[jira] [Commented] (FLINK-15132) Checkpoint Coordinator does Checkpoint I/O in JobMaster Main Thread

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

    [ https://issues.apache.org/jira/browse/FLINK-15132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16991100#comment-16991100 ] 

Yun Tang commented on FLINK-15132:
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Wondering whether this is a real blocker, {{CheckpointCoordinator#completePendingCheckpoint()}} included in {{CheckpointCoordinator#receiveAcknowledgeMessage()}}  is executed by [ioExecutor|https://github.com/apache/flink/blob/171020749f7fccfa7781563569e2c88ea5e8b6a1/flink-runtime/src/main/java/org/apache/flink/runtime/scheduler/SchedulerBase.java#L748], which is not the main thread of Scheduler or JobMaster.

> Checkpoint Coordinator does Checkpoint I/O in JobMaster Main Thread
> -------------------------------------------------------------------
>
>                 Key: FLINK-15132
>                 URL: https://issues.apache.org/jira/browse/FLINK-15132
>             Project: Flink
>          Issue Type: Bug
>          Components: Runtime / Checkpointing
>            Reporter: Stephan Ewen
>            Priority: Blocker
>             Fix For: 1.10.0
>
>
> The {{PendingCheckpoint.completePendingCheckpoint()}} method is called synchronously from within the Scheduler / JobMaster Main Thread.
> The method writes out the checkpoint metadata, which is a potentially blocking I/O method.
> Because the target may block arbitrarily long (for example S3 when load throttling), this can bring down the entire cluster (blocking actor threads, heartbeat timeouts).



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