txnkv: support to SetCommitWaitUntilTSOTimeout and do not wait TSO

[lcwangchao]

Summary

close #1854

This PR adds explicit no-wait behavior for commit-wait TSO checks.

When SetCommitWaitUntilTSO(...) is enabled, users can now set
SetCommitWaitUntilTSOTimeout(0) to fail immediately if PD TSO is behind the expected commit-wait timestamp, instead of waiting.

Motivation

In active-active replication scenarios, some callers prefer a fast-fail path rather than waiting for TSO catch-up. A zero timeout should represent this intent clearly.

Behavior Change

• commitWaitUntilTSOTimeout > 0: keep existing bounded-wait behavior.
• commitWaitUntilTSOTimeout == 0: return ErrCommitTSLag immediately on the first lag check.
• Default behavior is unchanged because the transaction default timeout remains 1s.

Tests

Added integration coverage in TestSetCommitWaitUntilTSO for a new "no wait" case:

• enable commit-wait TSO;
• set timeout to 0;
• mock lagging TSO;
• verify the commit path returns error immediately.

Summary by CodeRabbit

• Bug Fixes

  • Improved timeout handling for commit operations. When a zero timeout is configured, the system now immediately returns an error instead of applying a default timeout, providing stricter control over commit wait behavior.

• Tests

  • Added test coverage for no-wait scenarios with commit operations.

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📝 Walkthrough

Walkthrough

This change modifies the CommitWaitUntilTSO timeout handling in both tests and the transaction implementation. When the timeout is set to zero, the system now immediately returns an error instead of falling back to a default behavior. The test infrastructure is updated to exercise this no-wait scenario.

Changes

Cohort / File(s)	Summary
CommitWaitUntilTSO timeout implementation txnkv/transaction/txn.go	Modified GetTimestampForCommit to treat zero timeout as an immediate error condition, replacing the previous default 1-second cap with the configured timeout value directly.
CommitWaitUntilTSO test coverage integration_tests/option_test.go	Added setNoWait test parameter to exercise zero timeout scenario, with test case expecting error for no-wait behavior.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

The changes touch a critical commit path with modified timeout semantics and new error handling, but are localized to two well-scoped files with relatively few lines modified.

Possibly related PRs

• txnkv: fix SetCommitWaitUntilTSOTimeout does not work in causal consistency #1847 — Changes the invocation conditions for GetTimestampForCommit when commitWaitUntilTSO > 0 under causal consistency, complementing the zero-timeout error handling logic introduced here.

Suggested labels

lgtm, approved, size/M

Suggested reviewers

• tiancaiamao
• cfzjywxk
• ekexium

Poem

🐰 A rabbit hops through timeout schemes,
Where zero waits break default dreams,
No more delay, no fallback sleep—
Errors fast, commitments deep! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically refers to the main changes: adding support for SetCommitWaitUntilTSOTimeout and implementing no-wait behavior for TSO, which directly matches the PR objectives and file modifications.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[lcwangchao]

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

txnkv/transaction/txn.go (1)

373-377: ⚠️ Potential issue | 🟡 Minor

Stale doc comment: zero now means "no wait", not "use default".

The comment on GetCommitWaitUntilTSOTimeout says zero means "it is not set and the default timeout should be used," but with this PR, zero now triggers an immediate ErrCommitTSLag. This should be updated to reflect the new semantics.

📝 Suggested fix

 // GetCommitWaitUntilTSOTimeout returns the timeout to wait for the commit tso reach the expected value.
-// If it returns zero, it means it is not set and the default timeout should be used
+// If it returns zero, the commit will fail immediately with ErrCommitTSLag when the PD TSO lags behind the expected value.
 func (txn *KVTxn) GetCommitWaitUntilTSOTimeout() time.Duration {
 	return txn.commitWaitUntilTSOTimeout
 }

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, ekexium

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Details

Needs approval from an approver in each of these files:

• OWNERS [cfzjywxk,ekexium]
• txnkv/OWNERS [cfzjywxk,ekexium]

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:

• 2026-02-09 03:23:58.371097078 +0000 UTC m=+155254.065236918: ☑️ agreed by cfzjywxk.
• 2026-02-09 03:28:09.769493558 +0000 UTC m=+155505.463633398: ☑️ agreed by ekexium.