一、maven配置

引入feign默認會依賴hystrix，只要不排除就行。 <dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-feign</artifactId> <!-- <exclusions>--> <!-- <exclusion>--> <!-- <groupId>io.github.openfeign</groupId>--> <!-- <artifactId>feign-hystrix</artifactId>--> <!-- </exclusion>--> <!-- </exclusions>--></dependency>

application配置開啟feign的hystrix配置。

feign.hystrix.enabled=true

二、還是上文那個例子，測試

看到代理對象變為HystrixInvocationHandler,

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接著往下調，后面跟單獨的feign一樣。只是在feignHandler上做了一個包裝。

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?這里要注意，這個線程不是TOMCAT的工作線程，而是使用hystrix中的隔離任務線程池中執行。

正常的線程如下為nio-execute-真正的feign遠程接口調用是在hystrix的線程池中。HystrixInvocationHandler.invoke方法為代理方法，最終調用到hystrixCommand.execute()

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@Overridepublic Object invoke(final Object proxy, final Method method, final Object[] args)throws Throwable {// early exit if the invoked method is from java.lang.Object// code is the same as ReflectiveFeign.FeignInvocationHandlerif ("equals".equals(method.getName())) {try {Object otherHandler =args.length > 0 && args[0] != null ? Proxy.getInvocationHandler(args[0]) : null;return equals(otherHandler);} catch (IllegalArgumentException e) {return false;}} else if ("hashCode".equals(method.getName())) {return hashCode();} else if ("toString".equals(method.getName())) {return toString();}HystrixCommand<Object> hystrixCommand = new HystrixCommand<Object>(setterMethodMap.get(method)) {@Overrideprotected Object run() throws Exception {try {return HystrixInvocationHandler.this.dispatch.get(method).invoke(args);} catch (Exception e) {throw e;} catch (Throwable t) {throw (Error) t;}}@Overrideprotected Object getFallback() {if (fallbackFactory == null) {return super.getFallback();}try {Object fallback = fallbackFactory.create(getFailedExecutionException());Object result = fallbackMethodMap.get(method).invoke(fallback, args);if (isReturnsHystrixCommand(method)) {return ((HystrixCommand) result).execute();} else if (isReturnsObservable(method)) {// Create a cold Observablereturn ((Observable) result).toBlocking().first();} else if (isReturnsSingle(method)) {// Create a cold Observable as a Singlereturn ((Single) result).toObservable().toBlocking().first();} else if (isReturnsCompletable(method)) {((Completable) result).await();return null;} else {return result;}} catch (IllegalAccessException e) {// shouldn't happen as method is public due to being an interfacethrow new AssertionError(e);} catch (InvocationTargetException e) {// Exceptions on fallback are tossed by Hystrixthrow new AssertionError(e.getCause());}}};if (isReturnsHystrixCommand(method)) {return hystrixCommand;} else if (isReturnsObservable(method)) {// Create a cold Observablereturn hystrixCommand.toObservable();} else if (isReturnsSingle(method)) {// Create a cold Observable as a Singlereturn hystrixCommand.toObservable().toSingle();} else if (isReturnsCompletable(method)) {return hystrixCommand.toObservable().toCompletable();}return hystrixCommand.execute();}

hystrixCommand.execute()，這個就是進入隊列，然后在隊列進行執行，同步等待。

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