release-23.1: kvcoord: Fix metrics tracking in mux rangefeed

[miretskiy]

Backport 1/1 commits from #107384.

/cc @cockroachdb/release

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Fix an observability bug in mux rangefeed which would incorrectly count various rangefeed related metrics (total ranges, catchup ranges, etc).

Fixes #106152
Fixes #106252

Release note: None
Release justification: fix observability/metrics accounting in mux rangefeed (disabled by default)

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues or test-only changes.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[miretskiy]

@erikgrinaker some conflicts occurred; but overall mostly clean backport.

[erikgrinaker]

I have a cluster running master which doesn't appear to be populating distsender.rangefeed.catchup_ranges. Going to confirm before approving this.

[miretskiy]

I have a cluster running master which doesn't appear to be populating distsender.rangefeed.catchup_ranges. Going to confirm before approving this.

I fixed an issue by adding metric struct tag to the new struct. Found it because chart.catalig test failed. I'm surprised it is still not fixed.

[erikgrinaker]

Yeah, that fix isn't merged yet. Can confirm that metrics are broken on master, so let's hold off on this.

[miretskiy]

Yeah, that fix isn't merged yet. Can confirm that metrics are broken on master, so let's hold off on this.

Can you pick my other metrics or to see if that's what was needed?

[erikgrinaker]

Works with #108062.

[miretskiy]

@erikgrinaker okay to merge this one then?

[erikgrinaker]

We should pull in the fix.

[miretskiy]

It's here already. That's how I discovered this issue (because of catalog_chart tests -- and those tests were removed on the master. note to self: we really need to have a linter or some such to protect against that)

[erikgrinaker]

Ah, missed that.