SpringCloud使用Consul时,服务注销的操作方式

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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_SERVICE

    curl -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、www.itmuch.com/spring-clou…

2、blog.51cto.com/qiangmzsx/2…