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https://issues.apache.org/jira/browse/FLINK-26803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17729166#comment-17729166
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Dong Lin commented on FLINK-26803:
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[~fanrui] I see. Thanks for the information. The API change introduced in this
PR seems small. Still, it is probably good to always have a FLIP approved for
any addition/update of public evolving API in the future.
> Merge small ChannelState file for Unaligned Checkpoint
> ------------------------------------------------------
>
> Key: FLINK-26803
> URL: https://issues.apache.org/jira/browse/FLINK-26803
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / Checkpointing, Runtime / Network
> Reporter: Rui Fan
> Assignee: Rui Fan
> Priority: Major
> Labels: pull-request-available, stale-assigned
> Fix For: 1.17.0
>
> Attachments: image-2022-05-05-12-36-09-969.png
>
>
> When making an unaligned checkpoint, the number of ChannelState files is
> TaskNumber * subtaskNumber. For high parallelism job, it writes too many
> small files. It causes high load for hdfs NN.
>
> In our production, a job writes more than 50K small files for each Unaligned
> Checkpoint. Could we merge these files before write FileSystem? We can
> configure the maximum number of files each TM can write in a single Unaligned
> Checkpoint.
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