Move packages to proejct/pkg to follow go project folder structure convention (#1190)

pkg/router/mutablemux.go

@@ -0,0 +1,57 @@
+/*
+Copyright 2016 The Fission Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package router
+
+import (
+	"net/http"
+	"sync/atomic"
+
+	"github.com/gorilla/mux"
+	"go.uber.org/zap"
+)
+
+//
+// mutableRouter wraps the mux router, and allows the router to be
+// atomically changed.
+//
+
+type mutableRouter struct {
+	logger *zap.Logger
+	router atomic.Value // mux.Router
+}
+
+func NewMutableRouter(logger *zap.Logger, handler *mux.Router) *mutableRouter {
+	mr := mutableRouter{
+		logger: logger.Named("mutable_router"),
+	}
+	mr.router.Store(handler)
+	return &mr
+}
+
+func (mr *mutableRouter) ServeHTTP(responseWriter http.ResponseWriter, request *http.Request) {
+	// Atomically grab the underlying mux router and call it.
+	routerValue := mr.router.Load()
+	router, ok := routerValue.(*mux.Router)
+	if !ok {
+		mr.logger.Panic("invalid router type")
+	}
+	router.ServeHTTP(responseWriter, request)
+}
+
+func (mr *mutableRouter) updateRouter(newHandler *mux.Router) {
+	mr.router.Store(newHandler)
+}