sink(ticdc): fix a bug that may cause data loss while closing Writer failed

[wk989898]

What problem does this PR solve?

Issue Number: close #12436

What is changed and how it works?

In the previous implementation, the error of writer.Close was not handled, and some DMLs may upload failed.
This error should block the advance and cause the changefeed to finally restart.

Check List

Tests

• Unit test
• Integration test

Questions

Will it cause performance regression or break compatibility?

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

Release note

Fix a bug that may cause DML loss while failing to close the writer of the storage sink

[gemini-code-assist]

Summary of Changes

Hello @wk989898, 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 resolves a significant data integrity issue within the TiCDC cloud storage sink. Previously, failures encountered while closing a data writer were not propagated, potentially leading to silent data loss for DML operations. The change ensures that any error during the writer's closure is immediately caught and returned, thereby preventing data loss by halting the process and triggering a necessary changefeed restart to maintain consistency.

Highlights

• Data Loss Prevention: Addressed a critical bug where DML operations could be lost if the writer.Close operation failed within the cloud storage sink, as the error was not properly handled.
• Error Handling Improvement: Modified the writeDataFile function to explicitly handle errors from writer.Close. If closing the writer fails, an error is now immediately returned, which will block further advance and cause the changefeed to restart, preventing data inconsistency.

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[gemini-code-assist]

Code Review

The pull request effectively addresses the bug where writer.Close errors were not properly handled, potentially leading to data loss. By moving the writer.Close call out of the defer block and checking its return value immediately, the system now correctly propagates errors that occur during the writer's closing phase. This ensures that if a write operation succeeds but the subsequent close operation fails, the error is caught and handled, preventing silent data loss and allowing the changefeed to restart as intended. This is a critical fix for data integrity.

[wk989898]

/retest

[wk989898]

/check-issue-triage-complete

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-12-05 00:18:08.558911129 +0000 UTC m=+568233.372688701: ☑️ agreed by asddongmen.
• 2025-12-05 06:16:43.986505998 +0000 UTC m=+589748.800283560: ☑️ agreed by 3AceShowHand.

[ti-chi-bot]

@flowbehappy: adding LGTM is restricted to approvers and reviewers in OWNERS files.

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

The full list of commands accepted by this bot can be found here.

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Details

Needs approval from an approver in each of these files:

• OWNERS [3AceShowHand,asddongmen]

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[wk989898]

/retest

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #12439.
But this PR has conflicts, please resolve them!

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #12440.
But this PR has conflicts, please resolve them!

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #12441.
But this PR has conflicts, please resolve them!

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #12442.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #12443.