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https://issues.apache.org/jira/browse/FLINK-17860?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17113856#comment-17113856
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Roman Khachatryan commented on FLINK-17860:
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I think FLINK-13856 describes a more general problem (any state handle types).
This issue is about channel state handles only. They are:
* always located on file system (so we don't miss anything by replacing
discard() call with recursive delete)
* their number depends on stream properties (backpressure), not operator logic
* not incremental
> Recursively remove channel state directories
> --------------------------------------------
>
> Key: FLINK-17860
> URL: https://issues.apache.org/jira/browse/FLINK-17860
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / Checkpointing
> Affects Versions: 1.11.0
> Reporter: Roman Khachatryan
> Assignee: Roman Khachatryan
> Priority: Critical
> Fix For: 1.11.0
>
>
> With a high degree of parallelism, we end up with n*s number of files in each
> checkpoint (n = parallelism, s = stages). Writing them if fast (from many
> subtasks), removing them is slow (from JM).
> This can't be mitigated by state.backend.fs.memory-threshold because most
> states are ten to hundreds Mb.
>
> Instead of going through them 1 by 1, we could remove the directory
> recursively.
>
> The easiest way is to remove channelStateHandle.discard() calls and use
> isRecursive=true in
> FsCompletedCheckpointStorageLocation.disposeStorageLocation.
> Note: with the current isRecursive=false there will be an exception if there
> are any files left under that folder.
>
> This can be extended to other state handles in future as well.
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