[FLINK-15455][network] Enabled tcp connection reuse across multi jobs.

[KarmaGYZ]

What is the purpose of the change

Enabled tcp connection reuse across multi jobs.

Verifying this change

This change added tests and can be verified as follows:

• NettyPartitionRequestClientTest#testPartitionRequestClientReuse

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[KarmaGYZ]

cc @xintongsong @wsry

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Automated Checks

Last check on commit 4ef0a82 (Thu Jan 20 09:13:18 UTC 2022)

Warnings:

• No documentation files were touched! Remember to keep the Flink docs up to date!

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Review Progress

• ❓ 1. The [description] looks good.
• ❓ 2. There is [consensus] that the contribution should go into to Flink.
• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

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CI report:

• 45a1c20 Azure: SUCCESS

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[xintongsong]

Thanks @KarmaGYZ. I've went through the production codes and have some comments mostly concerning the code complexity and readability. I'd prefer to look into the testing codes later, as they are likely to be changed while addressing these comments.

[KarmaGYZ]

Thanks for the review @xintongsong . PR updated.

[KarmaGYZ]

@xintongsong Thanks for the review. PR updated.

[xintongsong]

Thanks for addressing my comments, @KarmaGYZ. LGTM.

[KarmaGYZ]

@flinkbot run azure