Add -metrics-path flag for configuring the metrics endpoint

Addresses #52

cmd/tusd/cli/flags.go

@@ -17,6 +17,7 @@ var Flags struct {
 	HooksDir      string
 	ShowVersion   bool
 	ExposeMetrics bool
+	MetricsPath   string
 	BehindProxy   bool
 
 	HooksInstalled bool
@@ -34,6 +35,7 @@ func ParseFlags() {
 	flag.StringVar(&Flags.HooksDir, "hooks-dir", "", "Directory to search for available hooks scripts")
 	flag.BoolVar(&Flags.ShowVersion, "version", false, "Print tusd version information")
 	flag.BoolVar(&Flags.ExposeMetrics, "expose-metrics", true, "Expose metrics about tusd usage")
+	flag.StringVar(&Flags.MetricsPath, "metrics-path", "/metrics", "Path under which the metrics endpoint will be accessible")
 	flag.BoolVar(&Flags.BehindProxy, "behind-proxy", false, "Respect X-Forwarded-* and similar headers which may be set by proxies")
 
 	flag.Parse()

cmd/tusd/cli/metrics.go

@@ -18,5 +18,6 @@ func SetupMetrics(handler *tusd.Handler) {
 	prometheus.MustRegister(MetricsOpenConnections)
 	prometheus.MustRegister(prometheuscollector.New(handler.Metrics))
 
-	http.Handle("/metrics", prometheus.Handler())
+	stdout.Printf("Using %s as the metrics path.\n", Flags.MetricsPath)
+	http.Handle(Flags.MetricsPath, prometheus.Handler())
 }

cmd/tusd/cli/serve.go

@@ -27,7 +27,6 @@ func Serve() {
 
 	stdout.Printf("Using %s as address to listen.\n", address)
 	stdout.Printf("Using %s as the base path.\n", basepath)
-	stdout.Printf(Composer.Capabilities())
 
 	SetupPostHooks(handler)
 
@@ -35,6 +34,8 @@ func Serve() {
 		SetupMetrics(handler)
 	}
 
+	stdout.Printf(Composer.Capabilities())
+
 	// Do not display the greeting if the tusd handler will be mounted at the root
 	// path. Else this would cause a "multiple registrations for /" panic.
 	if basepath != "/" {