Query serving: incorporate mirror query results in log stats, fix mirror query max lag bug

[maxenglander]

Description

This PR adds a few new fields to log stats to provide visibility into traffic mirroring. The idea behind traffic mirroring is to see if the target of a VReplication workflow will perform as well as the source when queries are sent to it. In order to make that determination, we can send mirrored queries to the target with MirrorTraffic. However, we also need a way to compare the query execution times and errors of the source vs. target queries.

While working on this PR, I noticed a bug with how mirror target queries are bounded. The VTGate mirror primitive was written with the intention of having the mirror target be canceled if it continues executing for too long (hardcoded at 100ms) after the source primitive finishes executing. However as it is currently written the mirror target will be canceled if it executes for more than 100ms. This PR fixes that.

Related Issue(s)

Fix #16877
Close #16878
Close #13772

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation: content/end/docs/21.0: mirror queries can be seen in VTGate /debug/querylog website#1858

Deployment Notes

None

[vitess-bot]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

• Ensure that the Pull Request has a descriptive title.
• Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

Tests

• Bug fixes should have at least one unit or end-to-end test, enhancement and new features should have a sufficient number of tests.

Documentation

• Apply the release notes (needs details) label if users need to know about this change.
• New features should be documented.
• There should be some code comments as to why things are implemented the way they are.
• There should be a comment at the top of each new or modified test to explain what the test does.

New flags

• Is this flag really necessary?
• Flag names must be clear and intuitive, use dashes (-), and have a clear help text.

If a workflow is added or modified:

• Each item in Jobs should be named in order to mark it as required.
• If the workflow needs to be marked as required, the maintainer team must be notified.

Backward compatibility

• Protobuf changes should be wire-compatible.
• Changes to _vt tables and RPCs need to be backward compatible.
• RPC changes should be compatible with vitess-operator
• If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.43%. Comparing base (978c59d) to head (aff7830).
Report is 14 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #16879   +/-   ##
=======================================
  Coverage   69.43%   69.43%           
=======================================
  Files        1571     1571           
  Lines      203195   203237   +42     
=======================================
+ Hits       141079   141119   +40     
- Misses      62116    62118    +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[GuptaManan100]

LGTM!