Implementing Metrics and Monitoring

import (
    "github.com/prometheus/client_golang/prometheus"
    "github.com/prometheus/client_golang/prometheus/promhttp"
)
http.Handle("/metrics", promhttp.Handler())
go http.ListenAndServe(":9090", nil)

reqs := prometheus.NewCounterVec(
    prometheus.CounterOpts{Name: "grpc_requests_total"},
    []string{"method", "code"},
)
prometheus.MustRegister(reqs)
reqs.WithLabelValues(method, code).Inc()

lat := prometheus.NewHistogramVec(
    prometheus.HistogramOpts{
        Name: "grpc_request_duration_seconds",
        Buckets: []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2, 5},
    },
    []string{"method"},
)
lat.WithLabelValues(method).Observe(dur.Seconds())

func Metrics(reqs *prometheus.CounterVec, lat *prometheus.HistogramVec) grpc.UnaryServerInterceptor {
    return func(ctx context.Context, req any, info *grpc.UnaryServerInfo,
        h grpc.UnaryHandler) (any, error) {
        start := time.Now()
        res, err := h(ctx, req)
        code := status.Code(err).String()
        reqs.WithLabelValues(info.FullMethod, code).Inc()
        lat.WithLabelValues(info.FullMethod).Observe(time.Since(start).Seconds())
        return res, err
    }
}

sum(rate(grpc_requests_total{code!="OK"}[5m])) by (method)
/
sum(rate(grpc_requests_total[5m])) by (method)