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https://issues.apache.org/jira/browse/BEAM-13667?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17497551#comment-17497551
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Beam JIRA Bot commented on BEAM-13667:
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This issue is assigned but has not received an update in 30 days so it has been
labeled "stale-assigned". If you are still working on the issue, please give an
update and remove the label. If you are no longer working on the issue, please
unassign so someone else may work on it. In 7 days the issue will be
automatically unassigned.
> 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
> Assignee: Sandeep Kathula
> Priority: P2
> Labels: stale-assigned
>
> 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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