add subrouter function to Server (#160)

admin/admin.go

@@ -101,6 +101,23 @@ func (s *Server) AddVersionHandler(version string) {
 	})
 }
 
+// Subrouter creates and returns a subrouter with the specific prefix.
+//
+// The returned subrouter can use middleware without impacting
+// the parent router. For example:
+//
+//     svr := NewServer(":8080")
+//     subRouter := svr.Subrouter("/prefix")
+//     subRouter.Use(someMiddleware)
+//     subRouter.HandleFunc("/resource", ResourceHandler)
+//
+// Here, requests for "/prefix/resource" would go through someMiddleware while
+// the liveliness and readiness routes added to the parent router by NewServer()
+// would not.
+func (s *Server) Subrouter(pathPrefix string) *mux.Router {
+	return s.router.PathPrefix(pathPrefix).Subrouter()
+}
+
 // profileEnabled returns if a given pprof handler should be
 // enabled according to pprofHandlers and the PPROF_* environment
 // variables.

admin/admin_test.go

@@ -8,6 +8,9 @@ import (
 	"io/ioutil"
 	"net/http"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestAdmin__pprof(t *testing.T) {
@@ -146,3 +149,39 @@ func TestAdmin__BindAddr(t *testing.T) {
 		t.Errorf("bogus HTTP status code: %d", resp.StatusCode)
 	}
 }
+
+func TestServer_Subrouter(t *testing.T) {
+	svc := NewServer(":0")
+	subrouter := svc.Subrouter("/sub")
+	subrouter.Use(func(h http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.Write([]byte("middleware\n"))
+			h.ServeHTTP(w, r)
+		})
+	})
+	subrouter.Path("/test").HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("/sub/test"))
+	})
+	go svc.Listen()
+	defer svc.Shutdown()
+
+	// This request is expected to go through the subrouter with its middleware
+	resp, err := http.DefaultClient.Get("http://" + svc.BindAddr() + "/sub/test")
+	require.NoError(t, err)
+	defer resp.Body.Close()
+
+	assert.Equal(t, http.StatusOK, resp.StatusCode)
+	body, err := ioutil.ReadAll(resp.Body)
+	require.NoError(t, err)
+	assert.Equal(t, "middleware\n/sub/test", string(body))
+
+	// This request hits the main router, so should not have a path prefix or middleware
+	liveResponse, err := http.DefaultClient.Get("http://" + svc.BindAddr() + "/live")
+	require.NoError(t, err)
+	defer liveResponse.Body.Close()
+
+	assert.Equal(t, http.StatusOK, liveResponse.StatusCode)
+	liveBody, err := ioutil.ReadAll(liveResponse.Body)
+	require.NoError(t, err)
+	assert.NotContains(t, string(liveBody), "middleware")
+}