[FLINK-11707][network] Make InputGate extend AutoCloseable

[zhijiangW]

What is the purpose of the change

This is a sub-task for refactoring the interface of InputGate which would be created by ShuffleService future. So it is reasonable to reference with general InputGate anywhere instead of specific SingleInputGate.

To make InputGate extend AutoCloseable interface, the TaskCanceler could call InputGate#close instead of SingleInputGate#releaseAllResources.

Next we can further remove the reference with SingleInputGate in Task class by refactoring the updatePartitionInfo into NetworkEnvironment.

Brief change log

• Make InputGate extend AutoCloseable interface
• Change to reference with InputGate in TaskCanceler
• Rename releaseAllResources into close in ResultPartition

Verifying this change

This change is already covered by existing tests, such as SingleInputGateTest.

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, Yarn/Mesos, 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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[azagrebin]

Thanks for opening the PR @zhijiangW !
I think it looks good, I left only one comment to discuss.

[azagrebin]

UnionInputGate looks like something core Flink specific, some artificial abstraction, not related to ShuffleService.
At the moment, it is virtual and does not have real resources behind.
I would not even call it InputGate from shuffle service perspective, it is rather a partial decorator.
The real gates are managed by Task, one level down of abstraction.
Although, this close implementation looks logical, currently, it is not used.
My concern is that if we leave it, it might confuse in future: somebody might start calling it and break the lifecycle of real gates managed only by Task atm. As it is just a refactoring, I would leave this close method empty then, because it looks like it is not supposed to be used anyways.
or you think, there is another reason to have it like this?

[zhijiangW]

Yes, I totally agree with you above points. Thanks for kindly reminder!

[zhijiangW]

@azagrebin , thanks for the reviews! I agree with you above comments and submit a fixup commit for addressing it.

[azagrebin]

Thanks for addressing the comment @zhijiangW ! LGTM 👍