| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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 pkg |
| |
| import ( |
| "errors" |
| "sync" |
| ) |
| |
| import ( |
| "github.com/apache/dubbo-go/common" |
| "github.com/apache/dubbo-go/common/extension" |
| "github.com/apache/dubbo-go/common/logger" |
| "github.com/apache/dubbo-go/filter" |
| "github.com/apache/dubbo-go/protocol" |
| ) |
| |
| func init() { |
| /* |
| * register your custom implementation into filter. |
| * "DefaultValueHandler" is the name used in configure file, like server.yml: |
| * "UserProvider": |
| * registry: "hangzhouzk" |
| * protocol : "dubbo" |
| * interface : "com.ikurento.user.UserProvider" |
| * ... # other configuration |
| * tps.limiter: "method-service", |
| * |
| * tps.limit.rejected.handler: "DefaultValueHandler", |
| * So when the invocation is over the tps limitation, it will return the default value. |
| * This is a common use case. |
| */ |
| extension.SetRejectedExecutionHandler("DefaultValueHandler", GetDefaultValueRejectedExecutionHandlerSingleton) |
| |
| } |
| |
| /** |
| * The RejectedExecutionHandler is used by some components, |
| * e.g, ExecuteLimitFilter, GracefulShutdownFilter, TpsLimitFilter. |
| * When the requests are rejected, the RejectedExecutionHandler allows you to do something. |
| * You can alert the developer, or redirect those requests to another providers. It depends on what you need. |
| * |
| * Let's assume that you need a RejectedExecutionHandler which will return some default result if the request was rejected. |
| */ |
| type DefaultValueRejectedExecutionHandler struct { |
| defaultResult sync.Map |
| } |
| |
| func (mh *DefaultValueRejectedExecutionHandler) RejectedExecution(url *common.URL, invocation protocol.Invocation) protocol.Result { |
| // put your custom business here. |
| logger.Error("Here is my custom rejected handler. I want to do something if the requests are rejected. ") |
| // in most cases, if the request was rejected, you won't want to invoke the origin provider. |
| // But if you really want to do that, you can do it like this: |
| // invocation.Invoker().Invoke(invocation) |
| |
| // the ServiceKey + methodName is the key |
| key := url.ServiceKey() + "#" + invocation.MethodName() |
| result, loaded := mh.defaultResult.Load(key) |
| if !loaded { |
| // we didn't configure any default value for this invocation |
| return &protocol.RPCResult{ |
| Err: errors.New("The request is rejected and doesn't have any default value. "), |
| } |
| } |
| return result.(*protocol.RPCResult) |
| } |
| |
| func GetCustomRejectedExecutionHandler() filter.RejectedExecutionHandler { |
| return &DefaultValueRejectedExecutionHandler{} |
| } |
| |
| var ( |
| customHandlerOnce sync.Once |
| customHandlerInstance *DefaultValueRejectedExecutionHandler |
| ) |
| |
| /** |
| * the better way is designing the RejectedExecutionHandler as singleton. |
| */ |
| func GetDefaultValueRejectedExecutionHandlerSingleton() filter.RejectedExecutionHandler { |
| customHandlerOnce.Do(func() { |
| customHandlerInstance = &DefaultValueRejectedExecutionHandler{} |
| }) |
| |
| initDefaultValue() |
| |
| return customHandlerInstance |
| } |
| |
| func initDefaultValue() { |
| // setting your default value |
| } |