Update logging middleware to log in apache common format

middlewares.go

@@ -2,15 +2,59 @@ package main
 
 import (
 	"fmt"
+	"net"
 	"net/http"
 	"os"
+	"strconv"
 	"time"
 )
 
+// A responseRecorderWriter records response status and size.
+// It implements http.ResponseWriter interface.
+type responseRecorderWriter struct {
+	http.ResponseWriter
+	// The status code that the server sends back to the client.
+	status int
+	// The size of the object returned to the client, not including the response headers.
+	size int
+}
+
+func (w *responseRecorderWriter) WriteHeader(status int) {
+	w.ResponseWriter.WriteHeader(status)
+	w.status = status
+}
+
+func (w *responseRecorderWriter) Write(b []byte) (int, error) {
+	// If WriteHeader is not called explicitly, the first call to Write
+	// will trigger an implicit WriteHeader(http.StatusOK).
+	if w.status == 0 {
+		w.status = http.StatusOK
+	}
+	n, err := w.ResponseWriter.Write(b)
+	w.size += n
+	return n, err
+}
+
 func loggingMiddleware(h http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		fmt.Fprintf(os.Stdout, "%v \"%s %s\"\n",
-			time.Now().Format(time.RFC3339), r.Method, r.URL)
-		h.ServeHTTP(w, r)
+		rw := &responseRecorderWriter{ResponseWriter: w}
+		h.ServeHTTP(rw, r)
+
+		host, _, err := net.SplitHostPort(r.RemoteAddr)
+		if err != nil {
+			host = r.RemoteAddr
+		}
+		username := "-"
+		if user := r.URL.User; user != nil {
+			username = user.Username()
+		}
+		size := "-"
+		if rw.size > 0 {
+			size = strconv.Itoa(rw.size)
+		}
+		// Write a log in Apache common log format (http://httpd.apache.org/docs/2.2/logs.html#common).
+		fmt.Fprintf(os.Stdout, "%s - %s [%s] \"%s %s %s\" %d %s\n",
+			host, username, time.Now().Format("02/Jan/2006:15:04:05 -0700"),
+			r.Method, r.URL, r.Proto, rw.status, size)
 	})
 }