【Eureka】【源码+图解】【七】Eureka的下线功能

【Eureka】【源码+图解】【六】Eureka的续约功能

6. 下线

主动下线方式

服务端：/eureka/apps/{application.name}/{instance-id}，以本系列文章的helloworld为例，发送DELETE请求http://localhost:3333/eureka/apps/MY-EUREKA-CLIENT/localhost:my-eureka-client:2222便可将客户端实例下线

客户端：

1、创建Controller

@RestController
public class EurekaController {

    @GetMapping("/cancel")
    public void cancel() {
        DiscoveryManager.getInstance().shutdownComponent();
    }
}

2、浏览器直接拍http://localhost:2222/cancel即可将客户端实例下线

下线的整体流程图

主要分析绿色的三个步骤

6.1 shutdown()

public class DiscoveryClient implements EurekaClient {
	@PreDestroy
    @Override
    public synchronized void shutdown() {
        if (isShutdown.compareAndSet(false, true)) {
            ......
                // 注销监听器
            if (statusChangeListener != null && applicationInfoManager != null) {
                applicationInfoManager.unregisterStatusChangeListener(statusChangeListener.getId());
            }
            // 取消定时任务，包括注册、续约、更新注册信息等
            cancelScheduledTasks();
            // 注销
            if (applicationInfoManager != null
                    && clientConfig.shouldRegisterWithEureka()
                    && clientConfig.shouldUnregisterOnShutdown()) {
                applicationInfoManager.setInstanceStatus(InstanceStatus.DOWN);
                unregister(); // 向服务端发送下线请求
            }
            if (eurekaTransport != null) {
                // 关闭eurekaTransport
                eurekaTransport.shutdown();
            }
            ......
        }
    }
}

6.2 服务端cancel

public abstract class AbstractInstanceRegistry implements InstanceRegistry {
	@Override
    public boolean cancel(String appName, String id, boolean isReplication) {
        // 1、从内存实例注册表registry删除
        // 2、添加到recentCanceledQueue
        // 3、从overriddenInstanceStatusMap删除
        // 4、添加到recentlyChangedQueue
        // 5、从缓存responseCache中删除
        return internalCancel(appName, id, isReplication);
    }
}

6.3 同步其他server节点

public class PeerAwareInstanceRegistryImpl extends AbstractInstanceRegistry implements PeerAwareInstanceRegistry {
	@Override
    public boolean cancel(final String appName, final String id,
                          final boolean isReplication) {
        if (super.cancel(appName, id, isReplication)) {
            // 除了Action.Cancel与register不同，其他可参考register章节
            replicateToPeers(Action.Cancel, appName, id, null, null, isReplication);
            return true;
        }
        return false;
    }
}

未完待续