ASF GitHub Bot commented on FLINK-9349:

GitHub user snuyanzin opened a pull request:


    [FLINK-9349][Kafka Connector] KafkaConnector Exception while fetching from 
multiple kafka topics

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    fix synchronization issue
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You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/snuyanzin/flink 

Alternatively you can review and apply these changes as the patch at:


To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #6040
commit 8de5f37549607460659e171f9c3b48d0090383c0
Author: snuyanzin <snuyanzin@...>
Date:   2018-05-17T16:12:04Z

    added test and fix for FLINK-9349 by usage of CopyOnWriteArrayList

commit eee524e2d2a86af5252ed939000c12a2604917e9
Author: snuyanzin <snuyanzin@...>
Date:   2018-05-17T16:35:10Z

    fix checkstyle


> 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
>            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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