schemastore: clean up tombstone keyspace store

[asddongmen]

What problem does this PR solve?

Issue Number: close #6156

After PD tombstones a keyspace, each TiCDC node that registered it keeps the per-keyspace schema store alive. Its GC keeper retries the rejected safepoint update every two minutes, while the DDL subscription and other periodic schema-store tasks also remain active until process shutdown.

What is changed and how it works?

After a NextGen safepoint refresh fails, the keeper loads authoritative keyspace metadata from PD. If PD confirms the irreversible TOMBSTONE state, the schema store:

• removes the exact store instance from keyspaceSchemaStoreMap and records the terminal keyspace ID to prevent lazy re-registration;
• cancels the per-keyspace context and unblocks resolved-ts waiters;
• drains active schema-store API calls and the resolved-ts apply goroutine;
• unsubscribes the keyspace DDL spans and closes persistent storage.

The terminal lifecycle event is logged once. Successful refreshes add no PD request. Enabled keyspaces, temporary refresh failures, and metadata lookup failures keep the existing retry behavior.

Check List

Tests

• Unit test
  • NextGen and classic schema-store lifecycle/GC-keeper tests
  • NextGen TOMBSTONE lifecycle tests with the race detector

Questions

Will it cause performance regression or break compatibility?

No. The additional PD metadata request and teardown occur only after a failed NextGen safepoint refresh. Healthy refreshes and classic behavior are unchanged.

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

No. This fixes an internal lifecycle error path without changing user-facing APIs or configuration.

Release note

Fix TiCDC retaining schema-store tasks and repeatedly refreshing the GC safepoint after a keyspace becomes tombstone.

Summary by CodeRabbit

• Bug Fixes
  • Schema stores now stop refreshing safepoints when a keyspace is tombstoned.
  • Tombstoned keyspaces are no longer recreated after shutdown.
  • Schema-store operations now terminate promptly when their context is canceled.
  • Shutdown waits for active operations and background processing before releasing storage.
  • DDL subscriptions are cleaned up when a schema store closes.
  • Temporary refresh failures continue to be handled without unnecessarily stopping processing.

[coderabbitai]

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Run ID: 12254912-c087-4f94-b17a-2106009dbc10

📥 Commits

Reviewing files that changed from the base of the PR and between 40dbd02 and 6a1cb55.

📒 Files selected for processing (4)

• logservice/schemastore/ddl_job_fetcher.go
• logservice/schemastore/gc_keeper.go
• logservice/schemastore/schema_store.go
• logservice/schemastore/schema_store_test.go

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📝 Walkthrough

Walkthrough

The schema store now stops GC refreshes for tombstoned keyspaces and removes their stores through synchronized cleanup. API access, background workers, DDL subscriptions, and persistent storage follow the store lifecycle.

Changes

Tombstoned keyspace lifecycle

Layer / File(s)	Summary
Tombstone-aware GC refresh logservice/schemastore/gc_keeper.go, logservice/schemastore/gc_keeper_test.go	The keeper checks PD state after refresh failures and stops for non-classic TOMBSTONE keyspaces. Tests cover successful refreshes, tombstones, temporary errors, and lookup failures.
Synchronized schema store shutdown logservice/schemastore/schema_store.go, logservice/schemastore/ddl_job_fetcher.go	The store tracks active calls and workers, cancels operations, unsubscribes DDL jobs, waits for completion, and closes persistent storage.
Tombstone registry and API guards logservice/schemastore/schema_store.go	The store records removed keyspaces as tombstones, rejects later registration, and uses lifecycle locks during API access and cleanup.
Cleanup validation logservice/schemastore/schema_store_test.go	Tests verify that cleanup waits for active users and closes subscriptions, context, and Pebble storage.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Severity of issue fixed: Medium

Suggested reviewers: lidezhu, 3aceshowhand, tenfyzhong

Merge Risk: ⚪ Minimal · up to ff3ae

The change cleans up tombstoned keyspace schema stores while preserving retry behavior, with lifecycle cleanup covered by tests. No merge-blocking risk is currently established.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 16.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the primary change: cleaning up the schema store for a tombstoned keyspace.
Description check	✅ Passed	The description includes the required issue reference, problem statement, implementation details, tests, compatibility assessment, documentation assessment, and release note.
Linked Issues check	✅ Passed	The changes address issue #6156 by stopping GC safepoint retries after PD confirms TOMBSTONE, removing and tombstoning the store, canceling its lifecycle, unsubscribing DDL spans, closing storage, and…
Out of Scope Changes check	✅ Passed	The modified implementation and tests are directly related to tombstoned keyspace cleanup, GC keeper shutdown, schema-store lifecycle management, and verification of those behaviors. No unrelated chan…

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-09-03 07:34:16.289044937 +0000 UTC m=+1351091.460139050: ☑️ agreed by lidezhu.
• 2026-09-04 09:10:42.266935705 +0000 UTC m=+1443277.438029820: ☑️ agreed by 3AceShowHand.

[asddongmen]

/retest

[asddongmen]

/test all

[asddongmen]

/retest

[asddongmen]

/retest

[asddongmen]

/retest

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-nextgen-202603: #6231.
But this PR has conflicts, please resolve them!