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

  • Revised commit wait timeout handling to strictly enforce configured timeout values, immediately returning an error when timeout is not set.

• Tests

  • Added test coverage for no-wait transaction commit scenarios.

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📝 Walkthrough

Walkthrough

The changes modify timeout handling in the commit-wait-until-TSO flow. When the timeout is zero, GetTimestampForCommit now immediately returns an error instead of using a default wait duration. A corresponding integration test validates this zero-timeout behavior.

Changes

Cohort / File(s)	Summary
Commit Wait Timeout Logic txnkv/transaction/txn.go	Replaced default 1-second maxSleep with direct use of commitWaitUntilTSOTimeout. When timeout is zero, immediately returns ErrCommitTSLag error instead of attempting wait.
Test Options and Scenarios integration_tests/option_test.go	Added setNoWait test flag to options struct. Introduced "no wait" test case that forces SetCommitWaitUntilTSOTimeout to 0 and validates error handling.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• txnkv: fix SetCommitWaitUntilTSOTimeout does not work in causal consistency #1847: Modifies the commit-wait-until-TSO invocation conditions (adding checks when commitWaitUntilTSO > 0), complementing this PR's timeout handling changes.

Suggested labels

lgtm, approved, size/M

Suggested reviewers

• tiancaiamao
• cfzjywxk
• ekexium

Poem

🐰 A timeout of zero means wait not at all,
No slumber, no linger, just answer the call!
The test catches errors with precision so tight,
Active-active awaits—this logic's just right! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main changes: adding support for SetCommitWaitUntilTSOTimeout and implementing no-wait behavior when timeout is set to zero.
Linked Issues check	✅ Passed	The PR implements explicit no-wait mode for commit-wait TSO checks via SetCommitWaitUntilTSOTimeout(0), enabling fast-fail behavior for active-active replication scenarios as required by issue #1854.
Out of Scope Changes check	✅ Passed	All changes are directly related to implementing SetCommitWaitUntilTSOTimeout support and no-wait behavior. The test additions and transaction logic modifications align with the stated objectives.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

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• Post copyable unit tests in a comment

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[lcwangchao]

/retest

[lcwangchao]

@coderabbitai review this PR again

[coderabbitai]

@lcwangchao, I'll review the changes in this PR again.

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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)

320-324: ⚠️ Potential issue | 🟡 Minor

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

The comment on GetCommitWaitUntilTSOTimeout says zero means "not set and the default timeout should be used," but with this PR, zero now means immediate failure. This will confuse future readers.

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
+// GetCommitWaitUntilTSOTimeout returns the timeout to wait for the commit TSO to reach the expected value.
+// If it returns zero, the commit will fail immediately with ErrCommitTSLag when PD TSO lags.

🧹 Nitpick comments (1)

txnkv/transaction/txn.go (1)

1886-1917: Duplicate comment block and clean logic for the zero-timeout path look correct.

Two issues in this segment:

1. The comment block at lines 1886–1888 is duplicated verbatim at lines 1907–1909. The first occurrence (1886–1888) is now orphaned — it no longer sits adjacent to the maxSleep assignment. Please remove one of the two.

2. The zero-timeout fast-fail logic (lines 1910–1917) is correct and aligns with the PR objective.

Remove the duplicate comment block

-	// maxSleep is the maximum time we are allowed to wait for the expected commit TS.
-	// It is 1 second by default to avoid infinite blocking but can be overridden by commitWaitUntilTSOTimeout.
-	// If the TSO drift is larger than the maxSleep, return error directly.
 	start := time.Now()

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

The full list of commands accepted by this bot can be found here.

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Details

Needs approval from an approver in each of these files:

• OWNERS [cfzjywxk,ekexium]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-02-09 03:23:47.001017572 +0000 UTC m=+155242.695157422: ☑️ agreed by cfzjywxk.
• 2026-02-09 03:27:59.424904287 +0000 UTC m=+155495.119044137: ☑️ agreed by ekexium.

[lcwangchao]

/retest