lightning: use pd timestamp to update gc safepoint (#32734)

[ti-srebot]

cherry-pick #32734 to release-5.4
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/32799

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tidb.git pr/32799:release-5.4-5288efa20dc6

---

What problem does this PR solve?

Issue Number: close #32733

Problem Summary:

Lightning uses the local unix timestamp to update service gc safepoint. However, local clock is not reliable. If the start ts of checksum transaction is smaller than the local ts, lightning may encounter “GC life time is shorter than transaction duration” error during doing checksum.

What is changed and how it works?

Always use PD timestamp to update service gc safepoint.

Check List

Tests

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

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

lightning: fix checksum encountered “GC life time is shorter than transaction duration” error

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• D3Hunter
• gozssky

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[ti-srebot]

/run-all-tests

[ti-srebot]

@gozssky you're already a collaborator in bot's repo.

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/121e122ce87d4c072a12441045948d65d12d6d40

[sleepymole]

/merge

[ti-chi-bot]

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

Commit hash: 121e122

[hawkingrei]

/run-unit-test