fix bug in getProcessingTimesByStepCopy

[clmccart]

getProcessingTimesByStepCopy was not returning a copy. That and the lack of synchronization on the processingTimesByStep object was causing concurrent modification race conditions.

---

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
• Update CHANGES.md with noteworthy changes.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

See the Contributor Guide for more tips on how to make review process smoother.

To check the build health, please visit https://github.com/apache/beam/blob/master/.test-infra/BUILD_STATUS.md

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI or the workflows README to see a list of phrases to trigger workflows.

[github-actions]

Checks are failing. Will not request review until checks are succeeding. If you'd like to override that behavior, comment assign set of reviewers

[github-actions]

Assigning reviewers. If you would like to opt out of this review, comment assign to next reviewer:

R: @tvalentyn added as fallback since no labels match configuration

Available commands:

• stop reviewer notifications - opt out of the automated review tooling
• remind me after tests pass - tag the comment author after tests pass
• waiting on author - shift the attention set back to the author (any comment or push by the author will return the attention set to the reviewers)

The PR bot will only process comments in the main thread (not review comments).

[arunpandianp]

Please annotate activeMessageMetadata and processingTimesByStep with @GuardedBy("this") to indicate that they are guarded by a synchronizing on this.

[tvalentyn]

R: @scwhittle

[tvalentyn]

waiting on author

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control

[arunpandianp]

LGTM except for the redundant synchronized block

[clmccart]

LGTM except for the redundant synchronized block

are you talking about the sync block on line 323?

[arunpandianp]

LGTM except for the redundant synchronized block

are you talking about the sync block on line 323?

No, recordActiveMessageInProcessingTimesMap is synchronized and there is also a synchronized block inside which is redundant.

[clmccart]

LGTM except for the redundant synchronized block

are you talking about the sync block on line 323?

No, recordActiveMessageInProcessingTimesMap is synchronized and there is also a synchronized block inside which is redundant.

i think that is necessary cause compute spins off a new thread. if i remove it, the guardedby annotation complains

[arunpandianp]

LGTM except for the redundant synchronized block

are you talking about the sync block on line 323?

No, recordActiveMessageInProcessingTimesMap is synchronized and there is also a synchronized block inside which is redundant.

i think that is necessary cause compute spins off a new thread. if i remove it, the guardedby annotation complains

processingTimesByStep is a HashMap, HashMap::compute executes the passed in function inline on the same thread.
ref: https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#compute-K-java.util.function.BiFunction-