Add prometheus requests processed and request latencies metric gathering wrapper

prometheus.go

@@ -0,0 +1,49 @@
+package prometheus
+
+import (
+	"context"
+	"github.com/micro/go-micro/server"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func NewHandlerWrapper() server.HandlerWrapper {
+	opsCounter := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "go_micro_requests_total",
+			Help: "How many go-miro requests processed, partitioned by method and status",
+		},
+		[]string{"method", "status"},
+	)
+
+	timeCounter := prometheus.NewSummaryVec(
+		prometheus.SummaryOpts{
+			Name: "go_micro_request_durations_microseconds",
+			Help: "Service method request latencies in microseconds",
+		},
+		[]string{"method"},
+	)
+
+	prometheus.MustRegister(opsCounter)
+	prometheus.MustRegister(timeCounter)
+
+	return func(fn server.HandlerFunc) server.HandlerFunc {
+		return func(ctx context.Context, req server.Request, rsp interface{}) error {
+			name := req.Endpoint()
+
+			timer := prometheus.NewTimer(prometheus.ObserverFunc(func(v float64) {
+				us := v * 1000000 // make microseconds
+				timeCounter.WithLabelValues(name).Observe(us)
+			}))
+			defer timer.ObserveDuration()
+
+			err := fn(ctx, req, rsp)
+			if err == nil {
+				opsCounter.WithLabelValues(name, "success").Inc()
+			} else {
+				opsCounter.WithLabelValues(name, "fail").Inc()
+			}
+
+			return err
+		}
+	}
+}