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https://issues.apache.org/jira/browse/FLINK-40202?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18097798#comment-18097798
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YangyangHu commented on FLINK-40202:
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Please assign this to me, thanks!
> HybridSplitAssigner may initialize enumerator metrics concurrently with
> snapshot split assignment
> -------------------------------------------------------------------------------------------------
>
> Key: FLINK-40202
> URL: https://issues.apache.org/jira/browse/FLINK-40202
> Project: Flink
> Issue Type: Bug
> Components: Flink CDC
> Affects Versions: cdc-3.5.0
> Reporter: Hongshun Wang
> Priority: Major
> Fix For: cdc-3.6.0
>
>
> h3. Problem
> {{The issue has been observed with the following exception:}}
>
> {code:java}
> java.util.ConcurrentModificationException: null
> at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1043)
> ~[?:?]
> at java.util.ArrayList$Itr.next(ArrayList.java:997) ~[?:?]
> at
> org.apache.flink.cdc.connectors.base.source.assigner.SnapshotSplitAssigner.initEnumeratorMetrics(SnapshotSplitAssigner.java:305)
>
> ~[ververica-connector-sqlserver-1.20-vvr-11.7.0-4-jdk11-jar-with-dependencies.jar:1.20-vvr-11.7.0-4-jdk11]
> {code}
> {{}}
>
> h3. *Root Cause*
> h3. HybridSplitAssigner#open
> {code:java}
> snapshotSplitAssigner.open();
> // init enumerator metrics
> snapshotSplitAssigner.initEnumeratorMetrics(enumeratorMetrics); {code}
> {{SnapshotSplitAssigner#open}}
>
> {code:java}
> chunkSplitter.open();
> discoveryCaptureTables();
> captureNewlyAddedTables();
> startAsynchronouslySplit(); {code}
> {{}}
>
> # `SnapshotSplitAssigner#open` starts asynchronous snapshot splitting via
> `startAsynchronouslySplit()`.
> # enumerator metrics are initialized only after
> `snapshotSplitAssigner.open()` returns.
> # This leaves a race window where the background splitting thread can mutate
> split state while `initEnumeratorMetrics()` is traversing it.
> In the observed failure, the concurrent modification happens while iterating
> an `ArrayList`, resulting in `ConcurrentModificationException`.
> h3. {{}}
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