go/registry/metrics: Runtimes metrics: query for runtimes

[ptrus]

Runtime events are also triggered when a runtime is resumed, however we never subtract a runtime being suspended.

[kostko]

One downside here is that this will cause the query to be issued every 10 seconds.

Maybe combine the two approaches:

• Still subscribe to runtime events.
• But when an event happens, make a query to see how many runtimes there are instead of just incrementing.

Also, we should make sure that in case metrics are disabled, we don't use the metrics updater at all.

[ptrus]

One downside here is that this will cause the query to be issued every 10 seconds.

But we already do the same for Nodes & Entities, feels weird we'd only want to optimize the runtimes one (which will most likely also always be the smallest one).

[ptrus]

Anyway fixed.

[kostko]

Oh I didn't see that, sorry. So in this case I would be for keeping this consistent and the thing you proposer would actually be better, just maybe adjust the update interval (the current one seems excessive, something like 1 min should be enough). In case this becomes a problem we can optimize it later.

I would however disable the metrics updater in case metrics are disabled to avoid needless queries as currently it seems this is always running even if the metrics are not actually reported anywhere.

[kostko]

One minor nit, otherwise looks good.

[codecov]

Codecov Report

Merging #3161 into master will increase coverage by 0.02%.
The diff coverage is 20.00%.

@@            Coverage Diff             @@
##           master    #3161      +/-   ##
==========================================
+ Coverage   68.63%   68.66%   +0.02%     
==========================================
  Files         383      383              
  Lines       37463    37459       -4     
==========================================
+ Hits        25713    25721       +8     
+ Misses       8487     8477      -10     
+ Partials     3263     3261       -2     

Impacted Files	Coverage Δ
go/consensus/tendermint/full/full.go	61.97% <0.00%> (-0.59%)	⬇️
go/registry/metrics.go	0.00% <0.00%> (-88.64%)	⬇️
go/runtime/host/protocol/connection.go	62.16% <0.00%> (ø)
go/oasis-node/cmd/common/metrics/metrics.go	18.36% <100.00%> (+1.12%)	⬆️
go/worker/common/p2p/error/error.go	71.42% <0.00%> (-28.58%)	⬇️
...nsensus/tendermint/apps/staking/signing_rewards.go	21.62% <0.00%> (-5.41%)	⬇️
.../consensus/tendermint/apps/epochtime_mock/state.go	74.46% <0.00%> (-4.26%)	⬇️
go/storage/metrics.go	84.78% <0.00%> (-3.27%)	⬇️
go/storage/api/root_cache.go	72.41% <0.00%> (-2.30%)	⬇️
... and 30 more

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