服务容错保护(Spring Cloud Hystrix)之断路器原理

源码：

//
//学习资料《springcloud 微服务实战》《springcloud微服务全栈技术与案例解析》
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//package com.netflix.hystrix;import com.netflix.hystrix.HystrixCommandGroupKey;
import com.netflix.hystrix.HystrixCommandKey;
import com.netflix.hystrix.HystrixCommandMetrics;
import com.netflix.hystrix.HystrixCommandProperties;
import com.netflix.hystrix.HystrixCommandMetrics.HealthCounts;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;public interface HystrixCircuitBreaker {boolean allowRequest();//每个请求判断是都要执行boolean isOpen();//判断断路器是都打开void markSuccess();//关闭断路器    //定义一个什么都不做的断路器实现，public static class NoOpCircuitBreaker implements HystrixCircuitBreaker {public NoOpCircuitBreaker() {}public boolean allowRequest() {return true;}public boolean isOpen() {return false;}public void markSuccess() {}}public static class HystrixCircuitBreakerImpl implements HystrixCircuitBreaker {private final HystrixCommandProperties properties;//实例的属性对象private final HystrixCommandMetrics metrics;//记录各类度量指标对象private AtomicBoolean circuitOpen = new AtomicBoolean(false);//断路器是都打开标志，默认falseprivate AtomicLong circuitOpenedOrLastTestedTime = new AtomicLong();//上一次的时间戳protected HystrixCircuitBreakerImpl(HystrixCommandKey key, HystrixCommandGroupKey commandGroup, HystrixCommandProperties properties, HystrixCommandMetrics metrics) {this.properties = properties;this.metrics = metrics;}//用于在半开路状态下，如果成功就将断路器关闭，并重置指标对象public void markSuccess() {if(this.circuitOpen.get() && this.circuitOpen.compareAndSet(true, false)) {this.metrics.resetStream();}}public boolean allowRequest() {  //先根据配置文件有没有配置，默认情况根据if(((Boolean)this.properties.circuitBreakerForceOpen().get()).booleanValue()) {return false;} else if(((Boolean)this.properties.circuitBreakerForceClosed().get()).booleanValue()) {this.isOpen();return true;} else {//默认情况下判断return !this.isOpen() || this.allowSingleTest();}}public boolean allowSingleTest() {long timeCircuitOpenedOrWasLastTested = this.circuitOpenedOrLastTestedTime.get();return this.circuitOpen.get() && System.currentTimeMillis() > timeCircuitOpenedOrWasLastTested + (long)((Integer)this.properties.circuitBreakerSleepWindowInMilliseconds().get()).intValue() && this.circuitOpenedOrLastTestedTime.compareAndSet(timeCircuitOpenedOrWasLastTested, System.currentTimeMillis());}public boolean isOpen() {if(this.circuitOpen.get()) {return true;     //如果开启就直接返回ture} else {    //否则根据health一些健康指标进行判断是否开启HealthCounts health = this.metrics.getHealthCounts();if(health.getTotalRequests() < (long)((Integer)this.properties.circuitBreakerRequestVolumeThreshold().get()).intValue()) {return false;} else if(health.getErrorPercentage() < ((Integer)this.properties.circuitBreakerErrorThresholdPercentage().get()).intValue()) {return false;} else if(this.circuitOpen.compareAndSet(false, true)) {this.circuitOpenedOrLastTestedTime.set(System.currentTimeMillis());return true;} else {return true;}}}}public static class Factory {   //静态工厂记录保存Hystrix与key的对应关系保存在map中private static ConcurrentHashMap circuitBreakersByCommand = new ConcurrentHashMap();public Factory() {}public static HystrixCircuitBreaker getInstance(HystrixCommandKey key, HystrixCommandGroupKey group, HystrixCommandProperties properties, HystrixCommandMetrics metrics) {HystrixCircuitBreaker previouslyCached = (HystrixCircuitBreaker)circuitBreakersByCommand.get(key.name());if(previouslyCached != null) {return previouslyCached;} else {HystrixCircuitBreaker cbForCommand = (HystrixCircuitBreaker)circuitBreakersByCommand.putIfAbsent(key.name(), new HystrixCircuitBreaker.HystrixCircuitBreakerImpl(key, group, properties, metrics));return cbForCommand == null?(HystrixCircuitBreaker)circuitBreakersByCommand.get(key.name()):cbForCommand;}}public static HystrixCircuitBreaker getInstance(HystrixCommandKey key) {return (HystrixCircuitBreaker)circuitBreakersByCommand.get(key.name());}static void reset() {circuitBreakersByCommand.clear();}}
}

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