coordinator: Support resume successfully when status have previous errors

[hongyunyan]

What problem does this PR solve?

Issue Number: close #3953

What is changed and how it works?

This pull request significantly enhances the robustness of changefeed resume operations within the coordinator. It addresses a critical issue where changefeeds might fail to restart or immediately re-enter a problematic state due to lingering error information or an improperly initialized backoff mechanism from prior failures. By ensuring that resume attempts start with a clean, error-free status and a correctly reset internal state, the changes aim to provide a more reliable and predictable user experience for managing changefeeds.

Highlights

• Improved Changefeed Resume Logic: Changefeeds can now be successfully resumed even if their status previously contained errors. The system will no longer be blocked by stale error states during a resume operation.
• Error-Free Status for Resume: A new method, GetStatusForResume, has been introduced which provides a deep copy of the changefeed status but explicitly excludes any historical running errors, ensuring a clean state for resume attempts.
• Backoff Mechanism Reset: When a changefeed is resumed, its internal backoff mechanism is now properly reset. This includes updating the checkpoint baseline and clearing any in-progress restarting markers, preventing the changefeed from being immediately flagged as 'stuck' based on its previous failed state.
• Enhanced Test Coverage: New unit and integration tests have been added to validate that changefeeds can resume correctly despite stale errors and that the backoff checkpoint baseline is reset as expected.

Check List

Tests

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

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

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[gemini-code-assist]

Summary of Changes

Hello @hongyunyan, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the robustness of changefeed resume operations within the coordinator. It addresses a critical issue where changefeeds might fail to restart or immediately re-enter a problematic state due to lingering error information or an improperly initialized backoff mechanism from prior failures. By ensuring that resume attempts start with a clean, error-free status and a correctly reset internal state, the changes aim to provide a more reliable and predictable user experience for managing changefeeds.

Highlights

• Improved Changefeed Resume Logic: Changefeeds can now be successfully resumed even if their status previously contained errors. The system will no longer be blocked by stale error states during a resume operation.
• Error-Free Status for Resume: A new method, GetStatusForResume, has been introduced which provides a deep copy of the changefeed status but explicitly excludes any historical running errors, ensuring a clean state for resume attempts.
• Backoff Mechanism Reset: When a changefeed is resumed, its internal backoff mechanism is now properly reset. This includes updating the checkpoint baseline and clearing any in-progress restarting markers, preventing the changefeed from being immediately flagged as 'stuck' based on its previous failed state.
• Enhanced Test Coverage: New unit and integration tests have been added to validate that changefeeds can resume correctly despite stale errors and that the backoff checkpoint baseline is reset as expected.

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[gemini-code-assist]

Code Review

This pull request aims to allow changefeeds to resume successfully even if they have previous errors in their status. The changes correctly implement this by creating a new function GetStatusForResume that provides a clean status without old errors. Additionally, there are good improvements in GC safepoint handling on resume failure and in resetting the backoff logic to prevent incorrect "stuck" state detection. However, I've found a critical issue where the checkpoint timestamp is not correctly updated when resuming a changefeed, which could lead to the changefeed starting from an incorrect position.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 3AceShowHand, wk989898

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Details

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• OWNERS [3AceShowHand,wk989898]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-01-12 07:27:56.862168329 +0000 UTC m=+256120.924033238: ☑️ agreed by 3AceShowHand.
• 2026-01-12 08:01:13.824145416 +0000 UTC m=+258117.886010326: ☑️ agreed by wk989898.