[release-23.0] VTGate: fix warming reads timeout context (#19674)

[vitess-bot]

Description

This is a backport of #19674

[vitess-bot]

Hello @timvaillancourt, there are conflicts in this backport.

Please address them in order to merge this Pull Request. You can execute the snippet below to reset your branch and resolve the conflict manually.

Make sure you replace origin by the name of the vitessio/vitess remote

git fetch --all
gh pr checkout 19728
git reset --hard origin/release-23.0
git cherry-pick -m 1 8c937df416bc9e3f30b5a06953e05f6fd9367a01

[timvaillancourt]

Resolved conflicts for backport of #19674 to release-23.0.

Conflicting files:

• go/vt/vtgate/executorcontext/vcursor_impl.go — Removed old timeout logic from CloneForReplicaWarming, kept new WarmingReadsContext method.
• go/vt/vtgate/engine/route.go — Moved CloneForReplicaWarming inside channel select, used warmingCtx. Kept queries instead of warmingQueries since removeForUpdateLocks doesn't exist on this branch.
• go/vt/vtgate/engine/route_warming_reads_test.go — Removed QueryStatement references (not on this branch), updated FOR UPDATE test expectations to keep the clause.

Reverted: go/vt/wrangler/fake_dbclient_test.go (not in upstream PR, dragged in by cherry-pick).

[Copilot]

Pull request overview

Backport of #19674 to release-23.0 to ensure VTGate “warming reads” use a dedicated, correctly-scoped timeout context that starts when the warming goroutine runs and is not canceled when the primary request finishes.

Changes:

• Introduces VCursor.WarmingReadsContext(ctx) to create a timeout-bounded, parent-detached context (and cancel func) for warming reads.
• Updates warming read execution to use the warming context for routing and execution, and to avoid unnecessary cloning when the warming channel is full.
• Adds targeted tests covering timeout behavior, parent-cancel independence, and channel-full dropping.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
go/vt/vtgate/executorcontext/vcursor_impl.go	Moves warming timeout/context creation into WarmingReadsContext, fixes cancel handling, and updates replica-warming clone setup.
go/vt/vtgate/engine/route.go	Uses WarmingReadsContext inside the warming goroutine and clones only after acquiring a channel slot.
go/vt/vtgate/engine/primitive.go	Extends VCursor interface with WarmingReadsContext and documents intended usage.
go/vt/vtgate/engine/fake_vcursor_test.go	Updates test vcursor helpers to satisfy the extended VCursor interface and adds a ResolveDestinations hook.
go/vt/vtgate/engine/route_warming_reads_test.go	Adds new tests validating warming context behavior (deadline, independence from parent cancel, dropping on full channel, deadline exceeded).

[Copilot]

Test name TestWarmingReadsSkipsForUpdate doesn’t match what the test actually validates (context deadline independence / propagation and execution across multiple query shapes, including a regular SELECT). Renaming this test to reflect its assertions would make failures easier to interpret.

Suggested change

	func TestWarmingReadsSkipsForUpdate(t *testing.T) {
	func TestWarmingReadsContextDeadlineAndQueryShapes(t *testing.T) {

[codecov]

Codecov Report

❌ Patch coverage is 35.71429% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.70%. Comparing base (550459d) to head (c67bb6f).
⚠️ Report is 11 commits behind head on release-23.0.

Files with missing lines	Patch %	Lines
go/vt/vtgate/executorcontext/vcursor_impl.go	0.00%	9 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (550459d) and HEAD (c67bb6f). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (550459d)	HEAD (c67bb6f)
	1	0

Additional details and impacted files

@@                Coverage Diff                @@
##           release-23.0   #19728       +/-   ##
=================================================
- Coverage         69.45%   45.70%   -23.76%     
=================================================
  Files              1607       67     -1540     
  Lines            215090     7181   -207909     
=================================================
- Hits             149397     3282   -146115     
+ Misses            65693     3899    -61794     

Flag	Coverage Δ
partial	45.70% <35.71%> (?)

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