基于ZooKeeper的服务注册实现

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）。

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 tick
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/home/billjiang/zookeeper/zkServer1
clientPort=2181
#cluster
server.1=127.0.0.1:2888:3888
server.2=127.0.0.1:2889:3889
server.3=127.0.0.1:2890:3890

节点2配置

# The number of milliseconds of each tick
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/home/billjiang/zookeeper/zkServer2
clientPort=2182
#cluster
server.1=127.0.0.1:2888:3888
server.2=127.0.0.1:2889:3889
server.3=127.0.0.1:2890:3890

节点3配置

# The number of milliseconds of each tick
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/home/billjiang/zookeeper/zkServer3
clientPort=2183
#cluster
server.1=127.0.0.1:2888:3888
server.2=127.0.0.1:2889:3889
server.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 startecho $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

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;@Component
public 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";@Overridepublic 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);}}@Overridepublic 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=127.0.0.1
server.port=8080
registry.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;@Beanpublic ServiceRegistry serviceRegistry() {return new ServiceRegistryImpl(servers);}public void setServers(String servers) {this.servers = servers;}
}

用来测试的服务接口：TestController

@RestController
public 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;@Component
public class WebListener implements ServletContextListener {@Value("${server.address}")private String serverAddress;@Value("${server.port}")private int serverPort;@Autowiredpublic ServiceRegistry serviceRegistry;@Overridepublic 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));}}}@Overridepublic 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-0000000003
127.0.0.1:8080
cZxid = 0x100000026
ctime = Wed Aug 09 18:00:56 CST 2017
mZxid = 0x100000026
mtime = Wed Aug 09 18:00:56 CST 2017
pZxid = 0x100000026
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x15dc5782fe8000d
dataLength = 14
numChildren = 0

get /registry/HelloService/address-0000000004
127.0.0.1:8081
cZxid = 0x100000028
ctime = Wed Aug 09 18:03:05 CST 2017
mZxid = 0x100000028
mtime = Wed Aug 09 18:03:05 CST 2017
pZxid = 0x100000028
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x15dc5782fe8000e
dataLength = 14
numChildren = 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。