1、为什么要服务注销
当服务升级上线时，为了平滑过渡，一般会先把老的服务从注册中心上摘除（服务本身不停止），等该服务完全没有流量时，再进行下线的操作。采用SpringCloudConsul时，内部默认每3s和注册中心同步一次心跳，并以此刷新各个服务的ip列表。当某个服务从注册中心注销时，不需要进行广播，由心跳机制保证该注册中心剩余的所有服务能够感知到。
2、SpringCloudConsul提供的方法
SpringCloudConsul提供了一个ConsulAutoServiceRegistration类，该类主要提供服务的注册和注销功能，源码如下：
/*
* Copyright 2013-2016 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.cloud.consul.serviceregistry;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.boot.web.context.WebServerInitializedEvent;
import org.springframework.cloud.client.serviceregistry.AbstractAutoServiceRegistration;
import org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationProperties;
import org.springframework.cloud.consul.discovery.ConsulDiscoveryProperties;
import org.springframework.retry.annotation.Retryable;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
/**
* @author Spencer Gibb
*/
public class ConsulAutoServiceRegistration extends AbstractAutoServiceRegistration<ConsulRegistration> {
private static Log log = LogFactory.getLog(ConsulAutoServiceRegistration.class);
private ConsulDiscoveryProperties properties;
private ConsulAutoRegistration registration;
public ConsulAutoServiceRegistration(ConsulServiceRegistry serviceRegistry,
AutoServiceRegistrationProperties autoServiceRegistrationProperties,
ConsulDiscoveryProperties properties, ConsulAutoRegistration registration) {
super(serviceRegistry, autoServiceRegistrationProperties);
this.properties = properties;
this.registration = registration;
}
void setPortIfNeeded(int port) {
getPort().compareAndSet(0, port);
}
@Override
protected ConsulAutoRegistration getRegistration() {
if (this.registration.getService().getPort() == null && this.getPort().get() > 0) {
this.registration.initializePort(this.getPort().get());
}
Assert.notNull(this.registration.getService().getPort(), "service.port has not been set");
return this.registration;
}
@Override
protected ConsulAutoRegistration getManagementRegistration() {
return this.registration.managementRegistration();
}
@Override
@Retryable(interceptor = "consulRetryInterceptor")
public void start() {
super.start();
}
@Override
protected void register() {
if (!this.properties.isRegister()) {
log.debug("Registration disabled.");
return;
}
super.register();
}
@Override
protected void registerManagement() {
if (!this.properties.isRegister()) {
return;
}
super.registerManagement();
}
@Override
protected Object getConfiguration() {
return properties;
}
@Override
protected void deregister() {
if (!this.properties.isRegister() || !this.properties.isDeregister()) {
return;
}
super.deregister();
}
@Override
protected void deregisterManagement() {
if (!this.properties.isRegister() || !this.properties.isDeregister()) {
return;
}
super.deregisterManagement();
}
@Override
protected boolean isEnabled() {
return this.properties.getLifecycle().isEnabled();
}
@Override
@SuppressWarnings("deprecation")
protected String getAppName() {
String appName = properties.getServiceName();
return StringUtils.isEmpty(appName) ? super.getAppName() : appName;
}
@Override
public void bind(WebServerInitializedEvent event) {
// do nothing so we can listen for this event in a different class
// this ensures start() can be retried if spring-retry is available
}
}
其中服务注销的方法逻辑是：
image-20190218160430479
该方法会最终是调用consul提供的restfulAPI去进行服务的注销：
image-20190218160611472
3、测试SpringCloudConsul的注销方法
我们写一段代码进行服务注销的测试：
@RestController
public class ConsulController {
private final ConsulAutoServiceRegistration serviceRegistration;
public ConsulController(ConsulAutoServiceRegistration serviceRegistration) {
this.serviceRegistration = serviceRegistration;
}
@DeleteMapping("deregister")
public void deregister() {
serviceRegistration.stop();
}
}
服务启动后consul界面显示服务状态为绿色，代表正常：
image-20190218160840196
执行该接口后，正常情况下consul会摘除这个服务的注册信息，但是多试验几次后，会发现服务信息还在，这个时候如果服务停止的话，必然会出现调用异常的情况，consul上的服务状态为橙色:
image-20190218161830400
image-20190218162026267
4、完整的注销操作
显然以上的做法并不能真正的完成服务注销的操作，consul的注销操作需要到集群中的节点上才能完成，具体代码如下：
@RestController
@Slf4j
public class ConsulController {
private final ConsulClient consulClient;
private final ConsulRegistration consulRegistration;
public ConsulController(ConsulClient consulClient, ConsulRegistration consulRegistration) {
this.consulClient = consulClient;
this.consulRegistration = consulRegistration;
}
@DeleteMapping("api/deregister")
public void deregister() {
String currentInstanceId = consulRegistration.getInstanceId();
List<Member> members = consulClient.getAgentMembers().getValue();
for (Member member : members) {
String address = member.getAddress();
ConsulClient clearClient = new ConsulClient(address);
try {
Map<String, Service> serviceMap = clearClient.getAgentServices().getValue();
for (Entry<String, Service> entry : serviceMap.entrySet()) {
Service service = entry.getValue();
String instanceId = service.getId();
if (currentInstanceId.equals(instanceId)) {
log.warn("在{}客户端上的服务 :{}为无效服务，准备清理...................", address, currentInstanceId);
clearClient.agentServiceDeregister(currentInstanceId);
}
}
} catch (Exception e) {
log.error("异常信息: {}", e);
}
}
}
}
5、如何让服务在consul上进入维护模式（临时摘除）
-
暴露
/service-registry端点（需要引入spring-boot-starter-actuator支持） -
SpringCloudConsul提供【上线】和【离线】两种服务状态的设置，具体代码在ConsulServiceRegistry类中
image-20190218164331970
-
发送POST请求到
/actuator/service-registry端点，此时状态应为OUT_OF_SERVICEcurl -X "POST" "http://localhost:8081/actuator/service-registry?status=OUT_OF_SERVICE" -H "Content-Type: application/vnd.spring-boot.actuator.v2+json;charset=UTF-8" -
此时consul中显示服务状态进入维护模式：
image-20190218164643941
-
恢复操作时，只需要将状态变更为UP即可，执行完毕后consul上的服务状态恢复：
curl -X "POST" "http://localhost:8081/actuator/service-registry?status=UP" -H "Content-Type: application/vnd.spring-boot.actuator.v2+json;charset=UTF-8"
image-20190218164921868
6、参考文档：
1、http://www.itmuch.com/spring-cloud-sum/how-to-unregister-service-in-eureka/
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