AHeise opened a new pull request, #26433:
URL: https://github.com/apache/flink/pull/26433
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## What is the purpose of the change
So far, we used a special value for the final checkpoint on endInput.
However, as shown in the description of this ticket, final doesn't mean final.
Hence, multiple committables with EOI could be created at different times.
With this commit, we stop using a special value for such committables and
instead try to guess the checkpoint id of the next checkpoint. There are
various factors that influence the checkpoint id but we can mostly ignore them
all because we just need to pick a checkpoint id that is
- higher than all checkpoint ids of the previous, successful checkpoints of
this attempt
- higher than the checkpoint id of the restored checkpoint
- lower than any future checkpoint id.
Hence, we just remember the last observed checkpoint id (initialized with
max(0, restored id)), and use last id + 1 for endInput. Naturally, multiple
endInput calls happening through restarts will result in unique checkpoint ids.
Note that aborted checkpoints before endInput may result in diverged checkpoint
ids across subtasks. However, each of the id satisfies above requirements and
any id of endInput1 will be smaller than any id of endInput2. Thus, diverged
checkpoint ids will not impact correctness at all.
## Brief change log
- Clarify contract of endInput
- Infer checkpoint id on endInput
## Verifying this change
Covered by existing tests. No new tests since it removes special case
handling.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (yes / **no**)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (yes / **no**)
- The serializers: (yes / **no** / don't know)
- The runtime per-record code paths (performance sensitive): (yes / **no**
/ don't know)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (**yes** / no / don't
know)
- The S3 file system connector: (yes / **no** / don't know)
## Documentation
- Does this pull request introduce a new feature? (yes / **no**)
- If yes, how is the feature documented? (**not applicable** / docs /
JavaDocs / not documented)
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