route: support for instrumentation

route/route.go

@@ -19,11 +19,12 @@ func WithParam(ctx context.Context, p, v string) context.Context {
 	return context.WithValue(ctx, param(p), v)
 }
 
-// Router wraps httprouter.Router and adds support for prefixed sub-routers
-// and per-request context injections.
+// Router wraps httprouter.Router and adds support for prefixed sub-routers,
+// per-request context injections and instrumentation.
 type Router struct {
 	rtr    *httprouter.Router
 	prefix string
+	instrh func(handlerName string, handler http.HandlerFunc) http.HandlerFunc
 }
 
 // New returns a new Router.
@@ -33,47 +34,55 @@ func New() *Router {
 	}
 }
 
+// WithInstrumentation returns a router with instrumentation support.
+func (r *Router) WithInstrumentation(instrh func(handlerName string, handler http.HandlerFunc) http.HandlerFunc) *Router {
+	return &Router{rtr: r.rtr, prefix: r.prefix, instrh: instrh}
+}
+
 // WithPrefix returns a router that prefixes all registered routes with prefix.
 func (r *Router) WithPrefix(prefix string) *Router {
-	return &Router{rtr: r.rtr, prefix: r.prefix + prefix}
+	return &Router{rtr: r.rtr, prefix: r.prefix + prefix, instrh: r.instrh}
 }
 
 // handle turns a HandlerFunc into an httprouter.Handle.
-func (r *Router) handle(h http.HandlerFunc) httprouter.Handle {
+func (r *Router) handle(handlerName string, h http.HandlerFunc) httprouter.Handle {
 	return func(w http.ResponseWriter, req *http.Request, params httprouter.Params) {
 		ctx, cancel := context.WithCancel(req.Context())
 		defer cancel()
 
 		for _, p := range params {
 			ctx = context.WithValue(ctx, param(p.Key), p.Value)
 		}
+		if r.instrh != nil {
+			h = r.instrh(handlerName, h)
+		}
 		h(w, req.WithContext(ctx))
 	}
 }
 
 // Get registers a new GET route.
 func (r *Router) Get(path string, h http.HandlerFunc) {
-	r.rtr.GET(r.prefix+path, r.handle(h))
+	r.rtr.GET(r.prefix+path, r.handle(path, h))
 }
 
 // Options registers a new OPTIONS route.
 func (r *Router) Options(path string, h http.HandlerFunc) {
-	r.rtr.OPTIONS(r.prefix+path, r.handle(h))
+	r.rtr.OPTIONS(r.prefix+path, r.handle(path, h))
 }
 
 // Del registers a new DELETE route.
 func (r *Router) Del(path string, h http.HandlerFunc) {
-	r.rtr.DELETE(r.prefix+path, r.handle(h))
+	r.rtr.DELETE(r.prefix+path, r.handle(path, h))
 }
 
 // Put registers a new PUT route.
 func (r *Router) Put(path string, h http.HandlerFunc) {
-	r.rtr.PUT(r.prefix+path, r.handle(h))
+	r.rtr.PUT(r.prefix+path, r.handle(path, h))
 }
 
 // Post registers a new POST route.
 func (r *Router) Post(path string, h http.HandlerFunc) {
-	r.rtr.POST(r.prefix+path, r.handle(h))
+	r.rtr.POST(r.prefix+path, r.handle(path, h))
 }
 
 // Redirect takes an absolute path and sends an internal HTTP redirect for it,

route/route_test.go

@@ -42,3 +42,35 @@ func TestContext(t *testing.T) {
 	}
 	router.ServeHTTP(nil, r)
 }
+
+func TestInstrumentation(t *testing.T) {
+	var got string
+	cases := []struct {
+		router *Router
+		want   string
+	}{
+		{
+			router: New(),
+			want:   "",
+		}, {
+			router: New().WithInstrumentation(func(handlerName string, handler http.HandlerFunc) http.HandlerFunc {
+				got = handlerName
+				return handler
+			}),
+			want: "/foo",
+		},
+	}
+
+	for _, c := range cases {
+		c.router.Get("/foo", func(w http.ResponseWriter, r *http.Request) {})
+
+		r, err := http.NewRequest("GET", "http://localhost:9090/foo", nil)
+		if err != nil {
+			t.Fatalf("Error building test request: %s", err)
+		}
+		c.router.ServeHTTP(nil, r)
+		if c.want != got {
+			t.Fatalf("Unexpected value: want %q, got %q", c.want, got)
+		}
+	}
+}