Merge pull request #1660 from alileza/add_http_errorlog

Log HTTP server errors using common/log

vendor/github.com/prometheus/common/log/log.go

@@ -16,6 +16,7 @@ package log
 import (
 	"flag"
 	"fmt"
+	"log"
 	"net/url"
 	"os"
 	"runtime"
@@ -302,3 +303,16 @@ func Fatalln(args ...interface{}) {
 func Fatalf(format string, args ...interface{}) {
 	baseLogger.sourced().Fatalf(format, args...)
 }
+
+type errorLogWriter struct{}
+
+func (errorLogWriter) Write(b []byte) (int, error) {
+	baseLogger.sourced().Error(string(b))
+	return len(b), nil
+}
+
+// NewErrorLogger returns a log.Logger that is meant to be used
+// in the ErrorLog field of an http.Server to log HTTP server errors.
+func NewErrorLogger() *log.Logger {
+	return log.New(&errorLogWriter{}, "", 0)
+}

vendor/vendor.json

@@ -173,10 +173,10 @@
 			"revisionTime": "2016-05-19T16:20:33Z"
 		},
 		{
-			"checksumSHA1": "koBNYQryxAG8hyHBlpn8pcnSVdM=",
+			"checksumSHA1": "qHoBp/PVBcLedTNZrF3toV9QGa0=",
 			"path": "github.com/prometheus/common/log",
-			"revision": "c16e34897a744c32f6733ee720e60c4de13887fb",
-			"revisionTime": "2016-05-19T16:20:33Z"
+			"revision": "a6ab08426bb262e2d190097751f5cfd1cfdfd17d",
+			"revisionTime": "2016-05-26T15:55:09Z"
 		},
 		{
 			"checksumSHA1": "Zgmg/aOfoCNTAMtrXqBJmt852t0=",

web/web.go

@@ -239,7 +239,12 @@ func (h *Handler) Reload() <-chan struct{} {
 // Run serves the HTTP endpoints.
 func (h *Handler) Run() {
 	log.Infof("Listening on %s", h.options.ListenAddress)
-	h.listenErrCh <- http.ListenAndServe(h.options.ListenAddress, h.router)
+	server := &http.Server{
+		Addr:     h.options.ListenAddress,
+		Handler:  h.router,
+		ErrorLog: log.NewErrorLogger(),
+	}
+	h.listenErrCh <- server.ListenAndServe()
 }
 
 func (h *Handler) alerts(w http.ResponseWriter, r *http.Request) {