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https://issues.apache.org/jira/browse/BEAM-13667?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17531323#comment-17531323
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Beam JIRA Bot commented on BEAM-13667:
--------------------------------------
This issue is P2 but has been unassigned without any comment for 60 days so it
has been labeled "stale-P2". If this issue is still affecting you, we care!
Please comment and remove the label. Otherwise, in 14 days the issue will be
moved to P3.
Please see https://beam.apache.org/contribute/jira-priorities/ for a detailed
explanation of what these priorities mean.
> Users cannot provide their own sharding function when using FileIO
> ------------------------------------------------------------------
>
> Key: BEAM-13667
> URL: https://issues.apache.org/jira/browse/BEAM-13667
> Project: Beam
> Issue Type: Improvement
> Components: sdk-java-core
> Affects Versions: 2.35.0
> Reporter: Sandeep Kathula
> Priority: P2
> Labels: stale-P2
>
> Beam uses RandomShardingFunction
> ([https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/io/WriteFiles.java#L834])
> by default for sharding when using FileIO.write().
>
> RandomShardingFuncction doesn’t work well with Flink Runner. Its assigning
> same key (hashDestination(destination, destinationCoder)) along with the
> shard number.
> ([https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/io/WriteFiles.java#L863])
> This is causing different ShardedKeys going to same task slot. As a result,
> there is no equal distribution of files written from different task slots.
> E.g. 2 files are written by task slot 1, 3 files written by task slot 2, 0
> files written by other task slots.
>
> As a result, we are seeing Out of Memory from the pods writing more files.
>
> At
> [https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/io/WriteFiles.java#L695-L698]
> There is an option to give a different sharding function. But there is no way
> for the user to mention different sharding function when using FileIO class.
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