logservice: avoid dispatcher registration failure during schema store initialization

[lidezhu]

What problem does this PR solve?

Issue Number: ref #4272 close #4285

What is changed and how it works?

This pull request aims to avoid schema store registration failure like the following:

[2026/02/22 13:16:56.220 +08:00] [ERROR] [event_broker.go:983] ["register table to schemaStore failed"] [keyspaceID=1] [dispatcherID=31207855160892268629454174482575748278] [tableID=181] [startTs=464450330781810783] [span="tableID: 181, startKey: 7800000174800000ff00000000b55f7200fe, endKey: 7800000174800000ff00000000b55f7300fe, keyspaceID: 1"] [error="[CDC:ErrNewStore]new store failed: context canceled"]

Highlights

• Event Dispatcher Robustness: Enhanced the addDispatcher function to ensure proper unregistration and marking of dispatchers as removed immediately upon schema store registration failure, preventing inconsistent states.
• Improved CreateTiStore Retry Logic: Refactored the retry mechanism for CreateTiStore to differentiate between caller-initiated context cancellations (which should stop retries) and internal client cancellations (which should continue retries), improving resilience.
• Comprehensive Testing: Added new unit tests to validate the corrected addDispatcher error handling and the refined CreateTiStore retry behavior.
• Mock Event Store Enhancements: Updated the mock event store to accurately track unregistration calls and ensure complete cleanup of dispatcher mappings during tests.

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

Please refer to [Release Notes Language Style Guide](https://pingcap.github.io/tidb-dev-guide/contribute-to-tidb/release-notes-style-guide.html) to write a quality release note.

If you don't think this PR needs a release note then fill it with `None`.

Summary by CodeRabbit

• Bug Fixes

  • Ensures event dispatchers are properly marked and unregistered on schema registration failures to avoid stray dispatching.
  • Refines upstream connection retry handling to respect caller cancellation.
  • Ensures event store write batches are always released to prevent resource leaks.

• Tests

  • Added tests covering dispatcher unregistration on schema errors and retry cancellation behavior.

[gemini-code-assist]

Summary of Changes

Hello, 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 potential issues during service initialization and resource management. It improves the robustness of event dispatcher registration by ensuring immediate cleanup upon failure and refines the retry strategy for CreateTiStore to handle context cancellations more intelligently. These changes aim to prevent service registration failures and enhance the overall stability of the system.

Highlights

• Event Dispatcher Robustness: Enhanced the addDispatcher function to ensure proper unregistration and marking of dispatchers as removed immediately upon schema store registration failure, preventing inconsistent states.
• Improved CreateTiStore Retry Logic: Refactored the retry mechanism for CreateTiStore to differentiate between caller-initiated context cancellations (which should stop retries) and internal client cancellations (which should continue retries), improving resilience.
• Comprehensive Testing: Added new unit tests to validate the corrected addDispatcher error handling and the refined CreateTiStore retry behavior.
• Mock Event Store Enhancements: Updated the mock event store to accurately track unregistration calls and ensure complete cleanup of dispatcher mappings during tests.

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Changelog

• pkg/eventservice/event_broker.go
  • Added logic to mark a dispatcher as removed and unregister it from the event store immediately if addDispatcher fails due to a schema store error.
• pkg/eventservice/event_broker_test.go
  • Added TestAddDispatcherUnregisterOnSchemaStoreError to verify that dispatchers are correctly unregistered when schema store registration fails.
• pkg/eventservice/event_service_test.go
  • Imported sync/atomic package.
  • Added an atomic.Uint64 field unregisterCount to mockEventStore to track unregistration calls.
  • Modified UnregisterDispatcher in mockEventStore to delete the dispatcher from dispatcherMap and increment unregisterCount.
• pkg/upstream/upstream.go
  • Extracted the retry condition logic for CreateTiStore into a new helper function isCreateTiStoreRetryable.
  • Updated isCreateTiStoreRetryable to distinguish between caller's context cancellation and internal client cancellation for retry decisions.
• pkg/upstream/upstream_test.go
  • Added TestIsCreateTiStoreRetryable to test the new retry logic, verifying correct behavior for both background and canceled contexts.

Activity

• The pull request description is a template, and no specific human activity (comments, reviews, or progress updates) has been recorded.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a4fe6f8a-c366-4717-a14b-f64b7abba2f9

📥 Commits

Reviewing files that changed from the base of the PR and between 0f8b6c5 and 38b66a3.

📒 Files selected for processing (1)

• logservice/eventstore/event_store.go

---

📝 Walkthrough

Walkthrough

Adds cleanup to event broker error paths to mark and unregister dispatchers on schema/register failures, extracts CreateTiStore retry decision into a helper, and ensures Pebble batch closure in the event store; corresponding tests added/updated.

Changes

Cohort / File(s)	Summary
Event Service: broker & tests pkg/eventservice/event_broker.go, pkg/eventservice/event_broker_test.go, pkg/eventservice/event_service_test.go	On addDispatcher error paths, mark dispatcher removed and call eventStore.UnregisterDispatcher(...) to prevent notifications; add test TestAddDispatcherUnregisterOnSchemaStoreError. Mock event store now tracks unregisterCount.
Upstream: retry logic & tests pkg/upstream/upstream.go, pkg/upstream/upstream_test.go	Extracts retryability check into isCreateTiStoreRetryable(ctx, err) and adds TestIsCreateTiStoreRetryable covering context-canceled behavior.
Event store: resource cleanup logservice/eventstore/event_store.go, go.mod	Add defer batch.Close() in writeEvents to ensure Pebble batch is closed; minor manifest update.

Sequence Diagram(s)

sequenceDiagram
    participant Broker as EventBroker
    participant Schema as SchemaStore
    participant Store as EventStore
    Broker->>Schema: register schema / table
    Schema--xBroker: return error
    Note right of Broker: mark dispatcher.isRemoved = true
    Broker->>Store: UnregisterDispatcher(changefeedID, dispatcherID)
    Store-->>Broker: acknowledge unregister
    Broker-->>Broker: cleanup local dispatcher state

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested reviewers

• wk989898
• flowbehappy

Poem

🐰 I hopped in code, a careful thrice—
When schema breaks, I cut the splice.
I mark the dispatcher, send it away,
Close the batch, and hop to play.
Tests cheer loud for a tidy day. 🎋

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 22.22% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: avoiding dispatcher registration failure during schema store initialization, which is the core problem addressed by the PR.
Description check	✅ Passed	The PR description includes a clear problem statement with error context, details about what is changed and how it works, highlights of the improvements, and references the related issue (#4272). However, the release note section is left incomplete with only the template placeholder.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

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• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch ldz/fix-event-broker0305

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[gemini-code-assist]

Code Review

This pull request introduces two main improvements. First, it enhances the error handling in addDispatcher by ensuring that if schemaStore.RegisterTable fails, the dispatcher is correctly unregistered from the event store and marked as removed to prevent race conditions. This is a solid fix for resource cleanup and stability. Second, it refactors the retry logic in CreateTiStore to be more robust against transient context.Canceled errors, which improves the reliability of upstream initialization. The changes are well-implemented and include corresponding tests to verify the new behavior.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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Details

Needs approval from an approver in each of these files:

• OWNERS [3AceShowHand,tenfyzhong]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-03-06 06:31:12.948585564 +0000 UTC m=+512517.526664758: ☑️ agreed by 3AceShowHand.
• 2026-03-06 06:51:28.848505851 +0000 UTC m=+513733.426585065: ☑️ agreed by tenfyzhong.

[lidezhu]

/retest