[
https://issues.apache.org/jira/browse/FLINK-9349?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16486698#comment-16486698
]
ASF GitHub Bot commented on FLINK-9349:
---------------------------------------
Github user tzulitai commented on a diff in the pull request:
https://github.com/apache/flink/pull/6040#discussion_r190120134
--- Diff:
flink-connectors/flink-connector-kafka-base/src/test/java/org/apache/flink/streaming/connectors/kafka/internals/AbstractFetcherTest.java
---
@@ -390,6 +398,102 @@ public void
testPeriodicWatermarksWithNoSubscribedPartitionsShouldYieldNoWaterma
assertEquals(100,
sourceContext.getLatestWatermark().getTimestamp());
}
+ @Test
+ public void testConcurrentPartitionsDiscoveryAndLoopFetching() throws
Exception {
+ // test data
+ final KafkaTopicPartition testPartition = new
KafkaTopicPartition("test", 42);
+
+ final Map<KafkaTopicPartition, Long> testCommitData = new
HashMap<>();
+ testCommitData.put(testPartition, 11L);
+
+ // ----- create the test fetcher -----
+
+ @SuppressWarnings("unchecked")
+ SourceContext<String> sourceContext =
PowerMockito.mock(SourceContext.class);
+ Map<KafkaTopicPartition, Long> partitionsWithInitialOffsets =
+ Collections.singletonMap(testPartition,
KafkaTopicPartitionStateSentinel.GROUP_OFFSET);
+
+ final TestFetcher<String> fetcher = new TestFetcher<>(
+ sourceContext,
+ partitionsWithInitialOffsets,
+ null, /* periodic assigner */
+ null, /* punctuated assigner */
+ new TestProcessingTimeService(),
+ 10);
+
+ // ----- run the fetcher -----
+
+ final AtomicReference<Throwable> error = new
AtomicReference<>();
+ int fetchTasks = 5;
+ final CountDownLatch latch = new CountDownLatch(fetchTasks);
+ ExecutorService service =
Executors.newFixedThreadPool(fetchTasks + 1);
+
+ service.submit(new Thread("fetcher runner") {
+ @Override
+ public void run() {
+ try {
+ latch.await();
+ fetcher.runFetchLoop();
--- End diff --
So, IMO, the test should look something like this:
```
final OneShotLatch fetchLoopWaitLatch = new OneShotLatch();
final OneShotLatch stateIterationBlockLatch = new
OneShotLatch();
final TestFetcher<String> fetcher = new TestFetcher<>(
sourceContext,
partitionsWithInitialOffsets,
null, /* periodic assigner */
null, /* punctuated assigner */
new TestProcessingTimeService(),
10,
fetchLoopWaitLatch,
stateIterationBlockLatch);
// ----- run the fetcher -----
final CheckedThread checkedThread = new CheckedThread() {
@Override
public void go() throws Exception {
fetcher.runFetchLoop();
}
};
checkedThread.start();
// wait until state iteration begins before adding discovered
partitions
fetchLoopWaitLatch.await();
fetcher.addDiscoveredPartitions(Collections.singletonList(testPartition));
stateIterationBlockLatch.trigger();
checkedThread.sync();
```
> KafkaConnector Exception while fetching from multiple kafka topics
> -------------------------------------------------------------------
>
> Key: FLINK-9349
> URL: https://issues.apache.org/jira/browse/FLINK-9349
> Project: Flink
> Issue Type: Bug
> Components: Kafka Connector
> Affects Versions: 1.4.0, 1.5.0
> Reporter: Vishal Santoshi
> Assignee: Sergey Nuyanzin
> Priority: Critical
> Attachments: Flink9349Test.java
>
>
> ./flink-connectors/flink-connector-kafka-0.9/src/main/java/org/apache/flink/streaming/connectors/kafka/internal/Kafka09Fetcher.java
>
> It seems the List subscribedPartitionStates was being modified when
> runFetchLoop iterated the List.
> This can happen if, e.g., FlinkKafkaConsumer runs the following code
> concurrently:
> kafkaFetcher.addDiscoveredPartitions(discoveredPartitions);
>
> {code:java}
> java.util.ConcurrentModificationException
> at
> java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:966)
> at java.util.LinkedList$ListItr.next(LinkedList.java:888)
> at
> org.apache.flink.streaming.connectors.kafka.internal.Kafka09Fetcher.runFetchLoop(Kafka09Fetcher.java:134)
> {code}
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