redo: fix a bug in redo dispatcher

[wk989898]

What problem does this PR solve?

Issue Number: close #3761 close #3851

What is changed and how it works?

• Function Renaming: The function IsTableTriggerEventDispatcher has been consistently renamed to IsTableTriggerDispatcher across the codebase for improved clarity and conciseness.
• Redo Dispatcher Bug Fix: A potential null pointer dereference in the UpdateRedoMeta function of the redo dispatcher has been addressed by adding a check to ensure the TableTriggerRedoDispatcher exists before attempting to update its metadata.
• Grafana Dashboard Enhancement: Grafana dashboards have been updated to include event_type in the legend format for several dispatcher-related metrics, providing more granular monitoring.

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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[ti-chi-bot]

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[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 primarily focuses on improving code clarity and robustness within the dispatcher components, particularly concerning redo logs. It introduces a more concise naming convention for a key dispatcher function and patches a critical bug that could lead to panics when updating redo metadata. Additionally, it enhances the monitoring capabilities by refining Grafana dashboard legends to provide more detailed insights into event dispatcher counts and creation durations.

Highlights

• Function Renaming: The function IsTableTriggerEventDispatcher has been consistently renamed to IsTableTriggerDispatcher across the codebase for improved clarity and conciseness.
• Redo Dispatcher Bug Fix: A potential null pointer dereference in the UpdateRedoMeta function of the redo dispatcher has been addressed by adding a check to ensure the TableTriggerRedoDispatcher exists before attempting to update its metadata.
• Grafana Dashboard Enhancement: Grafana dashboards have been updated to include event_type in the legend format for several dispatcher-related metrics, providing more granular monitoring.

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[wk989898]

/test all

[gemini-code-assist]

Code Review

This pull request primarily consists of a refactoring that renames IsTableTriggerEventDispatcher to IsTableTriggerDispatcher for consistency, alongside a bug fix in the redo dispatcher logic. The fix corrects the function used for checking an existing table trigger redo dispatcher and moves the nil-check for this dispatcher to the caller. While this resolves an incorrect error log, removing the nil-check from the UpdateRedoMeta function itself could lead to panics if it's called from other locations in the future. I've included a critical comment to address this potential robustness issue. The updates to the Grafana dashboards to incorporate event_type in metrics are also noted and look good.

[gemini-code-assist]

Removing the nil check for GetTableTriggerRedoDispatcher() introduces a risk of a nil pointer dereference if this function is called from a context where the dispatcher might not exist. While the only current caller in helper.go now performs this check, it's safer to make this function robust against such panics to prevent potential issues in the future. I recommend restoring the nil check within this function for better defensiveness.

if dispatcher := e.GetTableTriggerRedoDispatcher(); dispatcher != nil {
	dispatcher.UpdateMeta(checkpointTs, resolvedTs)
}

[wk989898]

/test all

[wk989898]

/test pull-cdc-mysql-integration-heavy

[wk989898]

/test pull-cdc-mysql-integration-heavy

[wk989898]

/test pull-cdc-mysql-integration-heavy

[wk989898]

/test pull-cdc-mysql-integration-heavy

[wk989898]

/test pull-cdc-mysql-integration-heavy

[wk989898]

/test pull-cdc-mysql-integration-heavy

[wk989898]

/test pull-cdc-mysql-integration-heavy

[ti-chi-bot]

@wk989898: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-error-log-review	3216fc8	link	true	/test pull-error-log-review
pull-cdc-mysql-integration-heavy	3216fc8	link	true	/test pull-cdc-mysql-integration-heavy

Full PR test history. Your PR dashboard.

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