[BP-1.20] [FLINK-35657][runtime-web] use parseFloat for metric value

[showuon]

What is the purpose of the change

master branch PR: #24964.

Flink UI always shows float metric value as int/long. For example, outPoolUsage/inPoolUsage are always 0 or 1 at UI. That's not helpful when troubleshooting from UI.

After investigation, I found it's because we always parse the metric value via parseInt method. We should use parseFloat for it. The parseFloat can achieve what we expect because when the provided string is a integer, it'll also parsed as an integer, not float. Like this:

Before this change, the UI is displayed like this:

After this change, the UI can display float value like this:

Brief change log

Replacing parseInt with parseFloat to parse metric value.

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, 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

[showuon]

@hlteoh37 , PR to backport to 1.20. Thanks.

[flinkbot]

CI report:

• 8312634 Azure: SUCCESS

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