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]

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 2.43902% with 40 lines in your changes missing coverage. Please review.

Project coverage is 67.41%. Comparing base (f6067e0) to head (621e2a6).

Files with missing lines	Patch %	Lines
go/vt/vtorc/logic/vtorc.go	0.00%	20 Missing ⚠️
go/vt/vtorc/logic/tablet_discovery.go	0.00%	13 Missing ⚠️
go/vt/vtorc/logic/keyspace_shard_discovery.go	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17129      +/-   ##
==========================================
+ Coverage   67.40%   67.41%   +0.01%     
==========================================
  Files        1570     1570              
  Lines      252903   252907       +4     
==========================================
+ Hits       170460   170494      +34     
+ Misses      82443    82413      -30     

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

[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

[shlomi-noach]

Can you please explain how do you mean "We can wait forever (context.Background()) for this call."?

[timvaillancourt]

@shlomi-noach this comment is confusing, yeah

What I intended with adding the context.Context is to prevent ticks from overlapping here (currently no timeout)

This area of the code is ran once before the ticker starts at vtorc init time, so I figured waiting forever had no risk. Adding a timeout here as well wouldn't hurt either I suppose

[timvaillancourt]

is to prevent ticks from overlapping here

Sorry, not "overlapping" per se, but one loop iteration stalling things