Spring Cloud : Eureka Client registration/deregistration cycle

Question

为了熟悉 Spring Cloud 的 Eureka 客户端/服务器机制，我尝试将客户端连接到 Eureka 服务器并每 5 分钟切换一次连接打开/关闭，以查看 Eureka 服务器如何处理此问题。

我有两个 Eureka 客户端。

首先是使用此代码向我提供有关已注册应用程序的信息:

@Autowired
private DiscoveryClient discoveryClient;

@RequestMapping(value = "/services", produces = MediaType.APPLICATION_JSON)
public ResponseEntity<ResourceSupport> applications() {
    ResourceSupport resource = new ResourceSupport();

    Set<String> regions = discoveryClient.getAllKnownRegions();

    for (String region : regions) {
        Applications allApps = discoveryClient.getApplicationsForARegion(region);
        List<Application> registeredApps = allApps.getRegisteredApplications();
        Iterator<Application> it = registeredApps.iterator();

        while (it.hasNext()) {
            Application app = it.next();

             List<InstanceInfo> instancesInfos = app.getInstances();

             if (instancesInfos != null && !instancesInfos.isEmpty()) {
                 //only show one of the instances
                 InstanceInfo info = instancesInfos.get(0);
                 resource.add(new Link(info.getHomePageUrl(), "urls"));
             }
        }
    }

    return new ResponseEntity<ResourceSupport>(resource, HttpStatus.OK);
}

第二个 Eureka 客户端每 5 分钟注册/注销一次:

private static final long EUREKA_INTERVAL = 5 * 60000;

public static void main(String[] args) {
    ConfigurableApplicationContext context = SpringApplication.run(MyServiceApplication.class);

    long currentTime = System.currentTimeMillis();
    long lastToggleTime = System.currentTimeMillis();
    boolean connected = true;
    while (true) {
        if (currentTime - lastToggleTime > EUREKA_INTERVAL) {
            if (connected) {
                System.err.println("disconnect");
                DiscoveryManager.getInstance().shutdownComponent();
                connected = false;
                lastToggleTime = System.currentTimeMillis();
            }
            else {
                System.err.println("connect");
                DiscoveryManager.getInstance().initComponent(
                        DiscoveryManager.getInstance().getEurekaInstanceConfig(),
                        DiscoveryManager.getInstance().getEurekaClientConfig());
                connected = true;
                lastToggleTime = System.currentTimeMillis();
            }
        }
        currentTime = System.currentTimeMillis();
    }

}

第二个Eureka客户端的日志输出如下:

disconnect
2015-03-26 13:59:23.713  INFO 3452 --- [           main] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_MYAPPNAME/MYMEGAHOSTNAME - deregister  status: 200
connect
2015-03-26 14:04:23.870  INFO 3452 --- [           main] com.netflix.discovery.DiscoveryClient    : Disable delta property : false
2015-03-26 14:04:23.870  INFO 3452 --- [           main] com.netflix.discovery.DiscoveryClient    : Single vip registry refresh property : null
2015-03-26 14:04:23.870  INFO 3452 --- [           main] com.netflix.discovery.DiscoveryClient    : Force full registry fetch : false
2015-03-26 14:04:23.870  INFO 3452 --- [           main] com.netflix.discovery.DiscoveryClient    : Application is null : false
2015-03-26 14:04:23.870  INFO 3452 --- [           main] com.netflix.discovery.DiscoveryClient    : Registered Applications size is zero : true
2015-03-26 14:04:23.870  INFO 3452 --- [           main] com.netflix.discovery.DiscoveryClient    : Application version is -1: true
2015-03-26 14:04:23.889  INFO 3452 --- [           main] com.netflix.discovery.DiscoveryClient    : Getting all instance registry info from the eureka server
2015-03-26 14:04:23.892  INFO 3452 --- [           main] com.netflix.discovery.DiscoveryClient    : The response status is 200
2015-03-26 14:04:23.894  INFO 3452 --- [           main] com.netflix.discovery.DiscoveryClient    : Starting heartbeat executor: renew interval is: 30
2015-03-26 14:04:53.916  INFO 3452 --- [ool-11-thread-1] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_MYAPPNAME/MYMEGAHOSTNAME - Re-registering apps/MYAPPNAME
2015-03-26 14:04:53.916  INFO 3452 --- [ool-11-thread-1] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_MYAPPNAME/MYMEGAHOSTNAME: registering service...
2015-03-26 14:04:53.946  INFO 3452 --- [ool-11-thread-1] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_MYAPPNAME/MYMEGAHOSTNAME - registration status: 204

第一次启动两个 Eureka 客户端时，这很有效。第二个客户端由第一个客户端显示，第二个客户端在 Eureka 服务器控制台中可见。当第二个客户端与 Eureka 服务器断开连接时，它不再列在那里，第一个客户端也不再显示它。

不幸的是，当第二个客户端重新连接到 Eureka 服务器时，Eureka 服务器控制台只显示一个大红色突出显示“DOWN (1)”，而第一个客户端不再显示第二个客户端。我在这里缺少什么？

---

解决方案:

基于 Dave Sayer 的 answer我的解决方案是添加一个自定义的 @Configuration ，它具有 Autowiring 的 EurekaDiscoveryClientConfiguration 并启动一个线程来切换注册。请注意，这仅用于测试目的，因此它可能是一个非常难看的解决方案 ;-)

@Configuration
static public class MyDiscoveryClientConfigServiceAutoConfiguration {

    @Autowired
    private EurekaDiscoveryClientConfiguration lifecycle;

    @PostConstruct
    public void init() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                long currentTime = System.currentTimeMillis();
                long lastToggleTime = System.currentTimeMillis();
                boolean connected = true;

                while (true) {
                    if (currentTime - lastToggleTime > EUREKA_INTERVAL) {
                        if (connected) {
                            System.err.println("disconnect");

                            lifecycle.stop();
                            DiscoveryManager.getInstance().getDiscoveryClient().shutdown();
                            connected = false;
                            lastToggleTime = System.currentTimeMillis();
                        }
                        else {
                            System.err.println("connect");
                            DiscoveryManager.getInstance().initComponent(
                                    DiscoveryManager.getInstance().getEurekaInstanceConfig(),
                                    DiscoveryManager.getInstance().getEurekaClientConfig());

                            lifecycle.start();
                            connected = true;
                            lastToggleTime = System.currentTimeMillis();
                        }
                    }
                    currentTime = System.currentTimeMillis();
                }
            }
        }).start();
    }

}

Answer 1

您对 DiscoveryManager.getInstance().initComponent() 的调用未设置状态(默认为 DOWN)。在 Spring Cloud 中，我们在特殊的 EurekaDiscoveryClientConfiguration.start() 生命周期中处理它。您可以像这样注入(inject)并重新使用它:

@Autowired
private EurekaDiscoveryClientConfiguration lifecycle;

@PostConstruct
public void init() {
    this.lifecycle.stop();
    if (DiscoveryManager.getInstance().getDiscoveryClient() != null) {
        DiscoveryManager.getInstance().getDiscoveryClient().shutdown();
    }
    ApplicationInfoManager.getInstance().initComponent(this.instanceConfig);
    DiscoveryManager.getInstance().initComponent(this.instanceConfig,
            this.clientConfig);
    this.lifecycle.start();
}

(代码取自此处:https://github.com/spring-cloud/spring-cloud-netflix/blob/master/spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/config/DiscoveryClientConfigServiceAutoConfiguration.java#L58)。