Add ChangeTabletTags RPC to vtctl, ChangeTags RPC to vttablet

[timvaillancourt]

Description

As discussed in #16377, this PR implements a new vtctld and corresponding vttablet RPC to allow the tags of a tablet to be changed

• VTCtld RPC: ChangeTabletTags
• VTTablet RPC: ChangeTags

The new RPC supports both replacing and merging the existing tags. This merging happens on the tablet under a lock

CLI

tim@Tims-MacBook-Pro vitess % ./bin/vtctldclient ChangeTabletTags --help 2>&1 | head       
Changes the tablet tags for the specified tablet, if possible.

Tags must be specified as key=value pairs.

Usage:
  vtctldclient ChangeTabletTags <alias> <tablet-tag> [ <tablet-tag> ... ]

Flags:
  -h, --help      help for ChangeTabletTags
  -r, --replace   Replace all tablet tags with the tags provided. By default tags are merged/updated.

Related Issue(s)

Resolves: #16873

Original discussion: #16377

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

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

Attention: Patch coverage is 40.82840% with 100 lines in your changes missing coverage. Please review.

Project coverage is 69.41%. Comparing base (056afc9) to head (c77ab79).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
go/cmd/vtctldclient/command/tablets.go	9.52%	19 Missing ⚠️
go/vt/vttablet/tabletmanager/rpc_actions.go	0.00%	15 Missing ⚠️
go/vt/vttablet/tmrpctest/test_tm_rpc.go	0.00%	12 Missing ⚠️
go/vt/vtcombo/tablet_map.go	0.00%	10 Missing ⚠️
go/vt/vttablet/grpctmclient/client.go	0.00%	9 Missing ⚠️
go/vt/vttablet/tabletmanager/tm_state.go	0.00%	8 Missing ⚠️
...t/vtctl/grpcvtctldserver/testutil/test_tmclient.go	61.11%	7 Missing ⚠️
go/vt/vttablet/grpctmserver/server.go	0.00%	7 Missing ⚠️
go/vt/topotools/tablet.go	84.61%	4 Missing ⚠️
go/vt/vtctl/grpcvtctldclient/client_gen.go	0.00%	4 Missing ⚠️
... and 3 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16857      +/-   ##
==========================================
- Coverage   69.45%   69.41%   -0.05%     
==========================================
  Files        1570     1570              
  Lines      203631   203798     +167     
==========================================
+ Hits       141441   141474      +33     
- Misses      62190    62324     +134     

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[timvaillancourt]

I assume this change would need some website docs that I'm happy to add. Any suggestions "where" this should go is appreciated!

[timvaillancourt]

👋 I've tested this on our infrastructure and things are looking good so far (after fixing one issue):

tvaillancourt@REDACTED:~$ vtctldclient $FLAGS GetTablet us_east_1b-0170348168 | jq .tags
{
  "hello": "world"
}
tvaillancourt@REDACTED:~$ vtctldclient $FLAGS ChangeTabletTags us_east_1b-0170348168 test=123
- [hello: "world"]
+ [hello: "world" test: "123"]
tvaillancourt@REDACTED:~$ vtctldclient $FLAGS GetTablet us_east_1b-0170348168 | jq .tags
{
  "hello": "world",
  "test": "123"
}

And --replace mode:

tvaillancourt@REDACTED:~$ vtctldclient $FLAGS ChangeTabletTags --replace us_east_1b-0170348168 replace=true 
- [hello: "world" test: "123"]
+ [replace: "true"]
tvaillancourt@REDACTED:~$ vtctldclient $FLAGS GetTablet us_east_1b-0170348168 | jq .tags
{
  "replace": "true"
}

And the stats:

tvaillancourt@REDACTED:~$ curl -s localhost:15000/metrics | grep tablet_tags
# HELP vttablet_tablet_tags Tablet tags key/values
# TYPE vttablet_tablet_tags gauge
vttablet_tablet_tags{key="replace",value="true"} 1

And the vttablet log:

I1002 06:06:49.280457 1915886 tm_state.go:243] Changing Tablet Tags: map[replace:true] for cell:"us_east_1b" uid:170348168

[GuptaManan100]

Rest LGTM!

[GuptaManan100]

I don't see this function being used anywhere other than test code. Is this right?

[timvaillancourt]

@GuptaManan100 correct, which is a bit confusing - but I copied ChangeType quite literally

[rohit-nayak-ps]

We generally keep the summary short and expect users to look at the vitess.io docs for the details.

[timvaillancourt]

@rohit-nayak-ps makes sense, updated!