br: fix flaky test br_txn

[Tristan1900]

What problem does this PR solve?

Issue Number: close #54979

Problem Summary:

What changed and how does it work?

Feels like the way of generating load might have a race condition with the test setup. We noticed a mismatch of number of items before and after restore causing checksum mismatch.

This PR changes the code to generate a fixed number of items and run locally several times and cannot reproduce the issue anymore.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[tiprow]

Hi @Tristan1900. Thanks for your PR.

PRs from untrusted users cannot be marked as trusted with /ok-to-test in this repo meaning untrusted PR authors can never trigger tests themselves. Collaborators can still trigger tests on the PR using /test all.

I understand the commands that are listed here.

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 kubernetes-sigs/prow repository.

[Tristan1900]

/ok-to-test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.2355%. Comparing base (74034d4) to head (76097f7).
Report is 45 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #56444        +/-   ##
================================================
+ Coverage   73.3650%   77.2355%   +3.8704%     
================================================
  Files          1624       1649        +25     
  Lines        448069     468361     +20292     
================================================
+ Hits         328726     361741     +33015     
+ Misses        99206      85083     -14123     
- Partials      20137      21537      +1400     

Flag	Coverage Δ
integration	53.5005% <100.0000%> (?)
unit	73.7180% <66.6666%> (+1.2544%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	52.9478% <ø> (ø)
parser	∅ <ø> (∅)
br	64.9364% <100.0000%> (+19.4234%)	⬆️

[3pointer]

I think https://github.com/pingcap/tidb/pull/53836/files#diff-68f7f6acdf8e5dcdce8961426562671295381eb7d9c36f1a9511cd5fd595e3c8R110 fix the br_txn test.

[Tristan1900]

@3pointer seems that PR was merged at least one month ago, I was able to constantly reproduce this issue last week on my laptop. I will retry again on master branch to verify

[Tristan1900]

@3pointer still very easy to reproduce on my local env, it almost fails every time. I check out to the master branch and build everything from scratch to do the verification.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 3pointer, Leavrth

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

The pull request process is described here

Needs approval from an approver in each of these files:

• br/OWNERS [3pointer,Leavrth]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-10-10 02:42:49.608548043 +0000 UTC m=+1100325.028761055: ☑️ agreed by 3pointer.
• 2024-10-11 01:09:35.512564358 +0000 UTC m=+1181130.932777370: ☑️ agreed by Leavrth.