scheduling: Prevent duplicate add operators by skipping split postFinish when target nodes mismatch

[hongyunyan]

What problem does this PR solve?

Issue Number: close #4077

What is changed and how it works?

This pull request addresses a potential issue in the scheduling mechanism where duplicate add operators could be created during a split operation if the provided target nodes do not align with the actual number of resulting spans. The changes ensure that the postFinish callback, which typically initiates further scheduling, is only invoked when the target nodes are correctly aligned. In cases of mismatch, the new spans are marked as absent, allowing the system's basic scheduler to take over and prevent redundant operations, thereby improving the robustness of the scheduling process.

Highlights

• Conditional postFinish execution: The SplitDispatcherOperator.PostFinish method now conditionally invokes its postFinish callback. This callback is only executed if the new replica sets are successfully placed into a scheduling state with aligned target nodes.
• ReplaceReplicaSet return value: The spanController.ReplaceReplicaSet function has been updated to return an additional boolean value, replicasInScheduling, which indicates whether the newly created replica sets were successfully assigned to the specified target nodes.
• Handling target node mismatch: If the number of splitTargetNodes does not match the number of newly created spans, ReplaceReplicaSet will now place these new spans into an "absent" state instead of a "scheduling" state. This allows the basic scheduler to handle them and prevents the creation of duplicate add operators.
• New test case: A new unit test, TestSplitOperator_PostFinishSkipsWhenTargetNodesMismatch, has been added to specifically verify the behavior where postFinish is skipped when target nodes do not align with the actual split results.

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 addresses a potential issue in the scheduling mechanism where duplicate add operators could be created during a split operation if the provided target nodes do not align with the actual number of resulting spans. The changes ensure that the postFinish callback, which typically initiates further scheduling, is only invoked when the target nodes are correctly aligned. In cases of mismatch, the new spans are marked as absent, allowing the system's basic scheduler to take over and prevent redundant operations, thereby improving the robustness of the scheduling process.

Highlights

• Conditional postFinish execution: The SplitDispatcherOperator.PostFinish method now conditionally invokes its postFinish callback. This callback is only executed if the new replica sets are successfully placed into a scheduling state with aligned target nodes.
• ReplaceReplicaSet return value: The spanController.ReplaceReplicaSet function has been updated to return an additional boolean value, replicasInScheduling, which indicates whether the newly created replica sets were successfully assigned to the specified target nodes.
• Handling target node mismatch: If the number of splitTargetNodes does not match the number of newly created spans, ReplaceReplicaSet will now place these new spans into an "absent" state instead of a "scheduling" state. This allows the basic scheduler to handle them and prevents the creation of duplicate add operators.
• New test case: A new unit test, TestSplitOperator_PostFinishSkipsWhenTargetNodesMismatch, has been added to specifically verify the behavior where postFinish is skipped when target nodes do not align with the actual split results.

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[gemini-code-assist]

Code Review

This pull request addresses a bug that could lead to a panic or race condition during a table span split operation when the number of target nodes mismatches the number of resulting spans. The fix is implemented by introducing a replicasInScheduling boolean flag returned by ReplaceReplicaSet. This flag indicates whether the new replicas have been placed in a scheduling state. The SplitDispatcherOperator now checks this flag before invoking the postFinish callback, effectively preventing duplicate scheduling operations. A warning log has also been added for cases where postFinish is skipped due to the mismatch. The changes are accompanied by a new unit test that specifically covers the fixed scenario, ensuring the bug is resolved and preventing future regressions. The implementation is clean, correct, and the added test provides good coverage for the fix.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: wk989898

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• OWNERS [wk989898]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-01-28 09:04:34.513099275 +0000 UTC m=+1175902.127056131: ☑️ agreed by wk989898.