[FLINK-10441]Don't log warning when creating upload directory

[tianchen92]

What is the purpose of the change

This PR is related to FLINK-10441. RestServerEndpoint.createUploadDir(Path, Logger) logs a warning if the upload directory does not exist, it's better to log the creation of the web directory on INFO instead of the warning.

Brief change log

• log the creation of the web directory on INFO instead of the warning

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

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, Yarn/Mesos, 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)

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• ✅ 1. The [description] looks good.
  • Approved by @zentol [PMC]
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[tianchen92]

Hi @uce, could you please help review this PR? thanks

[zentol]

This is not the correct fix imo. So, the message is logged as WARN on purpose since we've had cases in the past where this directory was removed without a user realizing it.

The correct fix would be to log it on INFO only on the initial startup (at which point we expect the directory to not exist), but on WARN after that.

[uce]

I agree with @zentol.

[tianchen92]

@zentol @uce Thanks for your detailed comments, I have got your point. Is it right to add a param in createUploadDir to identify whether it‘s the initial startup, then we can decide log it on INFO level or Warning level?
I am just not sure how to confirm which is initial startup. Is createUploadDir invoked in RestServerEndpoint constructor the initial startup and others in FileUploadHandler not?
Thanks！

[zentol]

add a param in createUploadDir to identify whether it‘s the initial startup

yes.

createUploadDir invoked in RestServerEndpoint constructor [is] the initial startup and others in FileUploadHandler not

yes

[zentol]

@flinkbot approve-until architecture

[tianchen92]

Thanks for your reply @zentol, I have resolved the comments, please have a look.