Respect tolerable replication lag even when the new primary has been provided in PRS

[GuptaManan100]

Description

This PR fixes the bug described in #15089.
Now when running PRS, if both the new primary and the tolerable replication lag has been provided, we will check that the new primary tablet actually has a replication lag lower than what we can tolerate, otherwise we'll fail the PRS quickly.

Related Issue(s)

• Fixes Bug Report: TolerableReplicationLag not checked if the new primary is provided in PRS #15089

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 was added or is not required

Deployment Notes

[vitess-bot]

Review Checklist

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• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

Attention: 383 lines in your changes are missing coverage. Please review.

Comparison is base (eddb39e) 47.29% compared to head (87d04bd) 40.88%.
Report is 98 commits behind head on main.

Files	Patch %	Lines
go/vt/proto/vtctldata/vtctldata_vtproto.pb.go	0.00%	157 Missing ⚠️
go/vt/vtgate/evalengine/cached_size.go	21.21%	25 Missing and 1 partial ⚠️
go/vt/mysqlctl/backupengine.go	9.09%	20 Missing ⚠️
go/vt/vtctl/workflow/traffic_switcher.go	0.00%	20 Missing ⚠️
go/vt/mysqlctl/builtinbackupengine.go	5.88%	16 Missing ⚠️
.../vtgate/planbuilder/operators/delete_with_input.go	48.27%	14 Missing and 1 partial ⚠️
go/vt/vtgate/evalengine/expr_tuple_bvar.go	64.10%	10 Missing and 4 partials ⚠️
go/vt/vtctl/workflow/server.go	84.31%	6 Missing and 2 partials ⚠️
go/vt/vtgate/engine/delete_with_input.go	83.33%	5 Missing and 3 partials ⚠️
go/vt/vtgate/evalengine/fn_time.go	91.13%	3 Missing and 4 partials ⚠️
... and 35 more

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #15090       +/-   ##
===========================================
- Coverage   47.29%   40.88%    -6.42%     
===========================================
  Files        1137     1453      +316     
  Lines      238684   368141   +129457     
===========================================
+ Hits       112895   150516    +37621     
- Misses     117168   201438    +84270     
- Partials     8621    16187     +7566     

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[maxenglander]

Instead of the current approach, what if you:

• Copied tabletMap (line 162), filtering out all tablets except for the one specified in opts.NewPrimaryAlias,
• Removed the conditional check on line 173 for opts.NewPrimaryAlias,

I think that would reduce code complexity and reduce logic drift in the future when new behaviors are added to the ChooseNewPrimary path.

[deepthi]

why does CodeCov say this?

Report is 81 commits behind head on main.

[GuptaManan100]

I think that would reduce code complexity and reduce logic drift in the future when new behaviors are added to the ChooseNewPrimary path.

@deepthi @maxenglander I have made the required changes. I have chosen the approach that Deepthi pointed out, that ends up being a cleaner solution. I had to make a couple more changes to preserve the behaviour wherein we don't call findPositionAndLagForTablet when new primary has been provided but no tolerable replication lag is given.

I think the code looks good now, could you two please review it again?

Report is 81 commits behind head on main.

I have no idea why codecov says this.

[maxenglander]

LGTM! Some minor comments.

[deepthi]

Looks good.

[deepthi]

💯