Add WIP middlewares

Author: stuartnelson3

prometheus/promhttp/middleware.go

@@ -0,0 +1,117 @@
+// Copyright 2016 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Copyright (c) 2013, The Prometheus Authors
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be found
+// in the LICENSE file.
+
+package promhttp
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptrace"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// ClientTrace adds middleware providing a histogram of outgoing request
+// latencies, partitioned by http client, request host and httptrace event.
+func ClientTrace(httpClientName string) middlewareFunc {
+	hist := prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace:   "outgoing_httptrace",
+		Name:        "duration_seconds",
+		ConstLabels: prometheus.Labels{"client": httpClientName},
+		Help:        "Histogram of outgoing request latencies.",
+		Buckets:     []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10},
+	},
+		[]string{"host", "event"},
+	)
+
+	if err := prometheus.Register(hist); err != nil {
+		if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
+			hist = are.ExistingCollector.(*prometheus.HistogramVec)
+		} else {
+			panic(err)
+		}
+	}
+
+	return func(req *http.Request, next Middleware) (*http.Response, error) {
+		var (
+			host  = req.URL.Host
+			start = time.Now()
+		)
+
+		trace := &httptrace.ClientTrace{
+			DNSStart: func(_ httptrace.DNSStartInfo) {
+				hist.WithLabelValues(host, "DNSStart").Observe(time.Since(start).Seconds())
+			},
+			DNSDone: func(_ httptrace.DNSDoneInfo) {
+				hist.WithLabelValues(host, "DNSDone").Observe(time.Since(start).Seconds())
+			},
+			ConnectStart: func(_, _ string) {
+				hist.WithLabelValues(host, "ConnectStart").Observe(time.Since(start).Seconds())
+			},
+			ConnectDone: func(net, addr string, err error) {
+				if err != nil {
+					return
+				}
+				hist.WithLabelValues(host, "ConnectDone").Observe(time.Since(start).Seconds())
+			},
+			GotConn: func(_ httptrace.GotConnInfo) {
+				hist.WithLabelValues(host, "GotConn").Observe(time.Since(start).Seconds())
+			},
+			GotFirstResponseByte: func() {
+				hist.WithLabelValues(host, "GotFirstResponseByte").Observe(time.Since(start).Seconds())
+			},
+		}
+		req = req.WithContext(httptrace.WithClientTrace(context.Background(), trace))
+
+		return next(req)
+	}
+}
+
+// InFlight is middleware that instruments number of open requests partitioned
+// by http client and request host.
+var InFlight = func(httpClientName string) middlewareFunc {
+	gauge := prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace:   "outgoing",
+		Name:        "open_requests",
+		ConstLabels: prometheus.Labels{"client": httpClientName},
+		Help:        "Gauge of open outgoing requests.",
+	},
+		[]string{"host"},
+	)
+
+	if err := prometheus.Register(gauge); err != nil {
+		if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
+			gauge = are.ExistingCollector.(*prometheus.GaugeVec)
+		} else {
+			panic(err)
+		}
+	}
+
+	return func(req *http.Request, next Middleware) (*http.Response, error) {
+		host := req.URL.Host
+		gauge.WithLabelValues(host).Inc()
+
+		resp, err := next(req)
+
+		gauge.WithLabelValues(host).Dec()
+
+		return resp, err
+	}
+}

prometheus/promhttp/middleware_test.go

@@ -0,0 +1,76 @@
+// Copyright 2016 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Copyright (c) 2013, The Prometheus Authors
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be found
+// in the LICENSE file.
+
+package promhttp
+
+import (
+	"log"
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func TestClientTraceMiddleware(t *testing.T) {}
+
+func ExampleMiddleware() {
+	t := time.NewTicker(time.Second)
+	defer t.Stop()
+
+	client := *http.DefaultClient
+	client.Timeout = 500 * time.Millisecond
+
+	counter := prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "request_length_counter",
+		Help: "Counter of request length.",
+	})
+	prometheus.MustRegister(counter)
+	customMiddleware := func(req *http.Request, next Middleware) (*http.Response, error) {
+		counter.Add(float64(req.ContentLength))
+
+		return next(req)
+	}
+
+	promclient, err := NewClient(
+		SetClient(client),
+		SetMiddleware(ClientTrace("example_client"), customMiddleware, InFlight("example_client")),
+	)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	go func() {
+		if err := http.ListenAndServe(":3000", prometheus.Handler()); err != nil {
+			log.Fatalln(err)
+		}
+	}()
+
+	for {
+		select {
+		case <-t.C:
+			log.Println("sending GET")
+			resp, err := promclient.Get("http://example.com")
+			if err != nil {
+				log.Fatalln(err)
+			}
+			resp.Body.Close()
+		}
+	}
+}