poolstats: support pgxpool metrics from two pools

[frostmar]

Fixes #1326

Support publishing pxgpool stats from two different pools as Prometheus metrics with different application_name labels.

A clair running in combo mode after:

$ curl -s localhost:6061/metrics | grep pgxpool

# HELP pgxpool_acquire_count Cumulative count of successful acquires from the pool.
# TYPE pgxpool_acquire_count counter
pgxpool_acquire_count{application_name="libindex"} 22
pgxpool_acquire_count{application_name="libvuln"} 2
# HELP pgxpool_acquire_duration_seconds_total Total duration of all successful acquires from the pool in nanoseconds.
# TYPE pgxpool_acquire_duration_seconds_total counter
pgxpool_acquire_duration_seconds_total{application_name="libindex"} 0.044675038
pgxpool_acquire_duration_seconds_total{application_name="libvuln"} 0.0325225
# HELP pgxpool_acquired_conns Number of currently acquired connections in the pool.
# TYPE pgxpool_acquired_conns gauge
pgxpool_acquired_conns{application_name="libindex"} 1
pgxpool_acquired_conns{application_name="libvuln"} 1
# HELP pgxpool_canceled_acquire_count Cumulative count of acquires from the pool that were canceled by a context.
# TYPE pgxpool_canceled_acquire_count counter
pgxpool_canceled_acquire_count{application_name="libindex"} 0
pgxpool_canceled_acquire_count{application_name="libvuln"} 0
# HELP pgxpool_constructing_conns Number of conns with construction in progress in the pool.
# TYPE pgxpool_constructing_conns gauge
pgxpool_constructing_conns{application_name="libindex"} 0
pgxpool_constructing_conns{application_name="libvuln"} 0
# HELP pgxpool_empty_acquire Cumulative count of successful acquires from the pool that waited for a resource to be released or constructed because the pool was empty.
# TYPE pgxpool_empty_acquire counter
pgxpool_empty_acquire{application_name="libindex"} 2
pgxpool_empty_acquire{application_name="libvuln"} 1
# HELP pgxpool_idle_conns Number of currently idle conns in the pool.
# TYPE pgxpool_idle_conns gauge
pgxpool_idle_conns{application_name="libindex"} 1
pgxpool_idle_conns{application_name="libvuln"} 0
# HELP pgxpool_max_conns Maximum size of the pool.
# TYPE pgxpool_max_conns gauge
pgxpool_max_conns{application_name="libindex"} 10
pgxpool_max_conns{application_name="libvuln"} 10
# HELP pgxpool_total_conns Total number of resources currently in the pool. The value is the sum of ConstructingConns, AcquiredConns, and IdleConns.
# TYPE pgxpool_total_conns gauge
pgxpool_total_conns{application_name="libindex"} 2
pgxpool_total_conns{application_name="libvuln"} 1

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.24%. Comparing base (473f247) to head (4c5aa9e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1328      +/-   ##
==========================================
- Coverage   56.29%   56.24%   -0.06%     
==========================================
  Files         266      266              
  Lines       16846    16838       -8     
==========================================
- Hits         9484     9471      -13     
- Misses       6398     6402       +4     
- Partials      964      965       +1     

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[frostmar]

bump - any chance of this being mergeable?

[crozzy]

Good find, I guess combo mode is getting slightly neglected these days

[crozzy]

Curious, do you run Clair in combo mode in production @frostmar?

[crozzy]

/fast-forward

[frostmar]

Curious, do you run Clair in combo mode ...

No, but we have a liveness probe added for the Postgres DB, which was recently updated to use a separate connpool, and I found it wasn't possible to see stats from more than one connpool! The combo mode made a nice recreate without needing anything outside the clair codebase