Why doesn't CRDB use prometheus's client_golang to implement metrics?

I find CRDB self implemented counter, gauge, histogram, and metricsRegistry. Why not use GitHub - prometheus/client_golang: Prometheus instrumentation library for Go applications?

Could somebody help me?

Cockroach does use prometheus/client_golang internally. It also adds some additional functionality above it and has its own internal metrics collection system. See cockroach/prometheus_exporter.go at master · cockroachdb/cockroach · GitHub.

Can you help me understand the motivation behind the question?

Hi @ajwerner, I am a CRDB learner, I 'm reading the source code of CRDB, and would like to contribute to it someday.

But seems CRDB implements its Counter, Gauge, Histogram. Why not use the ones that client_golang offers? And I haven’t seem CounterVec, HistogramVec in the source code…