log-backup: set checkpoint-ts - 1 as safe-point-ts

[joccau]

Signed-off-by: joccau zak.zhao@pingcap.com

What problem does this PR solve?

Issue Number: close #38250

Problem Summary:

• Failed to pause a log-backup task with the error BR:Backup:ErrBackupGCSafepointExceeded

What is changed and how it works?

Check List

Tests

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

Manual test

• Create log-backup task with a large workload. And the checkpoint lag > 30 min
  

• The gcSafePoint-ts is keeping smaller than checkpoint-ts
  
  

• Pause the log-backup task successfully.
  

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.

Fix the issue that failed to pause a log-backup task with the error BR:Backup:ErrBackupGCSafepointExceeded

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• Leavrth

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[joccau]

/cc @YuJuncen @3pointer @Leavrth PTAL

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/cc @YuJuncen @3pointer @Leavrth PTAL

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[joccau]

/component br

[joccau]

/merge

[ti-chi-bot]

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

Commit hash: 1beb13b

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #38644.

[sre-bot]

TiDB MergeCI notify

✅ Well Done! New fixed [1] after this pr merged.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-ddl-test	🔴 failed 1, success 5, total 6	30 min	Existing failure
idc-jenkins-ci-tidb/tics-test	✅ all 1 tests passed	6 min 25 sec	Fixed
idc-jenkins-ci/integration-cdc-test	🟢 all 38 tests passed	20 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 11 tests passed	10 min	Existing passed
idc-jenkins-ci-tidb/integration-common-test	🟢 all 17 tests passed	10 min	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	6 min 46 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	3 min 54 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 4 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	2 min 44 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed