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https://issues.apache.org/jira/browse/FLINK-9349?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16479388#comment-16479388
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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_r189029077
--- Diff:
flink-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/connectors/kafka/internals/AbstractFetcher.java
---
@@ -507,7 +507,7 @@ private void updateMinPunctuatedWatermark(Watermark
nextWatermark) {
SerializedValue<AssignerWithPunctuatedWatermarks<T>>
watermarksPunctuated,
ClassLoader userCodeClassLoader) throws IOException,
ClassNotFoundException {
- List<KafkaTopicPartitionState<KPH>> partitionStates = new
LinkedList<>();
+ List<KafkaTopicPartitionState<KPH>> partitionStates = new
CopyOnWriteArrayList<>();
--- End diff --
Would be nice to have a comment on why we need to use a
`CopyOnWriteArrayList`
> 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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