使用Zookeeper实现负载均衡轮询例子

1.原理

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。

2.实例代码相关

Maven依赖:

    <dependencies>
        <dependency>
            <groupId>com.101tec</groupId>
            <artifactId>zkclient</artifactId>
            <version>0.8</version>
        </dependency>
        <dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.4.6</version>
        </dependency>
    </dependencies>

ZkServerScoekt:

public class ZkServerScoekt implements Runnable {
    private static int port = 18081;

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

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

    public void regServer() {
        // 向ZooKeeper注册当前服务器
        ZkClient client = new ZkClient("127.0.0.1:2181", 60000, 1000);
        String path = "/test/server" + port;
        if (client.exists(path))
            client.delete(path);
        client.createEphemeral(path, "127.0.0.1:" + port);
    }

    public void run() {
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(port);
            regServer();
            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) {

            }
        }
    }

}

ZkServerClient:

public class ZkServerClient {
    public static List<String> listServer = new ArrayList<String>();

    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() {
        final String path = "/test";
        final ZkClient zkClient = new ZkClient("127.0.0.1:2181", 60000, 1000);
        List<String> children = zkClient.getChildren(path);
        listServer.clear();
        for (String p : children) {
            listServer.add((String) zkClient.readData(path + "/" + p));
        }
        // 订阅节点变化事件
        zkClient.subscribeChildChanges("/test", new IZkChildListener() {

            public void handleChildChange(String parentPath, List<String> currentChilds) throws Exception {
                listServer.clear();
                for (String p : currentChilds) {
                    listServer.add((String) zkClient.readData(path + "/" + p));
                }
                System.out.println("####handleChildChange()####listServer:" + listServer.toString());
            }
        });
    }

    // 请求次数
    private static int count = 1;
    // 服务数量
    private static int serverCount=2;

    // 获取当前server信息
    public static String getServer() {
        String serverName = listServer.get(count%serverCount);
        ++count;
        return serverName;
    }

    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();
                }
            }
        }
    }
}

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