refactor: implement connection tracking in metrics#4672
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mkleczek wants to merge 1 commit intoPostgREST:mainfrom
Open
refactor: implement connection tracking in metrics#4672mkleczek wants to merge 1 commit intoPostgREST:mainfrom
mkleczek wants to merge 1 commit intoPostgREST:mainfrom
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This was referenced Feb 25, 2026
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Fix should have an entry on the CHANGELOG |
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| SQL.ReadyForUseConnectionStatus -> atomically $ | ||
| SH.insert identity uuid connTrackConnected *> | ||
| SH.focus Focus.delete identity uuid connTrackInUse | ||
| SQL.TerminatedConnectionStatus _ -> atomically $ | ||
| SH.focus Focus.delete identity uuid connTrackConnected *> | ||
| SH.focus Focus.delete identity uuid connTrackInUse | ||
| SQL.InUseConnectionStatus -> atomically $ | ||
| SH.insert identity uuid connTrackInUse | ||
| _ -> mempty |
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Could there be noticeable overhead now that we have the insert/focus logic?
Doesn't look like it from the mixed loadtest but want to make sure.
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| connectionCounts :: ConnTrack -> IO ConnStats | ||
| connectionCounts = atomically . fmap (uncurry ConnStats) . bisequenceA . both SH.size . (connTrackConnected &&& connTrackInUse) |
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This is purely used for testing right? If so, a comment here would be good for clarity.
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This is purely used for testing right? If so, a comment here would be good for clarity.
@steve-chavez It is not. The actual Metric is implementation is based on ConnTrack:
https://github.com/mkleczek/postgrest/blob/7e9df6416195b3d9c534c1f1c4aeb39865869f45/src/PostgREST/Metrics.hs#L59
Also - this function is crucial for #4643 - see: https://github.com/mkleczek/postgrest/blob/f3e06920544b88d26809e75d2652d2ed6a4ef8f3/src/PostgREST/AppState.hs#L421
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DISCLAIMER: This commit was authored entirely by a human without the assistance of LLMs. Right now metrics observation handler does not track database connections but updates a single Gauge based on HasqlPoolObs events. This is problematic because Hasql pool reports various connection events in multiple phases. The connection state machine is not simple and to precisely report the number of connections in various states, it is necessary to track their lifecycles. This change adds a ConnTrack data structure and logic to track database connections lifecycles. At the moment it supports "connected" and "inUse" connection counts precisely. The "pgrst_db_pool_available" metric is implemented on top of ConnTrack instead of a simple Gauge.
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DISCLAIMER:
This commit was authored entirely by a human without the assistance of LLMs.Right now metrics observation handler does not track database connections but updates a single Gauge based on HasqlPoolObs events.
This is problematic because Hasql pool reports various connection events in various states that make it impossible to predict the state change from the received event. The connection state machine is not simple and to precisely report the number of connections in various states, it is necessary to track their lifecycles.
Fixes #4622