springcloud 微服务组件 Hystrix 之源码分析（十五）

我就是我 2022-12-03 09:13 215阅读 0赞

今天我们分析Hystrix 的源码：废话少说，从jar包开始：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70][]

1、点击进入 HystrixCircuitBreakerConfiguration  创建 hystrixCommand 注解的切面类

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 2][]

2、找到HystrixCommand  注解，发现对应业务接口上的注解，说明这个业务类会生成代理

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 3][]

客户端调用主要走这个方法：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 4][]

3、点击CommandExecutor进入：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 5][]

先看同步方法：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 6][]

进入:HystrixCommand 核心类，后面的fegin和zuul 组件都用到这个类，调用同步阻塞方法

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 7][]

点击query方法：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 8][]

点击toObservable方法进入 AbstractCommand 里面有多个匿名内部类，属于Rsjava 代码写法风格

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 9][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 10][]

点击 applyHystrixSemantics 调用匿名类 里面的call方法

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 11][]

进入发现allRequest()方法 是是否允许请求正常的业务方法，此为熔断的功能，比如：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 12][]

4、进入：熔断器是否开启（配置）、是否关闭（配置）、没有开启、允许单个请求；
    
    
    点击isOpen(),最大请求数、错误百分比、原子操作、记录时间；
    
    
    点击allowSingleTest(),单个测试请求 对比时间

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 13][]

返回刚才源代码:

private Observable<R> applyHystrixSemantics(final AbstractCommand<R> _cmd) {
            // mark that we're starting execution on the ExecutionHook
            // if this hook throws an exception, then a fast-fail occurs with no fallback.  No state is left inconsistent
            executionHook.onStart(_cmd);
    
            /* determine if we're allowed to execute */
            if (circuitBreaker.allowRequest()) {
                final TryableSemaphore executionSemaphore = getExecutionSemaphore();//信号量
                final AtomicBoolean semaphoreHasBeenReleased = new AtomicBoolean(false);
                final Action0 singleSemaphoreRelease = new Action0() {
                    @Override
                    public void call() {
                        if (semaphoreHasBeenReleased.compareAndSet(false, true)) {
                            executionSemaphore.release();
                        }
                    }
                };
    
                final Action1<Throwable> markExceptionThrown = new Action1<Throwable>() {
                    @Override
                    public void call(Throwable t) {
                        eventNotifier.markEvent(HystrixEventType.EXCEPTION_THROWN, commandKey);
                    }
                };
    
                if (executionSemaphore.tryAcquire()) {//获取请求
                    try {
                        /* used to track userThreadExecutionTime */
                        executionResult = executionResult.setInvocationStartTime(System.currentTimeMillis());
                        return executeCommandAndObserve(_cmd)//信号量执行的主方法
                                .doOnError(markExceptionThrown)
                                .doOnTerminate(singleSemaphoreRelease)
                                .doOnUnsubscribe(singleSemaphoreRelease);
                    } catch (RuntimeException e) {
                        return Observable.error(e);
                    }
                } else {
                    return handleSemaphoreRejectionViaFallback();//信号量降级方法
                }
            } else {
                return handleShortCircuitViaFallback();//降级方法
            }
        }

5、点击 getExecutionSemaphore  找到信号量配置，和开发代码对比

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 14][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 15][]

信号量的值是否达到最大

点击  executeCommandAndObserve 方法：里面有超时时间设置

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 16][]![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 17][]

点击executeCommandWithSpecifiedIsolation 线程池策略：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 18][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 19][] ctrl+t 对这个方法  getExecutionObservable，找到核心钩子方法

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 20][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 21][] ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 22][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 23][] 5、进入反射调用的方法：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 24][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 25][] 这条核心路执行完了，信号量和线程池策略实现思路大同小异。

点击wrapWithAllOnNextHooks 调用匿名类里面的call方法：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 26][]

3、线程池的创建及超时控制

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 27][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 28][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 29][]

这里创建了线程其他的，比如熔断器开启，线程池，信号量都满了，则会走到降级方法

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 30][]

这里也是会反射调用到 fallback 方法，fallback 降级方法也是有信号量和线程池的大小控制 的，也就是信号量或线程池是多少大小，fallback 降级方法也会接收多少降级的请求。

Hystrix 源码分析结束，明天我们分析Fegin的源码，敬请期待。

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