vtorc: require topo for Healthy: true in /debug/health

[timvaillancourt]

Description

This PR addresses #17121 by requiring that we're able to reach the topology at least once (even if it's just empty) before returning Healthy: true in /debug/health. Today a VTOrc is considered healthy purely if it can write to it's own database

This is to prevent a vtorc deployment with a broken topo config to be seen as healthy, which in Kube can cause a bad config deploy to rollout to all nodes when it could fail on the first that it breaks

Also some error logging was consolidated so we don't log the topo failure multiple times for the same call (see below)

Example with this change:

tim@Tims-MacBook-Pro vitess % ./bin/vtorc --topo_global_server_address http://nowhere --topo_global_root /vitess --topo_implementation consul --config-name '' --port 15000
E1031 23:53:46.669158   54870 tablet_discovery.go:74] failed to initialize topo information: Get "http://nowhere/v1/kv/vitess/keyspaces/?keys=": dial tcp: lookup nowhere: no such host
E1031 23:54:01.675685   54870 vtorc.go:337] failed to refresh topo information: Get "http://nowhere/v1/kv/vitess/keyspaces/?keys=": dial tcp: lookup nowhere: no such host
E1031 23:54:16.677020   54870 vtorc.go:337] failed to refresh topo information: Get "http://nowhere/v1/kv/vitess/keyspaces/?keys=": dial tcp: lookup nowhere: no such host

And in another shell:

tim@Tims-MacBook-Pro vitess % curl -s localhost:15000/debug/health | jq .
{
  "Healthy": false,
  "LastReported": "2024-10-31T23:28:06.315105+01:00"
}

(previous to this PR "Healthy": true was returned)

Backport reason

I think this should be backported to prevent users from the scenario described above. This issue could lead to a user believing a VTOrc deployment is healthy when it's actually unable to load anything from the topo

Related Issue(s)

Resolves #17121

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]

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[codecov]

Codecov Report

Attention: Patch coverage is 2.38095% with 41 lines in your changes missing coverage. Please review.

Project coverage is 67.43%. Comparing base (551a5f7) to head (6ae638d).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/vtorc/logic/vtorc.go	0.00%	19 Missing ⚠️
go/vt/vtorc/logic/tablet_discovery.go	0.00%	15 Missing ⚠️
go/vt/vtorc/logic/keyspace_shard_discovery.go	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17129      +/-   ##
==========================================
+ Coverage   67.41%   67.43%   +0.01%     
==========================================
  Files        1574     1574              
  Lines      253294   253299       +5     
==========================================
+ Hits       170760   170806      +46     
+ Misses      82534    82493      -41     

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[timvaillancourt]

Added backport labels because I think it's unsafe for VTOrc to report it is healthy when it cannot see the topo. This could lead to outages if a vtorc config is invalid and deployed for some time

[shlomi-noach]

The change makes sense to me. I do have one question inline.

Re: backports, deferring to @deepthi

[GuptaManan100]

The changes LGTM. I'll defer to Deepthi as well as far as backports are concerned.

[deepthi]

Nice work, lgtm.
My understanding is that tests have been moved around but we haven't lost any coverage.

[deepthi]

The change makes sense to me. I do have one question inline.

Re: backports, deferring to @deepthi

Should be fine.