[jira] [Commented] (FLINK-40202) HybridSplitAssigner may initialize enumerator metrics concurrently with snapshot split assignment

["YangyangHu (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-40202?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18097798#comment-18097798 ] 

YangyangHu commented on FLINK-40202:
------------------------------------

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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