cdc: fix data race in TestGCAndCleanup by moving global variable modification to TestMain

[wlwilliamx]

What problem does this PR solve?

Issue Number: close #12371

What is changed and how it works?

This PR fixes a data race detected in the cdc/redo test suite.

Changes:

1. cdc/redo/meta_manager_test.go:

   • Removed the code block from TestGCAndCleanup that sets redo.DefaultGCIntervalInMs to 20 and defers its reset. This stops the global variable from being written to inside a parallel test.

2. cdc/redo/main_test.go:

   • Added the github.com/pingcap/tiflow/pkg/redo import.
   • Moved the logic to set redo.DefaultGCIntervalInMs = 20 into the TestMain function.
   • A defer statement is used in TestMain to restore the original value after all tests in the cdc/redo package have finished running.

By moving this logic to TestMain, the global variable is set once at the beginning of the entire package's test run, before any parallel tests are executed. This provides a stable test environment for all tests in the package while completely eliminating the data race.

Check List

Tests

• Unit test
• Integration test

Questions

Will it cause performance regression or break compatibility?

None

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

None

Release note

None

[ti-chi-bot[bot]]

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[gemini-code-assist[bot]]

Summary of Changes

Hello @wlwilliamx, I'm Gemini Code Assist[^1]! 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 data race issue identified in the cdc/redo test suite. The core of the fix involves centralizing the setup and teardown of a global configuration variable, redo.DefaultGCIntervalInMs, into the TestMain function. This ensures that the variable is initialized consistently and safely before any parallel tests run, thereby preventing race conditions and establishing a more stable and predictable testing environment for the package.

Highlights

• Data Race Fix: Addresses a data race detected in the cdc/redo test suite by ensuring the global variable redo.DefaultGCIntervalInMs is set once before any parallel tests are executed.
• Test Setup Refactor: Relocates the modification and restoration of the global variable redo.DefaultGCIntervalInMs from TestGCAndCleanup to the TestMain function within the cdc/redo package.

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[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lidezhu, wk989898

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[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2025-10-20 04:39:39.055744818 +0000 UTC m=+673885.132997377: :ballot_box_with_check: agreed by lidezhu.
• 2025-10-20 06:17:59.763665512 +0000 UTC m=+679785.840918062: :ballot_box_with_check: agreed by wk989898.