wu-sheng commented on a change in pull request #4857: URL: https://github.com/apache/skywalking/pull/4857#discussion_r435277498
########## File path: apm-sniffer/apm-sdk-plugin/hystrix-1.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/hystrix/v1/SWHystrixLifecycleForwardingRequestVariable.java ########## @@ -0,0 +1,84 @@ +/* + * 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 org.apache.skywalking.apm.plugin.hystrix.v1; + +import com.netflix.hystrix.strategy.concurrency.HystrixRequestContext; +import com.netflix.hystrix.strategy.concurrency.HystrixRequestVariable; +import com.netflix.hystrix.strategy.concurrency.HystrixRequestVariableDefault; +import com.netflix.hystrix.strategy.concurrency.HystrixRequestVariableLifecycle; +import com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategy; + +/** + * Implementation of {@link HystrixRequestVariable} which forwards to the wrapped + * {@link HystrixRequestVariableLifecycle}. + * <p> + * This implementation also returns null when {@link #get()} is called while the {@link HystrixRequestContext} has not + * been initialized rather than throwing an exception, allowing for use in a {@link HystrixConcurrencyStrategy} which + * does not depend on an a HystrixRequestContext + */ +public class SWHystrixLifecycleForwardingRequestVariable<T> extends HystrixRequestVariableDefault<T> { + private final HystrixRequestVariableLifecycle<T> lifecycle; + + /** + * Creates a HystrixRequestVariable which will return data as provided by the {@link HystrixRequestVariableLifecycle} + * + * @param lifecycle lifecycle used to provide values. Must have the same type parameter as the constructed instance. + */ + public SWHystrixLifecycleForwardingRequestVariable(HystrixRequestVariableLifecycle<T> lifecycle) { + this.lifecycle = lifecycle; + } + + /** + * Delegates to the wrapped {@link HystrixRequestVariableLifecycle} + * + * @return T with initial value or null if none. + */ + @Override + public T initialValue() { + return lifecycle.initialValue(); + } + + /** + * Delegates to the wrapped {@link HystrixRequestVariableLifecycle} + * + * @param value of request variable to allow cleanup activity. + * <p> + * If nothing needs to be cleaned up then nothing needs to be done in this method. + */ + @Override + public void shutdown(T value) { + lifecycle.shutdown(value); + } + + /** + * Return null if the {@link HystrixRequestContext} has not been initialized for the current thread. + * <p> + * If {@link HystrixRequestContext} has been initialized then call method in superclass: + * {@link HystrixRequestVariableDefault#get()} + */ + @Override + public T get() { + if (!HystrixRequestContext.isCurrentThreadInitialized()) { + return null; + } + return super.get(); Review comment: Then, why don't we change the SkyWalking wrapper logic? It seems more reasonable, right? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
