[jira] [Created] (FLINK-17674) OperatorCoordinator state in checkpoints should always be a ByteStreamStateHandle

[Shang Yuanchun (Jira)]

Stephan Ewen created FLINK-17674:
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             Summary: OperatorCoordinator state in checkpoints should always be a ByteStreamStateHandle
                 Key: FLINK-17674
                 URL: https://issues.apache.org/jira/browse/FLINK-17674
             Project: Flink
          Issue Type: Bug
          Components: Runtime / Checkpointing
            Reporter: Stephan Ewen
            Assignee: Stephan Ewen
             Fix For: 1.11.0


State restore to the task vertices and coordinators (even after loading the Checkpoint Metadata) happens in the JobManager's main thread and must consequently not do any potentially blocking I/O operations.

The OperatorCoordinator state is a generic {{StreamStateHandle}} whose state might require I/O to retrieve. This never happens in the current implementation (we always use {{ByteStreamStateHandle}}) the signatures and contracts don't guarantee that and leave this open for a potential future bug.

Typing the OperatorCoordinator state to ByteStreamStateHandle makes sure that we can always retrieve the data directly without I/O and clarifies that no arbitrary StreamStateHandle is supported at that point.

If state restoring becomes an asynchronous operation we can relax this restriction.



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