KafkaLookupExtractorFactory(
cacheManager,
Expand All @@ -349,7 +466,7 @@ Consumer<String, String> getConsumer()
Assert.assertTrue(factory.start());
Assert.assertTrue(factory.close());
Assert.assertTrue(factory.close());
EasyMock.verify(cacheManager);
verifyCacheManagerAfterExecutorTerminates(factory);
}

@Test
Expand Down
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