lightning: split and scatter regions in batches (#33625)

[ti-srebot]

cherry-pick #33625 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/34258

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

git push [email protected]:ti-srebot/tidb.git pr/34258:release-5.4-2f2fa06c2fa5

---

What problem does this PR solve?

Issue Number: close #33618

Problem Summary:

Region scatter may timeout when split and scatter many regions at a time.

What is changed and how it works?

Add a batch limit for split and scatter regions. In a batch, lightning processes up to 4096 ranges. After all ranges in batch have been processed completely, lightning can process the next batch.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

I prepared about 1.8T data for a table which contains only one clustered primary key. TiDB cluster have ten TiKV nodes, each node have 200% cpu limit and 16GiB memory limit. Then I used lightning to import these data to TiDB cluster and observed the scatter operator status in grafana dashboard. To reproduce huge amount of regions, I set region-split-size to 8MiB. Finally, about 260k regions were created.

Master

Many scatter operator is timeout.

This PR

There is no operator timeout after this PR.

• No code

Release note

lightning: split and scatter regions in batches

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• D3Hunter
• lichunzhu

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[ti-srebot]

/run-all-tests

[ti-srebot]

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

[lichunzhu]

LGTM

[sleepymole]

/merge

[ti-chi-bot]

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

Commit hash: b2449a1

[sleepymole]

/merge

[ti-chi-bot]

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

Commit hash: dafee54

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/dafee545eb4c1a50c384efb5c0a6e13b6e4926a5