[jira] [Commented] (FLINK-5086) Clean dead snapshot files produced by the tasks failing to acknowledge checkpoints

["Till Rohrmann (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-5086?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15767058#comment-15767058 ] 

Till Rohrmann commented on FLINK-5086:
--------------------------------------

Hi [~roman_maier], what's your plan to solve this problem?

> Clean dead snapshot files produced by the tasks failing to acknowledge checkpoints
> ----------------------------------------------------------------------------------
>
>                 Key: FLINK-5086
>                 URL: https://issues.apache.org/jira/browse/FLINK-5086
>             Project: Flink
>          Issue Type: Bug
>          Components: State Backends, Checkpointing
>            Reporter: Xiaogang Shi
>            Assignee: Roman Maier
>
> A task may fail when performing checkpoints. In that case, the task may have already copied some data to external storage. But since the task fails to send the state handler to {{CheckpointCoordinator}}, the copied data will not be deleted by {{CheckpointCoordinator}}. 
> I think we must find a method to clean such dead snapshot data to avoid unlimited usage of external storage. 
> One possible method is to clean these dead files when the task recovers. When a task recovers, {{CheckpointCoordinator}} will tell the task all the retained checkpoints. The task then can scan the external storage to delete all the  snapshots not in these retained checkpoints.



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