Stop using the global prometheus registry

Replace usage of the global Prometheus registry with a private registry
object which will be exported under the given prometheus path.

Godeps/Godeps.json

@@ -469,6 +469,11 @@
 			"Comment": "v0.8.0-62-g08fd2e1",
 			"Rev": "08fd2e12372a66e68e30523c7642e0cbc3e4fbde"
 		},
+		{
+			"ImportPath": "github.com/prometheus/client_golang/prometheus/promhttp",
+			"Comment": "v0.8.0-62-g08fd2e1",
+			"Rev": "08fd2e12372a66e68e30523c7642e0cbc3e4fbde"
+		},
 		{
 			"ImportPath": "github.com/prometheus/client_model/go",
 			"Comment": "model-0.0.2-14-g6f38060",

http/handlers.go

@@ -17,6 +17,7 @@ package http
 import (
 	"fmt"
 	"net/http"
+	"os"
 
 	"github.com/google/cadvisor/api"
 	"github.com/google/cadvisor/healthz"
@@ -30,6 +31,7 @@ import (
 	auth "github.com/abbot/go-http-auth"
 	"github.com/golang/glog"
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
 func RegisterHandlers(mux httpmux.Mux, containerManager manager.Manager, httpAuthFile, httpAuthRealm, httpDigestFile, httpDigestRealm string) error {
@@ -54,7 +56,7 @@ func RegisterHandlers(mux httpmux.Mux, containerManager manager.Manager, httpAut
 	// Redirect / to containers page.
 	mux.Handle("/", http.RedirectHandler(pages.ContainersPage, http.StatusTemporaryRedirect))
 
-	var authenticated bool = false
+	var authenticated bool
 
 	// Setup the authenticator object
 	if httpAuthFile != "" {
@@ -89,13 +91,16 @@ func RegisterHandlers(mux httpmux.Mux, containerManager manager.Manager, httpAut
 	return nil
 }
 
-// RegisterPrometheusHandler creates a new PrometheusCollector, registers it
+// RegisterPrometheusHandler creates a new PrometheusCollector and configures
-// on the global registry and configures the provided HTTP mux to handle the
+// the provided HTTP mux to handle the given Prometheus endpoint.
-// given Prometheus endpoint.
 func RegisterPrometheusHandler(mux httpmux.Mux, containerManager manager.Manager, prometheusEndpoint string, f metrics.ContainerLabelsFunc) {
-	collector := metrics.NewPrometheusCollector(containerManager, f)
+	r := prometheus.NewRegistry()
-	prometheus.MustRegister(collector)
+	r.MustRegister(
-	mux.Handle(prometheusEndpoint, prometheus.Handler())
+		metrics.NewPrometheusCollector(containerManager, f),
+		prometheus.NewGoCollector(),
+		prometheus.NewProcessCollector(os.Getpid(), ""),
+	)
+	mux.Handle(prometheusEndpoint, promhttp.HandlerFor(r, promhttp.HandlerOpts{}))
 }
 
 func staticHandlerNoAuth(w http.ResponseWriter, r *http.Request) {

vendor/github.com/prometheus/client_golang/prometheus/promhttp/http.go

@@ -0,0 +1,201 @@
+// 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 contains functions to create http.Handler instances to
+// expose Prometheus metrics via HTTP. In later versions of this package, it
+// will also contain tooling to instrument instances of http.Handler and
+// http.RoundTripper.
+//
+// promhttp.Handler acts on the prometheus.DefaultGatherer. With HandlerFor,
+// you can create a handler for a custom registry or anything that implements
+// the Gatherer interface. It also allows to create handlers that act
+// differently on errors or allow to log errors.
+package promhttp
+
+import (
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"sync"
+
+	"github.com/prometheus/common/expfmt"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const (
+	contentTypeHeader     = "Content-Type"
+	contentLengthHeader   = "Content-Length"
+	contentEncodingHeader = "Content-Encoding"
+	acceptEncodingHeader  = "Accept-Encoding"
+)
+
+var bufPool sync.Pool
+
+func getBuf() *bytes.Buffer {
+	buf := bufPool.Get()
+	if buf == nil {
+		return &bytes.Buffer{}
+	}
+	return buf.(*bytes.Buffer)
+}
+
+func giveBuf(buf *bytes.Buffer) {
+	buf.Reset()
+	bufPool.Put(buf)
+}
+
+// Handler returns an HTTP handler for the prometheus.DefaultGatherer. The
+// Handler uses the default HandlerOpts, i.e. report the first error as an HTTP
+// error, no error logging, and compression if requested by the client.
+//
+// If you want to create a Handler for the DefaultGatherer with different
+// HandlerOpts, create it with HandlerFor with prometheus.DefaultGatherer and
+// your desired HandlerOpts.
+func Handler() http.Handler {
+	return HandlerFor(prometheus.DefaultGatherer, HandlerOpts{})
+}
+
+// HandlerFor returns an http.Handler for the provided Gatherer. The behavior
+// of the Handler is defined by the provided HandlerOpts.
+func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		mfs, err := reg.Gather()
+		if err != nil {
+			if opts.ErrorLog != nil {
+				opts.ErrorLog.Println("error gathering metrics:", err)
+			}
+			switch opts.ErrorHandling {
+			case PanicOnError:
+				panic(err)
+			case ContinueOnError:
+				if len(mfs) == 0 {
+					http.Error(w, "No metrics gathered, last error:\n\n"+err.Error(), http.StatusInternalServerError)
+					return
+				}
+			case HTTPErrorOnError:
+				http.Error(w, "An error has occurred during metrics gathering:\n\n"+err.Error(), http.StatusInternalServerError)
+				return
+			}
+		}
+
+		contentType := expfmt.Negotiate(req.Header)
+		buf := getBuf()
+		defer giveBuf(buf)
+		writer, encoding := decorateWriter(req, buf, opts.DisableCompression)
+		enc := expfmt.NewEncoder(writer, contentType)
+		var lastErr error
+		for _, mf := range mfs {
+			if err := enc.Encode(mf); err != nil {
+				lastErr = err
+				if opts.ErrorLog != nil {
+					opts.ErrorLog.Println("error encoding metric family:", err)
+				}
+				switch opts.ErrorHandling {
+				case PanicOnError:
+					panic(err)
+				case ContinueOnError:
+					// Handled later.
+				case HTTPErrorOnError:
+					http.Error(w, "An error has occurred during metrics encoding:\n\n"+err.Error(), http.StatusInternalServerError)
+					return
+				}
+			}
+		}
+		if closer, ok := writer.(io.Closer); ok {
+			closer.Close()
+		}
+		if lastErr != nil && buf.Len() == 0 {
+			http.Error(w, "No metrics encoded, last error:\n\n"+err.Error(), http.StatusInternalServerError)
+			return
+		}
+		header := w.Header()
+		header.Set(contentTypeHeader, string(contentType))
+		header.Set(contentLengthHeader, fmt.Sprint(buf.Len()))
+		if encoding != "" {
+			header.Set(contentEncodingHeader, encoding)
+		}
+		w.Write(buf.Bytes())
+		// TODO(beorn7): Consider streaming serving of metrics.
+	})
+}
+
+// HandlerErrorHandling defines how a Handler serving metrics will handle
+// errors.
+type HandlerErrorHandling int
+
+// These constants cause handlers serving metrics to behave as described if
+// errors are encountered.
+const (
+	// Serve an HTTP status code 500 upon the first error
+	// encountered. Report the error message in the body.
+	HTTPErrorOnError HandlerErrorHandling = iota
+	// Ignore errors and try to serve as many metrics as possible.  However,
+	// if no metrics can be served, serve an HTTP status code 500 and the
+	// last error message in the body. Only use this in deliberate "best
+	// effort" metrics collection scenarios. It is recommended to at least
+	// log errors (by providing an ErrorLog in HandlerOpts) to not mask
+	// errors completely.
+	ContinueOnError
+	// Panic upon the first error encountered (useful for "crash only" apps).
+	PanicOnError
+)
+
+// Logger is the minimal interface HandlerOpts needs for logging. Note that
+// log.Logger from the standard library implements this interface, and it is
+// easy to implement by custom loggers, if they don't do so already anyway.
+type Logger interface {
+	Println(v ...interface{})
+}
+
+// HandlerOpts specifies options how to serve metrics via an http.Handler. The
+// zero value of HandlerOpts is a reasonable default.
+type HandlerOpts struct {
+	// ErrorLog specifies an optional logger for errors collecting and
+	// serving metrics. If nil, errors are not logged at all.
+	ErrorLog Logger
+	// ErrorHandling defines how errors are handled. Note that errors are
+	// logged regardless of the configured ErrorHandling provided ErrorLog
+	// is not nil.
+	ErrorHandling HandlerErrorHandling
+	// If DisableCompression is true, the handler will never compress the
+	// response, even if requested by the client.
+	DisableCompression bool
+}
+
+// decorateWriter wraps a writer to handle gzip compression if requested.  It
+// returns the decorated writer and the appropriate "Content-Encoding" header
+// (which is empty if no compression is enabled).
+func decorateWriter(request *http.Request, writer io.Writer, compressionDisabled bool) (io.Writer, string) {
+	if compressionDisabled {
+		return writer, ""
+	}
+	header := request.Header.Get(acceptEncodingHeader)
+	parts := strings.Split(header, ",")
+	for _, part := range parts {
+		part := strings.TrimSpace(part)
+		if part == "gzip" || strings.HasPrefix(part, "gzip;") {
+			return gzip.NewWriter(writer), "gzip"
+		}
+	}
+	return writer, ""
+}