分布式系列教程（10） -分布式协调工具Zookeeper（负载均衡原理实现）

代码已上传到Gtihub，有兴趣的同学可以下载来看看（git版本号90275563ea2f9efc047e62427f6b9d472fe47b7f）:https://github.com/ylw-github/Zookeeper-Demo

使用Zookeeper实现负载均衡原理：

• 服务器端将启动的服务注册到ZK注册中心上，采用临时节点。
• 客户端从zk节点上获取最新服务节点信息，本地使用负载均衡算法，随机分配服务器。

下面来开始讲解代码的实现

ZK负载均衡实现 传统模式

1.添加maven依赖：

    org.apache.zookeeper
    zookeeper
    3.4.6



    com.101tec
    zkclient
    0.8

2.创建Server服务端:

ZkServerScoekt服务：

package com.ylw.zookeeper.loadbalance;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class ZkServerScoekt implements Runnable {

    private int port = 18080;

    public ZkServerScoekt(int port) {
        this.port = port;
    }

    public void run() {
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(port);
            System.out.println("Server start port:" + port);
            Socket socket = null;
            while (true) {
                socket = serverSocket.accept();
                new Thread(new ServerHandler(socket)).start();
            }
        } catch (Exception e) {
            e.printStackTrace();

        } finally {
            try {
                if (serverSocket != null) {
                    serverSocket.close();
                }
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws IOException {
        int port = 18080;
        ZkServerScoekt server = new ZkServerScoekt(port);
        Thread thread = new Thread(server);
        thread.start();
    }
}

ServerHandler:

package com.ylw.zookeeper.loadbalance;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

public class ServerHandler implements Runnable {
    private Socket socket;

    public ServerHandler(Socket socket) {
        this.socket = socket;
    }

    public void run() {
        BufferedReader in = null;
        PrintWriter out = null;
        try {
            in = new BufferedReader(new InputStreamReader(this.socket.getInputStream()));
            out = new PrintWriter(this.socket.getOutputStream(), true);
            String body = null;
            while (true) {
                body = in.readLine();
                if (body == null)
                    break;
                System.out.println("Receive : " + body);
                out.println("Hello, " + body);
            }

        } catch (Exception e) {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }
            if (out != null) {
                out.close();
            }
            if (this.socket != null) {
                try {
                    this.socket.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
                this.socket = null;
            }
        }
    }
}

3.创建客户端ZkServerClient:

package com.ylw.zookeeper.loadbalance;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;

public class ZkServerClient {

    public static List listServer = new ArrayList();

    public static void main(String[] args) {
        initServer();
        ZkServerClient client = new ZkServerClient();
        BufferedReader console = new BufferedReader(new InputStreamReader(System.in));
        while (true) {
            String name;
            try {
                name = console.readLine();
                if ("exit".equals(name)) {
                    System.exit(0);
                }
                client.send(name);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    // 注册所有server
    public static void initServer() {
        listServer.clear();
        listServer.add("127.0.0.1:18080");
    }

    // 获取当前server信息
    public static String getServer() {
        return listServer.get(0);
    }

    public void send(String name) {

        String server = ZkServerClient.getServer();
        String[] cfg = server.split(":");

        Socket socket = null;
        BufferedReader in = null;
        PrintWriter out = null;
        try {
            socket = new Socket(cfg[0], Integer.parseInt(cfg[1]));
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out = new PrintWriter(socket.getOutputStream(), true);

            out.println(name);
            while (true) {
                String resp = in.readLine();
                if (resp == null)
                    break;
                else if (resp.length() > 0) {
                    System.out.println("Receive : " + resp);
                    break;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (out != null) {
                out.close();
            }
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

4. 运行Server和Client

客户端控制台输入并发送：Hello ,I am YLW ! 服务端接收：

使用Zookeeper

1.改造ZkServerScoekt

package com.ylw.zookeeper.loadbalance;

import org.I0Itec.zkclient.ZkClient;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class ZkServerScoekt2 implements Runnable {

    private static int port = 18081;  //socket 服务启动后的所使用的 端口号

    public static void main(String[] args) throws IOException {
        ZkServerScoekt server = new ZkServerScoekt(port);  //构造函数传入port
        regServer();  //去zk注册
        Thread thread = new Thread(server);
        thread.start();
    }

    public ZkServerScoekt2(int port) {
        this.port = port;
    }

    //注册服务
    public static void regServer() {
        //1、建立zk连接
        ZkClient zkClient = new ZkClient("192.168.162.131", 5000, 10000);
        //2.先创建父节点
        String root = "/toov5";
        if (!zkClient.exists(root)) {
            //如果父节点不存，直接创建父节点
            zkClient.createPersistent(root);  //持久节点
        }
        //3、创建子节点
        String nodeName = root + "/service_" + port;
        String nodeValue = "127.0.0.1:" + port;
        if (zkClient.exists(nodeName)) {  //如果存在 直接删除掉
            zkClient.delete(nodeName);
        }
        zkClient.createEphemeral(nodeName, "127.0.0.1:" + port);
        System.out.println("服务注册成功" + nodeName);

    }


    public void run() {
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(port);
            System.out.println("Server start port:" + port);
            Socket socket = null;
            while (true) {
                socket = serverSocket.accept();
                new Thread(new ServerHandler(socket)).start();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (serverSocket != null) {
                    serverSocket.close();
                }
            } catch (Exception e2) {

            }
        }
    }
}

改造ZkServerClient：

package com.ylw.zookeeper.loadbalance;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;

public class ZkServerClient2 {

    public static List listServer = new ArrayList();

    public static void main(String[] args) {
        initServer();
        ZkServerClient2 client = new ZkServerClient2();
        BufferedReader console = new BufferedReader(new InputStreamReader(System.in));
        while (true) {
            String name;
            try {
                name = console.readLine();
                if ("exit".equals(name)) {
                    System.exit(0);
                }
                client.send(name);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    // 注册所有server
    public static void initServer() {
        listServer.clear();
        listServer.add("127.0.0.1:18081"); //连接服务 放到list中   存放集群地址 做负载均衡用的
    }

    // 获取当前server信息
    public static String getServer() {
        return listServer.get(0);
    }

    public void send(String name) {

        String server = ZkServerClient2.getServer();
        String[] cfg = server.split(":");

        Socket socket = null;
        BufferedReader in = null;
        PrintWriter out = null;
        try {
            socket = new Socket(cfg[0], Integer.parseInt(cfg[1]));
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out = new PrintWriter(socket.getOutputStream(), true);

            out.println(name);
            while (true) {
                String resp = in.readLine();
                if (resp == null)
                    break;
                else if (resp.length() > 0) {
                    System.out.println("Receive : " + resp);
                    break;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (out != null) {
                out.close();
            }
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

}

参考：https://www.cnblogs.com/toov5/p/9899238.html