基于ZooKeeper的服务注册实现

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简介

本文介绍在Spring Boot环境下，使用ZooKeeper来注册服务。在本地环境搭建了ZooKeeper的伪集群环境。

本文参考了《架构探险》轻量级微服务架构这本书。

搭建ZooKeeper伪集群

下载并安装

在官网下载ZooKeeper相关包后，解压到/etc/zookeeper下，并复制3份（ZooKeeper构建集群时，官网建议部署奇数个节点）。
安装ZooKeeper

修改配置

将conf/zoo_sample.cfg重命名为zoo.cfg,并将节点1修改为如下配置，具体意思请百度，这里不详细展开，因为这里配置的伪集群，所以要求各端口都不一样。

注意：在路径/home/billjiang/zookeeper/zkServer1目录下需要建立一个myid文件，并在文件中写入内容1

节点1配置

# The number of milliseconds of each ticktickTime=2000initLimit=10syncLimit=5dataDir=/home/billjiang/zookeeper/zkServer1clientPort=2181#clusterserver.1=127.0.0.1:2888:3888server.2=127.0.0.1:2889:3889server.3=127.0.0.1:2890:3890

节点2配置

# The number of milliseconds of each ticktickTime=2000initLimit=10syncLimit=5dataDir=/home/billjiang/zookeeper/zkServer2clientPort=2182#clusterserver.1=127.0.0.1:2888:3888server.2=127.0.0.1:2889:3889server.3=127.0.0.1:2890:3890

节点3配置

# The number of milliseconds of each ticktickTime=2000initLimit=10syncLimit=5dataDir=/home/billjiang/zookeeper/zkServer3clientPort=2183#clusterserver.1=127.0.0.1:2888:3888server.2=127.0.0.1:2889:3889server.3=127.0.0.1:2890:3890

批量启动集群shell脚本

为了启动集群，可以一个一个启动，也可以编写shell脚本批量启动：

zookeeper_start.sh

    #!/bin/bash      SERVERS="zkServer1 zkServer2 zkServer3"      for SERVER in $SERVERS      do            echo "当前"$SERVER"正在启动...................."             #ssh root@$SERVER "source /etc/profile;/usr/apps/zookeeper-3.4.9/bin/zkServer.sh start"            sudo /etc/zookeeper/$SERVER/bin/zkServer.sh start          echo $SERVER"启动结束--------------------------------------------"                                                                             done

当然也可以编写批量停止的shell脚本。执行批量启动命令后，如下：
启动ZooKeeper集群

启动集群后，可使用bin/zkCli.sh命令查看ZooKeeper的节点数据。

以上完成了ZooKeeper伪集群的搭建。

服务注册实现

为了演示服务在ZooKeeper上的注册过程，本文这里启动了一个Maven项目zookeeper-learn,项目包含三个module

core 注册的核心逻辑
client 客户端服务1
client2 客户端服务2

zookeeper-learn

其中client/client2项目都依赖了core项目。在它们的pom.xml配置了该依赖

<dependency>            <groupId>com.cnpc</groupId>            <artifactId>core</artifactId>            <version>0.0.1-SNAPSHOT</version></dependency>

core项目的核心代码

定义服务注册接口ServiceRegistry

package com.example.core;public interface ServiceRegistry {    /**     * 注册服务信息     *     * @param serviceName    服务名称     * @param serviceAddress 服务地址     */    void register(String serviceName, String serviceAddress);}

服务注册实现ServiceRegistryImpl
该服务实现将连接ZooKeeper集群，创建节点，并把服务的调用地址作为节点的值存储在该节点上。

package com.example.core;import org.apache.zookeeper.*;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.stereotype.Component;import java.util.concurrent.CountDownLatch;@Componentpublic class ServiceRegistryImpl implements ServiceRegistry, Watcher {    private static Logger logger = LoggerFactory.getLogger(ServiceRegistryImpl.class);    private static CountDownLatch latch = new CountDownLatch(1);    private ZooKeeper zk;    private static final int SESSION_TIMEOUT = 5000;    public ServiceRegistryImpl() {    }    public ServiceRegistryImpl(String zkServers) {        try {            zk = new ZooKeeper(zkServers, SESSION_TIMEOUT, this);            latch.await();            logger.debug("connected to zookeeper");        } catch (Exception ex) {            logger.error("create zookeeper client failure", ex);        }    }    private static final String REGISTRY_PATH = "/registry";    @Override    public void register(String serviceName, String serviceAddress) {        try {            String registryPath = REGISTRY_PATH;            if (zk.exists(registryPath, false) == null) {                zk.create(registryPath, null, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);                logger.debug("create registry node:{}", registryPath);            }            //创建服务节点（持久节点）            String servicePath = registryPath + "/" + serviceName;            if (zk.exists(servicePath, false) == null) {                zk.create(servicePath, null, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);                logger.debug("create service node:{}", servicePath);            }            //创建地址节点            String addressPath = servicePath + "/address-";            String addressNode = zk.create(addressPath, serviceAddress.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);            logger.debug("create address node:{} => {}", addressNode, serviceAddress);        } catch (Exception e) {            logger.error("create node failure", e);        }    }    @Override    public void process(WatchedEvent watchedEvent) {        if (watchedEvent.getState() == Event.KeeperState.SyncConnected)            latch.countDown();    }}

客户端注册服务

客户端在启动时，会将自身服务节点注册到ZooKeeper集群中。

application.properties配置

server.address=127.0.0.1server.port=8080registry.servers=127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183

服务注册配置RegistryConfig
这样客户端可以读取appliaction.properties的ZooKeeper配置

package com.example.client;import com.example.core.ServiceRegistry;import com.example.core.ServiceRegistryImpl;import org.springframework.boot.context.properties.ConfigurationProperties;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;@Configuration@ConfigurationProperties(prefix = "registry")public class RegistryConfig {    private String servers;    @Bean    public ServiceRegistry serviceRegistry() {        return new ServiceRegistryImpl(servers);    }    public void setServers(String servers) {        this.servers = servers;    }}

用来测试的服务接口：TestController

@RestControllerpublic class TestController {    @RequestMapping(name="HelloService",method = RequestMethod.GET,path = "/hello")    public String hello(){        return "Hello";    }}

在项目启动的时候会将注解中name属性有值的方法注册到ZooKeeper集群中，

package com.example.client;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Value;import org.springframework.context.ApplicationContext;import org.springframework.stereotype.Component;import javax.servlet.ServletContext;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;import com.example.core.ServiceRegistry;import org.springframework.web.context.support.WebApplicationContextUtils;import org.springframework.web.method.HandlerMethod;import org.springframework.web.servlet.mvc.method.RequestMappingInfo;import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;import java.util.Map;@Componentpublic class WebListener implements ServletContextListener {    @Value("${server.address}")    private String serverAddress;    @Value("${server.port}")    private int serverPort;    @Autowired    public ServiceRegistry serviceRegistry;    @Override    public void contextInitialized(ServletContextEvent sce) {        ServletContext servletContext=sce.getServletContext();        ApplicationContext applicationContext= WebApplicationContextUtils.getRequiredWebApplicationContext(servletContext);        RequestMappingHandlerMapping mapping=applicationContext.getBean(RequestMappingHandlerMapping.class);        Map<RequestMappingInfo,HandlerMethod> infoMap=mapping.getHandlerMethods();        for (RequestMappingInfo info : infoMap.keySet()) {            String serviceName=info.getName();            System.out.println("-----------------"+serviceName);            if(serviceName!=null){                //注册服务                serviceRegistry.register(serviceName,String.format("%s:%d",serverAddress,serverPort));            }        }    }    @Override    public void contextDestroyed(ServletContextEvent sce) {    }}

同样在client2项目中，相同的代码，唯一的区别就是client2的application.properties的server.port=8082

同时启动两个client2项目后，通过bin/zkCli.sh命令，连接到任意的一台ZooKeeper节点（因为ZooKeeper几点之间数据会保持同步）。显示如下信息：

[zk: localhost:2181(CONNECTED) 18] ls /registry/HelloService[address-0000000004, address-0000000003]

使用get查看子节点的值

get /registry/HelloService/address-0000000003127.0.0.1:8080cZxid = 0x100000026ctime = Wed Aug 09 18:00:56 CST 2017mZxid = 0x100000026mtime = Wed Aug 09 18:00:56 CST 2017pZxid = 0x100000026cversion = 0dataVersion = 0aclVersion = 0ephemeralOwner = 0x15dc5782fe8000ddataLength = 14numChildren = 0

get /registry/HelloService/address-0000000004127.0.0.1:8081cZxid = 0x100000028ctime = Wed Aug 09 18:03:05 CST 2017mZxid = 0x100000028mtime = Wed Aug 09 18:03:05 CST 2017pZxid = 0x100000028cversion = 0dataVersion = 0aclVersion = 0ephemeralOwner = 0x15dc5782fe8000edataLength = 14numChildren = 0

当停掉一台客户端client后，再次使用ls 命令，只显示address-0000000004

以上代码完成了ZooKeeper的服务注册。

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