server: add a healthcheck route at /_internal/healthcheck

Closes #904.

fakestorage/server.go

@@ -215,6 +215,9 @@ func (s *Server) buildMuxer() {
 	const apiPrefix = "/storage/v1"
 	s.mux = mux.NewRouter()
 
+	// healthcheck
+	s.mux.Path("/_internal/healthcheck").Methods(http.MethodGet).HandlerFunc(s.healthcheck)
+
 	routers := []*mux.Router{
 		s.mux.PathPrefix(apiPrefix).Subrouter(),
 		s.mux.MatcherFunc(s.publicHostMatcher).PathPrefix(apiPrefix).Subrouter(),
@@ -268,6 +271,10 @@ func (s *Server) buildMuxer() {
 	s.mux.Host("{bucketName:.+}").Path("/{objectName:.+}").Methods(http.MethodPost, http.MethodPut).HandlerFunc(jsonToHTTPHandler(s.insertObject))
 }
 
+func (s *Server) healthcheck(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusOK)
+}
+
 // publicHostMatcher matches incoming requests against the currently specified server publicHost.
 func (s *Server) publicHostMatcher(r *http.Request, rm *mux.RouteMatch) bool {
 	if strings.Contains(s.publicHost, ":") || !strings.Contains(r.Host, ":") {