Add middleware for logging each request to the app.

common/middleware/logging.go

@@ -0,0 +1,45 @@
+package middleware
+
+import (
+	"bufio"
+	"fmt"
+	"net"
+	"net/http"
+	"time"
+
+	log "github.com/Sirupsen/logrus"
+)
+
+// Logging middleware logs each HTTP request method, path, response code and duration.
+var Logging = Func(func(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		begin := time.Now()
+		i := &interceptor{ResponseWriter: w, statusCode: http.StatusOK}
+		next.ServeHTTP(i, r)
+		log.Infof("%s %s (%d) %s", r.Method, r.RequestURI, i.statusCode, time.Since(begin))
+	})
+})
+
+// interceptor implements WriteHeader to intercept status codes. WriteHeader
+// may not be called on success, so initialize statusCode with the status you
+// want to report on success, i.e. http.StatusOK.
+//
+// interceptor also implements net.Hijacker, to let the downstream Handler
+// hijack the connection. This is needed by the app-mapper's proxy.
+type interceptor struct {
+	http.ResponseWriter
+	statusCode int
+}
+
+func (i *interceptor) WriteHeader(code int) {
+	i.statusCode = code
+	i.ResponseWriter.WriteHeader(code)
+}
+
+func (i *interceptor) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	hj, ok := i.ResponseWriter.(http.Hijacker)
+	if !ok {
+		return nil, nil, fmt.Errorf("interceptor: can't cast parent ResponseWriter to Hijacker")
+	}
+	return hj.Hijack()
+}

common/middleware/middleware.go

@@ -0,0 +1,30 @@
+package middleware
+
+import (
+	"net/http"
+)
+
+// Interface is the shared contract for all middlesware, and allows middlesware
+// to wrap handlers.
+type Interface interface {
+	Wrap(http.Handler) http.Handler
+}
+
+// Func is to Interface as http.HandlerFunc is to http.Handler
+type Func func(http.Handler) http.Handler
+
+// Wrap implements Interface
+func (m Func) Wrap(next http.Handler) http.Handler {
+	return m(next)
+}
+
+// Merge produces a middleware that applies multiple middlesware in turn;
+// ie Merge(f,g,h).Wrap(handler) == f.Wrap(g.Wrap(h.Wrap(handler)))
+func Merge(middlesware ...Interface) Interface {
+	return Func(func(next http.Handler) http.Handler {
+		for i := len(middlesware) - 1; i >= 0; i-- {
+			next = middlesware[i].Wrap(next)
+		}
+		return next
+	})
+}

prog/app.go

@@ -20,6 +20,7 @@ import (
 
 	"github.com/weaveworks/scope/app"
 	"github.com/weaveworks/scope/app/multitenant"
+	"github.com/weaveworks/scope/common/middleware"
 	"github.com/weaveworks/scope/common/weave"
 	"github.com/weaveworks/scope/common/xfer"
 	"github.com/weaveworks/scope/probe/docker"
@@ -110,10 +111,11 @@ func pipeRouterFactory(userIDer multitenant.UserIDer, pipeRouterURL, consulInf s
 // Main runs the app
 func appMain() {
 	var (
-		window    = flag.Duration("window", 15*time.Second, "window")
-		listen    = flag.String("http.address", ":"+strconv.Itoa(xfer.AppPort), "webserver listen address")
-		logLevel  = flag.String("log.level", "info", "logging threshold level: debug|info|warn|error|fatal|panic")
-		logPrefix = flag.String("log.prefix", "<app>", "prefix for each log line")
+		window      = flag.Duration("window", 15*time.Second, "window")
+		listen      = flag.String("http.address", ":"+strconv.Itoa(xfer.AppPort), "webserver listen address")
+		logLevel    = flag.String("log.level", "info", "logging threshold level: debug|info|warn|error|fatal|panic")
+		logPrefix   = flag.String("log.prefix", "<app>", "prefix for each log line")
+		logRequests = flag.Bool("log.requests", false, "Log individual HTTP requests")
 
 		weaveAddr      = flag.String("weave.addr", app.DefaultWeaveURL, "Address on which to contact WeaveDNS")
 		weaveHostname  = flag.String("weave.hostname", app.DefaultHostname, "Hostname to advertise in WeaveDNS")
@@ -189,6 +191,9 @@ func appMain() {
 	}
 
 	handler := router(collector, controlRouter, pipeRouter)
+	if *logRequests {
+		handler = middleware.Logging.Wrap(handler)
+	}
 	go func() {
 		log.Infof("listening on %s", *listen)
 		log.Info(http.ListenAndServe(*listen, handler))