spring cloud源码分析-zuul路由的部分源码解析

版本：
spring-boot:1.5.3.RELEASE；
spring cloud:Dalston.RELEASE(1.3.0.RELEASE)

路由定位器

• 配置所在jar包：spring-cloud-netflix-core-1.3.0.RELEASE.jar
• 顶层接口：RouteLocator
• 可刷新的路由：RefreshableRouteLocator extends RouteLocator
• 路由处理器：CompositeRouteLocator implements RefreshableRouteLocator，所有的路由定位器都交由给它处理
• 默认加载的路由定位器：SimpleRouteLocator implements RouteLocator, Ordered，实现Ordered接口达到排序的效果
• 配置类：ZuulProxyConfiguration extends ZuulConfiguration，ZuulConfiguration中包含默认的一些公共的filter，ZuulProxyConfiguration包含spring cloud的需要的一些filter，如：host解析、ribbon负载均衡等
• zuul初始化配置不是通过spring.factories配置文件，而是通过@EnableZuulProxy注解引入配置的，源码如下：

@EnableCircuitBreaker
@EnableDiscoveryClient
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(ZuulProxyConfiguration.class)
public @interface EnableZuulProxy {
}

• zuul路由的请求是通过filter发出去的
• 可刷新的路由定位器（RefreshableRouteLocator）是基于监听spring容器事件实现的，并且都是在配置类中（内部静态类），有两个地方：
  

  ZuulConfiguration中的监听：

//加载bean
@Bean
public ApplicationListener<ApplicationEvent> zuulRefreshRoutesListener() {
    return new ZuulRefreshListener();
}

//内部静态类
private static class ZuulRefreshListener implements ApplicationListener<ApplicationEvent> {

    @Autowired
    private ZuulHandlerMapping zuulHandlerMapping;
    
    private HeartbeatMonitor heartbeatMonitor = new HeartbeatMonitor();
    
    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof ContextRefreshedEvent
                || event instanceof RefreshScopeRefreshedEvent
                || event instanceof RoutesRefreshedEvent) {
            this.zuulHandlerMapping.setDirty(true);
        }
        else if (event instanceof HeartbeatEvent) {
            if (this.heartbeatMonitor.update(((HeartbeatEvent) event).getValue())) {
                this.zuulHandlerMapping.setDirty(true);
            }
        }
    }
    
}

ZuulProxyConfiguration中的监听：

//加载bean
@Bean
public ApplicationListener<ApplicationEvent> zuulDiscoveryRefreshRoutesListener() {
    return new ZuulDiscoveryRefreshListener();
}

//内部静态类
private static class ZuulDiscoveryRefreshListener implements ApplicationListener<ApplicationEvent> {

    private HeartbeatMonitor monitor = new HeartbeatMonitor();
    
    @Autowired
    private ZuulHandlerMapping zuulHandlerMapping;
    
    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof InstanceRegisteredEvent) {
            reset();
        }
        else if (event instanceof ParentHeartbeatEvent) {
            ParentHeartbeatEvent e = (ParentHeartbeatEvent) event;
            resetIfNeeded(e.getValue());
        }
        else if (event instanceof HeartbeatEvent) {
            HeartbeatEvent e = (HeartbeatEvent) event;
            resetIfNeeded(e.getValue());
        }
    
    }
    
    private void resetIfNeeded(Object value) {
        if (this.monitor.update(value)) {
            reset();
        }
    }
    
    private void reset() {
        this.zuulHandlerMapping.setDirty(true);
    }
}

以上可以看出有个问题，两个地方都监听了HeartbeatEvent，并且做了相同的处理，会导致重复刷新

• 触发心跳事件：SimpleApplicationEventMulticaster-->167行
• 心跳是个线程池专门处理，初始化是在：com.netflix.discovery.DiscoveryClient-->1247行
• 心跳的间隔时间配置有bug（配置没生效，配置的名称是间隔，但是线程池调度的时候传给超时时间的），默认是30分钟，配置是：

#org.springframework.cloud.netflix.eureka.EurekaInstanceConfigBean.leaseRenewalIntervalInSeconds
eureka.instance.leaseRenewalIntervalInSeconds=30