Zookeeper实现服务注册/发现

what that?

Zookeeper在分布式开发中使用频繁,但许多框架都对其进行了封装,初学者可能无法较好的理解其工作原理,该文章演示了使用Zookeeper实现服务注册,服务发现的简单demo,希望能达到抛砖引玉的效果;

why need RegisterCenter?

之所以需要访问注册和服务发现是因为分布式系统中,服务之间需要相互调用,但若每个服务自己维护一份依赖的服务信息的话,就显得很麻烦,且自身维护的数据无法保证其实时性,当依赖的服务信息发生变更时,无法及时获取更新,解决方案就是引入一个注册中心,服务提供方将自己的信息写入到注册中心,服务使用方从注册中心来获取服务信息; 如下图:

client表示服务使用方,server表示服务提供方

实现的效果: 客户端可自动发现服务信息,当服务状态发生变化时(上线,下线,更换地址),客户端可以及时响应变化,效果如下图:

效果演示

实现

首先保证Zookeeper以安装启动,且可以正常访问

创建Maven项目并添加Zookeeper的Java客户端依赖(注意版本号需>3.6)

				<dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.6.1</version>
        </dependency>

编写服务提供方

package com.jerry;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.ACL;

import java.io.IOException;
import java.io.InputStream;
import java.net.*;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Enumeration;

import static java.net.InetAddress.getLocalHost;

public class UserService {

    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        new UserService().serving();
    }

    public void serving() throws IOException, KeeperException, InterruptedException {
        //获取本机ip地址
        String ip = null;
        Enumeration<NetworkInterface> networkInterfaces = NetworkInterface.getNetworkInterfaces();
        while (networkInterfaces.hasMoreElements()) {
            NetworkInterface ni = (NetworkInterface) networkInterfaces.nextElement();
            Enumeration<InetAddress> nias = ni.getInetAddresses();
            while (nias.hasMoreElements()) {
                InetAddress ia = (InetAddress) nias.nextElement();
                if (!ia.isLinkLocalAddress() && !ia.isLoopbackAddress() && ia instanceof Inet4Address) {
                    ip = ia.getHostAddress();
                }
            }
        }
        int port = 8988;

        //启动服务
        ServerSocket socket = new ServerSocket(port);
        System.out.println("服务器已启动...");
        //注册服务
        serverRegister(ip, port);
        //处理请求
        clientHandler(socket);
    }

    private void clientHandler(ServerSocket socket) throws IOException {
        while (true) {
            Socket accept = socket.accept();
            InputStream inputStream = accept.getInputStream();
            byte[] barr = new byte[1024];
            while (true) {
                int size = inputStream.read(barr);
                if (size == -1) {
                    //System.out.println("客户端已关闭..");
                    accept.close();
                    break;
                }
                String s = new String(barr, 0, size);
                //输出客户端消息
                System.out.println(accept.getInetAddress().getHostAddress() + ": " + s);
            }
        }

    }

    private void serverRegister(String ip, int port) throws IOException, KeeperException, InterruptedException {
        //注册服务
        ZooKeeper zooKeeper = new ZooKeeper("10.211.55.4: 2181",3000, null);
        try {
            ArrayList<ACL> acl = new ArrayList<>();
            acl.add(new ACL(31, ZooDefs.Ids.ANYONE_ID_UNSAFE));
            zooKeeper.create("/userServer", (ip + ":" + port).getBytes(StandardCharsets.UTF_8), acl, CreateMode.EPHEMERAL);
            System.out.println("服务发布成功!");
        } catch (KeeperException | InterruptedException e) {
            e.printStackTrace();
            throw e;
        }
    }
}

编写服务服务使用方

package com.yyh;

import org.apache.zookeeper.*;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.util.Scanner;

public class UserClient implements Watcher {
    String node = "/userServer"; //服务信息所在的节点 服务提供方和服务消费方一致
    private ZooKeeper zooKeeper;
    String server_ip;
    int server_port;

    public static void main(String[] args) throws Exception {
        //开始服务监听
        UserClient userClient = new UserClient();
        userClient.run();
        //当访问可用时与服务交互
        Scanner scanner = new Scanner(System.in);
        while (true){
            System.out.println("输入要发送的信息(e:退出)");
            String text = scanner.next();
            if (text.equals("e"))System.exit(-1);
            if (userClient.server_ip == null){
                System.err.println("没有可用的服务...");
            }else {
                userClient.sendToServer(text);
            }
        }
    }
    
    private void run() throws Exception {
        //连接zookeeper
        zooKeeper = new ZooKeeper("10.211.55.4:2181", 3000, null);
        //尝试获取服务信息
        getServerInfo();
        //添加对服务信息的永久监听
        zooKeeper.addWatch(node,this,AddWatchMode.PERSISTENT);
    }

    //获取服务信息
    private void getServerInfo()  {
        try {
            byte[] data = zooKeeper.getData(node, false, null);
            String[] infos = new String(data).split(":");
            server_ip = infos[0];
            server_port = Integer.parseInt(infos[1]);
            System.out.println("获取服务信息成功!");
            System.out.println(server_ip+":"+ server_port);
        } catch (KeeperException e) {
            System.err.println("服务信息不存在! 等待服务上线........");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    //当节点状态发送变化时将执行该方法(通知处理)
    @Override
    public void process(WatchedEvent event) {
        if (event.getPath().equals(node)) {
            //根据具体逻辑处理不同的事件类型,此处只关心节点的创建删除和更新
            if (event.getType() == Event.EventType.NodeCreated) {
                System.err.println("服务上线了");
                getServerInfo();
            } else if (event.getType() == Event.EventType.NodeDataChanged) {
                System.err.println("服务更新了");
                getServerInfo();
            }else if (event.getType()== Event.EventType.NodeDeleted){
                server_ip = null;
                server_port = 0;
                System.err.println("服务下线了");
            }
        }
    }

    public void sendToServer(String text) {
        InetSocketAddress server_address = new InetSocketAddress(server_ip, server_port);
        Socket socket = new Socket();
        try {
            socket.connect(server_address);
            //System.out.println("连接服务器成功!");
            OutputStream outputStream = socket.getOutputStream();
            outputStream.write(text.getBytes());
            System.out.println("消息发送成功!");
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

打包服务端代码,该步骤可忽略,仅为了测试客户端正确性, 为了在打包时附带其全部依赖,此处借助Spring的打包插件,在pom中添加以下内容:

		<build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>1.5.6.RELEASE</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

注意:Spring-boot打包插件会自动获取项目中的主函数,必须保证主函数只有一个,所以需要暂时注释客户端的主函数,最后执行maven的package,得到jar包

将jar上传至虚拟机并运行
```
java -jar ZookeeperTest-1.0-SNAPSHOT.jar
```
若没有其他问题则客户端依然可以正常连接服务器发送消息;

以上便是使用Zookeeper实现服务注册和服务发现的具体步骤,在实际开发中,我们可能还会将提供的服务部署为集群,这时可将集群中的各个服务信息作为子节点注册到指定节点下,客户端监听该节点变化,获取子节点列表从而获取到服务列表,还可以在此基础上加上负载均衡算法实现对服务列表的合理访问; 如图:

posted @ 2020-06-09 10:54 CoderJerry 阅读(2014) 评论(0) 编辑收藏举报

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