pg-pool-monitor: Prometheus Metrics for Your PostgreSQL Connection Pool

PostgreSQL connection pool exhaustion is one of the most insidious production failures you can face. Your app looks healthy — process is up, CPU is calm, memory is fine — but requests are silently queueing behind a full connection pool. By the time you notice latency spiking, the waiting queue has already grown to hundreds of requests and your database is under maximum load. The fix isn't complicated. You need to see what your pool is doing before it becomes a problem. That's exactly what pg-pool-monitor was built for. The Problem with pg Pool Observability node-postgres (the pg package) is the default PostgreSQL driver for Node.js. It's battle-tested and does its job well. But pg.Pool gives you exactly three counters: pool . totalCount // All connections (active + idle) pool . idleCount // Connections sitting idle pool . waitingCount // Requests queued waiting for a free connection These three numbers contain everything you need to know about your pool's health — but they're just sitt