logSink: revert defaultBufferChanSize, add a trigger to flush logSink.units when chennal is full (#2431)

[ti-chi-bot]

This is an automated cherry-pick of #2431

What problem does this PR solve?

1259 2424

What is changed and how it works?

Recover defaultBufferChanSize to 20480 which increased by 1469.

Add a criterion for refreshing logSink.units, which sendEvents.Load() == defaultBufferChanSize, i.e. units chennal is full.

Check List

Tests

• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has exported function/method change
• Has exported variable/fields change

Side effects

• Possible performance regression
• Increased code complexity

Related changes

• Need to cherry-pick to the release branch

Release note

fix a bug where synchronizing large tables to cdclog failed.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has not been approved.

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[amyangfei]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 08cf63d

[ti-chi-bot]

@ti-chi-bot: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[amyangfei]

/run-integration-tests

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (release-5.0@cd8c147). Click here to learn what that means.
The diff coverage is n/a.

@@               Coverage Diff                @@
##             release-5.0      #2445   +/-   ##
================================================
  Coverage               ?   55.4043%           
================================================
  Files                  ?        164           
  Lines                  ?      19540           
  Branches               ?          0           
================================================
  Hits                   ?      10826           
  Misses                 ?       7685           
  Partials               ?       1029