[FLINK-24741]Deprecate FileRecordFormat

[JingGe]

What is the purpose of the change

The FileRecordFormat and StreamFormat have too much commons. This makes user confused. The main motivation for removing it is the inherent design flaw in the batching of FileRecordFormat: StreamFormat can guarantee that only a certain amount of memory is being used (unless a single record exceeds that already), but FileRecordFormat can only batch by the number of records. By removing FileRecordFormat, we relay the responsibility of implementing the batching to the format developer; they need to use BulkFormat and find a better way than batch by number of records.

Brief change log

• marked FileRecordFormat and FileRecordFormatAdapter as @deprecated.
• refactored the relevant usages.
• updated javadoc.

Verifying this change

This change only marked some classes as deprecated and update relevant comments without any test coverage.

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)

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Automated Checks

Last check on commit 377613c (Wed Nov 03 08:38:35 UTC 2021)

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CI report:

• 82a491e Azure: SUCCESS

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[fapaul]

Thanks for working on this effort. I will definitely, help future format developers to have an easier time when trying to choose the right interface.

I agree with @slinkydeveloper that the @deprecated keyword should be used inside the docstrings.

[JingGe]

fixed all issues, @AHeise would you please help merging the PR, thanks.

[fapaul]

Thanks for the changes the code looks good to me now, only one nitty suggestion.

[fapaul]

Nit: I guess this hint is not entirely correct because users cannot use the StreamFormatAdapter without migrating to StreamFormat. In general, I am not sure whether it is strictly necessary to deprecate internal classes.

[AHeise]

I'd go for internal classes as well so that we will not forget to remove them when we remove the public class. Ofc, the link to StreamFormatAdapter is debatable but I also don't see that it's hurting anyone.

[AHeise]

@flinkbot run azure

[AHeise]

LGTM. Thanks!