HystrixPlugins

　　获取并发相关类（HystrixConcurrencyStrategy）、事件通知类（HystrixEventNotifier）、度量信息类（HystrixMetricsPublisher）、Properties配置类（HystrixPropertiesStrategy）、HystrixCommand回调函数类（HystrixCommandExecutionHook）、HystrixDynamicProperties，6类插件。

插件获取：

　　HystrixPlugins 首先会去properties（HystrixDynamicProperties）配置下需找相应类型的实现类。

private static 
    
      T getPluginImplementationViaProperties(Class
     
       pluginClass, HystrixDynamicProperties dynamicProperties) {        String classSimpleName = pluginClass.getSimpleName();        // Check Archaius for plugin class.        String propertyName = "hystrix.plugin." + classSimpleName + ".implementation";        String implementingClass = dynamicProperties.getString(propertyName, null).get();        ....
     
    

　　如果返回null，则通过ServiceLoader获取相应类型的实现类。

private 
    
      T getPluginImplementation(Class
     
       pluginClass) {        T p = getPluginImplementationViaProperties(pluginClass, dynamicProperties);        if (p != null) return p;                return findService(pluginClass, classLoader);    }    private static 
      
        T findService(            Class
       
         spi,             ClassLoader classLoader) throws ServiceConfigurationError {                ServiceLoader
        
          sl = ServiceLoader.load(spi,                classLoader);        for (T s : sl) {            if (s != null)                return s;        }        return null;    }
        
       
      
     
    

　　如果获取成功，存储变量中。

final AtomicReference
    
      notifier = new AtomicReference
     
      ();public HystrixEventNotifier getEventNotifier() {        if (notifier.get() == null) {            // check for an implementation from Archaius first            Object impl = getPluginImplementation(HystrixEventNotifier.class);            if (impl == null) {                // nothing set via Archaius so initialize with default                notifier.compareAndSet(null, HystrixEventNotifierDefault.getInstance());                // we don't return from here but call get() again in case of thread-race so the winner will always get returned            } else {                // we received an implementation from Archaius so use it                notifier.compareAndSet(null, (HystrixEventNotifier) impl);            }        }        return notifier.get();    }
     
    

　　获取HystrixDynamicProperties对象，有点不同，首先使用HystrixDynamicPropertiesSystemProperties配置来需找相应类型的实现类。第二如果查询不同会默认使用Archaius，如果依然没有Archaius支持，会使用HystrixDynamicPropertiesSystemProperties。

private static HystrixDynamicProperties resolveDynamicProperties(ClassLoader classLoader, LoggerSupplier logSupplier) {        HystrixDynamicProperties hp = getPluginImplementationViaProperties(HystrixDynamicProperties.class,                 HystrixDynamicPropertiesSystemProperties.getInstance());        if (hp != null) {            logSupplier.getLogger().debug(                    "Created HystrixDynamicProperties instance from System property named "                    + "\"hystrix.plugin.HystrixDynamicProperties.implementation\". Using class: {}",                     hp.getClass().getCanonicalName());            return hp;        }        hp = findService(HystrixDynamicProperties.class, classLoader);        if (hp != null) {            logSupplier.getLogger()                    .debug("Created HystrixDynamicProperties instance by loading from ServiceLoader. Using class: {}",                             hp.getClass().getCanonicalName());            return hp;        }        hp = HystrixArchaiusHelper.createArchaiusDynamicProperties();        if (hp != null) {            logSupplier.getLogger().debug("Created HystrixDynamicProperties. Using class : {}",                     hp.getClass().getCanonicalName());            return hp;        }        hp = HystrixDynamicPropertiesSystemProperties.getInstance();        logSupplier.getLogger().info("Using System Properties for HystrixDynamicProperties! Using class: {}",                 hp.getClass().getCanonicalName());        return hp;    }

  HystrixConcurrencyStrategy

　　并发相关的策略类。

　　获取线程池，实际根据配置创建ThreadPoolExecutor。

/**     获取线程池*/    public ThreadPoolExecutor getThreadPool(final HystrixThreadPoolKey threadPoolKey, HystrixProperty
    
      corePoolSize, HystrixProperty
     
       maximumPoolSize, HystrixProperty
      
        keepAliveTime, TimeUnit unit, BlockingQueue
       
         workQueue) {        final ThreadFactory threadFactory = getThreadFactory(threadPoolKey);        final int dynamicCoreSize = corePoolSize.get();        final int dynamicMaximumSize = maximumPoolSize.get();        if (dynamicCoreSize > dynamicMaximumSize) {            logger.error("Hystrix ThreadPool configuration at startup for : " + threadPoolKey.name() + " is trying to set coreSize = " +                    dynamicCoreSize + " and maximumSize = " + dynamicMaximumSize + ".  Maximum size will be set to " +                    dynamicCoreSize + ", the coreSize value, since it must be equal to or greater than the coreSize value");            return new ThreadPoolExecutor(dynamicCoreSize, dynamicCoreSize, keepAliveTime.get(), unit, workQueue, threadFactory);        } else {            return new ThreadPoolExecutor(dynamicCoreSize, dynamicMaximumSize, keepAliveTime.get(), unit, workQueue, threadFactory);        }    }    public ThreadPoolExecutor getThreadPool(final HystrixThreadPoolKey threadPoolKey, HystrixThreadPoolProperties threadPoolProperties) {        final ThreadFactory threadFactory = getThreadFactory(threadPoolKey);        final boolean allowMaximumSizeToDivergeFromCoreSize = threadPoolProperties.getAllowMaximumSizeToDivergeFromCoreSize().get();        final int dynamicCoreSize = threadPoolProperties.coreSize().get();        final int keepAliveTime = threadPoolProperties.keepAliveTimeMinutes().get();        final int maxQueueSize = threadPoolProperties.maxQueueSize().get();        final BlockingQueue
        
          workQueue = getBlockingQueue(maxQueueSize);        if (allowMaximumSizeToDivergeFromCoreSize) {            final int dynamicMaximumSize = threadPoolProperties.maximumSize().get();            if (dynamicCoreSize > dynamicMaximumSize) {                logger.error("Hystrix ThreadPool configuration at startup for : " + threadPoolKey.name() + " is trying to set coreSize = " +                        dynamicCoreSize + " and maximumSize = " + dynamicMaximumSize + ".  Maximum size will be set to " +                        dynamicCoreSize + ", the coreSize value, since it must be equal to or greater than the coreSize value");                return new ThreadPoolExecutor(dynamicCoreSize, dynamicCoreSize, keepAliveTime, TimeUnit.MINUTES, workQueue, threadFactory);            } else {                return new ThreadPoolExecutor(dynamicCoreSize, dynamicMaximumSize, keepAliveTime, TimeUnit.MINUTES, workQueue, threadFactory);            }        } else {            return new ThreadPoolExecutor(dynamicCoreSize, dynamicCoreSize, keepAliveTime, TimeUnit.MINUTES, workQueue, threadFactory);        }    }    private static ThreadFactory getThreadFactory(final HystrixThreadPoolKey threadPoolKey) {        if (!PlatformSpecific.isAppEngineStandardEnvironment()) {            return new ThreadFactory() {                private final AtomicInteger threadNumber = new AtomicInteger(0);                @Override                public Thread newThread(Runnable r) {                    Thread thread = new Thread(r, "hystrix-" + threadPoolKey.name() + "-" + threadNumber.incrementAndGet());                    thread.setDaemon(true);                    return thread;                }            };        } else {            return PlatformSpecific.getAppEngineThreadFactory();        }    }    public BlockingQueue
         
           getBlockingQueue(int maxQueueSize) { if (maxQueueSize <= 0) { return new SynchronousQueue
          
           (); } else { return new LinkedBlockingQueue
           
            (maxQueueSize); } }
           
          
         
        
       
      
     
    

 　　在执行callable前提供用户对callable进行分装

public 
    
      Callable
     
       wrapCallable(Callable
      
        callable) {        return callable;    }
      
     
    

　　获取HystrixRequestVariable

public 
    
      HystrixRequestVariable
     
       getRequestVariable(final HystrixRequestVariableLifecycle
      
        rv) {        return new HystrixLifecycleForwardingRequestVariable
       
        (rv);    }
       
      
     
    

HystrixCommandExecutionHook

　　 hystrix命令执行过程中的回调接口，提供了一下回调接口。

/**    在命令执行前被调用*/    public 
    
      void onStart(HystrixInvokable
     
       commandInstance) {        //do nothing by default    }    /**     当接收到数据时被调用*/    public 
      
        T onEmit(HystrixInvokable
       
         commandInstance, T value) {        return value; //by default, just pass through    }    /**     *当命令异常时被调用     * @since 1.2     */    public 
        
          Exception onError(HystrixInvokable
         
           commandInstance, FailureType failureType, Exception e) { return e; //by default, just pass through } /** *当执行成功后被调用 * @since 1.4 */ public 
          
            void onSuccess(HystrixInvokable
           
             commandInstance) { //do nothing by default } /** 在线程池执行命令前执行*/ public 
            
              void onThreadStart(HystrixInvokable
             
               commandInstance) { //do nothing by default } /** 在线程池执行完成后调用*/ public 
              
                void onThreadComplete(HystrixInvokable
               
                 commandInstance) { // do nothing by default } /** 当开始执行命令时调用*/ public 
                
                  void onExecutionStart(HystrixInvokable
                 
                   commandInstance) { //do nothing by default } /** 当执行命令emits a value时调用 * * @param commandInstance The executing HystrixInvokable instance. * @param value value emitted * * @since 1.4 */ public 
                  
                    T onExecutionEmit(HystrixInvokable
                   
                     commandInstance, T value) { return value; //by default, just pass through } /** 执行抛出异常时调用*/ public 
                    
                      Exception onExecutionError(HystrixInvokable
                     
                       commandInstance, Exception e) { return e; //by default, just pass through } /** 当调用命令成功执行完调用 * @since 1.4 */ public 
                      
                        void onExecutionSuccess(HystrixInvokable
                       
                         commandInstance) { //do nothing by default } /** * Invoked when the fallback method in {@link HystrixInvokable} starts. * * @param commandInstance The executing HystrixInvokable instance. * * @since 1.2 */ public 
                        
                          void onFallbackStart(HystrixInvokable
                         
                           commandInstance) { //do nothing by default } /** * Invoked when the fallback method in {@link HystrixInvokable} emits a value. * * @param commandInstance The executing HystrixInvokable instance. * @param value value emitted * * @since 1.4 */ public 
                          
                            T onFallbackEmit(HystrixInvokable
                           
                             commandInstance, T value) { return value; //by default, just pass through } /** * Invoked when the fallback method in {@link HystrixInvokable} fails with an Exception. * * @param commandInstance The executing HystrixInvokable instance. * @param e exception object * * @since 1.2 */ public 
                            
                              Exception onFallbackError(HystrixInvokable
                             
                               commandInstance, Exception e) { //by default, just pass through return e; } /** * Invoked when the user-defined execution method in {@link HystrixInvokable} completes successfully. * * @param commandInstance The executing HystrixInvokable instance. * * @since 1.4 */ public 
                              
                                void onFallbackSuccess(HystrixInvokable
                               
                                 commandInstance) { //do nothing by default } /** 如果从缓存中获取数据时调用*/ public 
                                
                                  void onCacheHit(HystrixInvokable
                                 
                                   commandInstance) { //do nothing by default } /** 当取消挂载时被调用 * @since 1.5.9 */ public 
                                  
                                    void onUnsubscribe(HystrixInvokable
                                   
                                     commandInstance) { //do nothing by default }
                                   
                                  
                                 
                                
                               
                              
                             
                            
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     
    

 HystrixEventNotifier

　　hystrix命令执行过程中，接收相应的事件通知。

/**    接收到消息后执行　　接受一下消息：   RESPONSE_FROM_CACHE如果该command从缓存中获取数据   CANCELLED 如果command在完成前unsubscrible   EXCEPTION_THROWN 如果command出现异常   EMIT 如果command发送数据   THREAD_POOL_REJECTED 如果线程池抛出reject异常   FAILURE 执行失败异常　　FALLBACK_EMIT执行fallback返回数据　　FALLBACK_SUCCESS执行fallback成功　　FALLBACK_FAILURE执行fallback发生异常　　FALLBACK_REJECTION超过信号量，fallback未被执行。　　FALLBACK_MISSING　　SEMAPHORE_REJECTED信号量模型执行被拒绝。　　SHORT_CIRCUITED熔断*/    public void markEvent(HystrixEventType eventType, HystrixCommandKey key) {        // do nothing    }    /**     * Called after a command is executed using thread isolation.     * Will not get called if a command is rejected, short-circuited etc.*/    public void markCommandExecution(HystrixCommandKey key, ExecutionIsolationStrategy isolationStrategy, int duration, List
    
      eventsDuringExecution) {        // do nothing    }
    

 HystrixMetricsPublisher

　　HystrixMetricsPublisherFactory使用该插件来创建HystrixMetricsPublisherCommand、HystrixMetricsPublisherThreadPool、HystrixMetricsPublisherCollapser，并调用相应的initialize方法，这些类用来向第三方publish hystrix的metrics信息。

private final ConcurrentHashMap
    
      threadPoolPublishers = new ConcurrentHashMap
     
      ();    /* package */ HystrixMetricsPublisherThreadPool getPublisherForThreadPool(HystrixThreadPoolKey threadPoolKey, HystrixThreadPoolMetrics metrics, HystrixThreadPoolProperties properties) {        // attempt to retrieve from cache first        HystrixMetricsPublisherThreadPool publisher = threadPoolPublishers.get(threadPoolKey.name());        if (publisher != null) {            return publisher;        }        // it doesn't exist so we need to create it        publisher = HystrixPlugins.getInstance().getMetricsPublisher().getMetricsPublisherForThreadPool(threadPoolKey, metrics, properties);        // attempt to store it (race other threads)        HystrixMetricsPublisherThreadPool existing = threadPoolPublishers.putIfAbsent(threadPoolKey.name(), publisher);        if (existing == null) {            // we won the thread-race to store the instance we created so initialize it            publisher.initialize();            // done registering, return instance that got cached            return publisher;        } else {            // we lost so return 'existing' and let the one we created be garbage collected            // without calling initialize() on it            return existing;        }    }
     
    

　　

 HystrixPropertiesStrategy

　　创建HystrixCommandProperties、HystrixThreadPoolProperties、HystrixCollapserProperties、HystrixTimerThreadPoolProperties

/**     创建HystrixCommandProperties*/    public HystrixCommandProperties getCommandProperties(HystrixCommandKey commandKey, HystrixCommandProperties.Setter builder) {        return new HystrixPropertiesCommandDefault(commandKey, builder);    }/**     创建HystrixThreadPoolProperties*/    public HystrixThreadPoolProperties getThreadPoolProperties(HystrixThreadPoolKey threadPoolKey, HystrixThreadPoolProperties.Setter builder) {        return new HystrixPropertiesThreadPoolDefault(threadPoolKey, builder);    }/**     创建HystrixCollapserProperties*/    public HystrixCollapserProperties getCollapserProperties(HystrixCollapserKey collapserKey, HystrixCollapserProperties.Setter builder) {        return new HystrixPropertiesCollapserDefault(collapserKey, builder);    }/**     创建HystrixTimerThreadPoolProperties*/    public HystrixTimerThreadPoolProperties getTimerThreadPoolProperties() {        return new HystrixPropertiesTimerThreadPoolDefault();    }

 

http://www.cnblogs.com/zhangwanhua/p/7878515.html