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https://issues.apache.org/jira/browse/FLINK-5667?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15842420#comment-15842420
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Ufuk Celebi commented on FLINK-5667:
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Very god catch! :-)
> Possible state data loss when task fails while checkpointing
> ------------------------------------------------------------
>
> Key: FLINK-5667
> URL: https://issues.apache.org/jira/browse/FLINK-5667
> Project: Flink
> Issue Type: Bug
> Components: State Backends, Checkpointing
> Affects Versions: 1.2.0, 1.3.0
> Reporter: Till Rohrmann
> Assignee: Till Rohrmann
> Priority: Blocker
> Fix For: 1.2.0, 1.3.0
>
>
> It is possible that Flink loses state data when a {{Task}} fails while a
> checkpoint is being drawn. The scenario is the following:
> Flink has finished the synchronous checkpointing part and starts the
> asynchronous part by creating and submitting a {{AsyncCheckpointRunnable}} to
> an {{Executor}}. This runnable is also registered at the closeable registry.
> If the {{Task}} now fails before the {{AsyncCheckpointRunnable}} has
> completed, it will be closed due to being registered in the closeable
> registry. The closing operation will discard all state handles and cancel all
> runnable state futures. However, it will not stop the runnable from sending
> an acknowledge message to the {{CheckpointCoordinator}}.
> If this message completes the pending checkpoint, then this checkpoint will
> be transformed into a {{CompletedCheckpoint}} which is faulty (some of the
> data has already been deleted). Depending on Flink's configuration, this will
> discard older completed checkpoints and thus we will have state data loss.
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