spring cloud gateway 限流配置 动态加载(spring cloud gateway 负载均衡)

        我使用的是nacos配置中心。其实这里的动态路由大部分就是nacos的原理了。

NacosConfigAutoConfiguration中初始化了一个bean，nacosContextRefresher。

public class NacosContextRefresher
		implements ApplicationListener, ApplicationContextAware {

它 本身监听readyEvent，当启动完成后

@Override
	public void onApplicationEvent(ApplicationReadyEvent event) {
		// many Spring context
		if (this.ready.compareAndSet(false, true)) {
			this.registerNacosListenersForApplications();
		}
	}

进行注册nacos的监听器，我们直接跟踪到最底层方法：

private void registerNacosListener(final String groupKey, final String dataKey) {
        //group和dataid 组成新的key
		String key = NacosPropertySourceRepository.getMapKey(dataKey, groupKey);

        //listener监听器map 注册监听器
		Listener listener = listenerMap.computeIfAbsent(key,
				lst -> new AbstractSharedListener() {
					@Override
					public void innerReceive(String dataId, String group,
							String configInfo) {
                        //原子计数器,后面nacos专题讲做什么的
						refreshCountIncrement();
                        //新增刷新记录
						nacosRefreshHistory.addRefreshRecord(dataId, group, configInfo);
						// 发布 RefreshEvent，这个是spring cloud context 公共的事件，不止            
                        //nacos
						applicationContext.publishEvent(
								new RefreshEvent(this, null, "Refresh Nacos config"));
						if (log.isDebugEnabled()) {
							log.debug(String.format(
									"Refresh Nacos config group=%s,dataId=%s,configInfo=%s",
									group, dataId, configInfo));
						}
					}
				});
		try {
            //listner和key 进行绑定，这样就能哪个配置文件刷新时，执行哪个listener
			configService.addListener(dataKey, groupKey, listener);
		}
		catch (NacosException e) {
			log.warn(String.format(
					"register fail for nacos listener ,dataId=[%s],group=[%s]", dataKey,
					groupKey), e);
		}
	}

当我们点击nacos配置中心的  配置文件发布按钮后，就会执行到上图里的监听器里。会发布一个spring cloud context的refreshEvent，org.springframework.cloud.endpoint.event.RefreshEventListener会监听到事件并最终又会调用org.springframework.cloud.context.scope.refresh.RefreshScope#refreshAll方法

@ManagedOperation(description = "Dispose of the current instance of all beans "
			+ "in this scope and force a refresh on next method execution.")
	public void refreshAll() {
		super.destroy();
		this.context.publishEvent(new RefreshScopeRefreshedEvent());
	}

这里看到又发布了一个RefreshScopeRefreshedEvent事件。而之前我们看过RouteRefreshListener的，我们看看它监听哪些事件怎么处理的

@Override
	public void onApplicationEvent(ApplicationEvent event) {
		if (event instanceof ContextRefreshedEvent) {
			ContextRefreshedEvent refreshedEvent = (ContextRefreshedEvent) event;
			if (!WebServerApplicationContext.hasServerNamespace(refreshedEvent.getApplicationContext(), "management")) {
				reset();
			}
		}
		else if (event instanceof RefreshScopeRefreshedEvent || 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());
		}
	}

我们看到它监听了所有的事件，但是它内部有区分事件处理，正好也有 RefreshScopeRefreshedEvent事件，因此 会重新触发重加载route的请求。至于properties为什么会改变，看nacos时再说