Support for Metrics and Prometheus.

middlewares/metrics.go

@@ -0,0 +1,51 @@
+package middlewares
+
+import (
+	"github.com/go-kit/kit/metrics"
+	"net/http"
+	"strconv"
+	"time"
+)
+
+// Metrics is an Interface that must be satisfied by any system that
+// wants to expose and monitor metrics
+type Metrics interface {
+	getReqsCounter() metrics.Counter
+	getLatencyHistogram() metrics.Histogram
+	handler() http.Handler
+}
+
+// MetricsWrapper is a Negroni compatible Handler which relies on a
+// given Metrics implementation to expose and monitor Traefik metrics
+type MetricsWrapper struct {
+	Impl Metrics
+}
+
+// NewMetricsWrapper return a MetricsWrapper struct with
+// a given Metrics implementation e.g Prometheuss
+func NewMetricsWrapper(impl Metrics) *MetricsWrapper {
+	var metricsWrapper = MetricsWrapper{
+		Impl: impl,
+	}
+
+	return &metricsWrapper
+}
+
+func (m *MetricsWrapper) ServeHTTP(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+	start := time.Now()
+	prw := &responseRecorder{rw, http.StatusOK}
+	next(prw, r)
+	labels := []string{"code", strconv.Itoa(prw.StatusCode()), "method", r.Method}
+	m.Impl.getReqsCounter().With(labels...).Add(1)
+	m.Impl.getLatencyHistogram().With(labels...).Observe(float64(time.Since(start).Nanoseconds()) / 1000000)
+}
+
+func (rw *responseRecorder) StatusCode() int {
+	return rw.statusCode
+}
+
+// Handler is the chance for the Metrics implementation
+// to expose its metrics on a server endpoint
+func (m *MetricsWrapper) Handler() http.Handler {
+	return m.Impl.handler()
+}