第四篇：Spring Cloud Eureka服务上下线监控

在一些场景下，我们需要监听eureka服务中心的一些状态，譬如某个微服务挂掉了，我们希望能监听到，并给管理员发送邮件通知。

在Eureka服务中进行检测通知，Eureka中提供了事件监听的方式来支持扩展。

• EurekaInstanceCanceledEvent 服务下线事件
• EurekaInstanceRegisteredEvent 服务注册事件
• EurekaInstanceRenewedEvent 服务续约事件
• EurekaRegistryAvailableEvent Eureka注册中心启动事件
• EurekaServerStartedEvent Eureka Server启动事件

import com.netflix.discovery.shared.Applications;
import com.netflix.eureka.EurekaServerContextHolder;
import com.netflix.eureka.registry.PeerAwareInstanceRegistry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.netflix.eureka.server.event.EurekaInstanceCanceledEvent;
import org.springframework.cloud.netflix.eureka.server.event.EurekaInstanceRegisteredEvent;
import org.springframework.cloud.netflix.eureka.server.event.EurekaInstanceRenewedEvent;
import org.springframework.cloud.netflix.eureka.server.event.EurekaRegistryAvailableEvent;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableScheduling;

/**
 * eureka事件监听
 * 例如：用于监听eureka服务停机通知
 *
 * @author hrabbit
 * @date 2018-09-13
 */
@Configuration
@EnableScheduling
public class EurekaInstanceCanceledListener implements ApplicationListener {
    private Logger log = LoggerFactory.getLogger(EurekaInstanceCanceledListener.class);

    @Override
    public void onApplicationEvent(ApplicationEvent applicationEvent) {
        // EurekaInstanceCanceledEvent 服务下线事件
        if (applicationEvent instanceof EurekaInstanceCanceledEvent) {
            EurekaInstanceCanceledEvent event = (EurekaInstanceCanceledEvent) applicationEvent;
            // 获取当前Eureka实例中的节点信息
            PeerAwareInstanceRegistry registry = EurekaServerContextHolder.getInstance().getServerContext().getRegistry();
            Applications applications = registry.getApplications();
            // 遍历获取已注册节点中与当前失效节点ID一致的节点信息
            applications.getRegisteredApplications().forEach((registeredApplication) -> {
                registeredApplication.getInstances().forEach((instance) -> {
                    if (instance.getInstanceId().equals(event.getServerId())) {
                        log.info("服务：" + instance.getAppName() + " 挂啦。。。");
                        // TODO: 2018-09-13 扩展消息提醒 邮件、手机短信、微信等
                    }
                });
            });
        }
        //EurekaInstanceRegisteredEvent 服务注册事件
        if (applicationEvent instanceof EurekaInstanceRegisteredEvent) {
            EurekaInstanceRegisteredEvent event = (EurekaInstanceRegisteredEvent) applicationEvent;
            log.info("服务：" + event.getInstanceInfo().getAppName() + " 注册成功啦...");
        }
        //EurekaInstanceRenewedEvent 服务续约事件
        if (applicationEvent instanceof EurekaInstanceRenewedEvent) {
            EurekaInstanceRenewedEvent event = (EurekaInstanceRenewedEvent) applicationEvent;
            log.info("服务：" + event.getInstanceInfo().getAppName() + "续约...");
        }
        //EurekaRegistryAvailableEvent Eureka注册中心启动事件
        if (applicationEvent instanceof EurekaRegistryAvailableEvent) {
            log.info("Eureka注册中心启动了...");
        }

    }
}

这样我们可以构建自己的注册中心监控，当然这种写法是为了方便大家了解几个实践，下面的写法显得更加简洁和符合规范。

import com.netflix.appinfo.InstanceInfo;
import org.springframework.cloud.netflix.eureka.server.event.*;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

/**
 * eureka事件监听
 * 例如：用于监听eureka服务停机通知
 *
 * @author hrabbit
 * @date 2018-09-13
 */
@Component
public class EurekaStateChangeListener {
    /**
     * EurekaInstanceCanceledEvent 服务下线事件
     * @param event
     */
    @EventListener
    public void listen(EurekaInstanceCanceledEvent event) {
        System.out.println(event.getServerId() + "\t" + event.getAppName() + " 服务下线");
    }

    /**
     * EurekaInstanceRegisteredEvent 服务注册事件
     * @param event
     */
    @EventListener
    public void listen(EurekaInstanceRegisteredEvent event) {
        InstanceInfo instanceInfo = event.getInstanceInfo();
        System.out.println(instanceInfo.getAppName() + "进行注册");
    }

    /**
     * EurekaInstanceRenewedEvent 服务续约事件
     * @param event
     */
    @EventListener
    public void listen(EurekaInstanceRenewedEvent event) {
        System.out.println(event.getServerId() + "\t" + event.getAppName() + " 服务进行续约");
    }

    /**
     * EurekaRegistryAvailableEvent Eureka注册中心启动事件
     * @param event
     */
    @EventListener
    public void listen(EurekaRegistryAvailableEvent event) {
        System.out.println("注册中心 启动");
    }

    /**
     * EurekaServerStartedEvent Eureka Server启动事件
     * @param event
     */
    @EventListener
    public void listen(EurekaServerStartedEvent event) {
        System.out.println("Eureka Server 启动");
    }
}