Piotr Nowojski created FLINK-17122:
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Summary: Support InputSelectable and BoundedMultiInput operators
with checkpointing
Key: FLINK-17122
URL: https://issues.apache.org/jira/browse/FLINK-17122
Project: Flink
Issue Type: Wish
Components: Runtime / Checkpointing, Runtime / Network
Affects Versions: 1.10.0, 1.9.2
Reporter: Piotr Nowojski
Currently when user defined some {{InputSelectable}} or {{BoundedMultiInput}}
operators, checkpointing is not supported. Main problem is the that combination
of {{InputSelectable}} and barrier alignment can lead to deadlocks (checkpoint
barrier stuck on not selected channel).
Problem could be somehow mitigated via unaligned checkpoints (FLINK-14551), but
not fully. Even with unaligned checkpoints, checkpoint barriers can be stuck in
the job graph if there is a {{flatMap}} operator (or non {{flatMap}} operator
but if records are spanning multiple buffers), blocked in the middle of
processing by some down stream input selection. In such case we are not able to
perform unaligned checkpoint.
Potential solution could be using persistent communication channels or
detecting before mentioned situations and avoid the dead lock by spilling
excess data.
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