zookeeper实现负载均衡

解析：首先会员服务在注册中心上注册，这个时候就在zookeeper上生成几个临时节点，节点名是/member/8080和/member/8081,值是127.0.0.1:8080,127.0.0.1:8081（zookeeeper每个节点都有节点名和节点值），/member是会员服务的入口，这个时候订单服务调用会员服务，使用本地负载均衡策略，如下所示：

使用Zookeeper实现负载均衡原理

思路
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。
Maven依赖

    <dependencies><dependency><groupId>com.101tec</groupId><artifactId>zkclient</artifactId><version>0.8</version></dependency></dependencies>

创建Server服务端

ZkServerScoekt服务

package com.itmayiedu;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import org.I0Itec.zkclient.ZkClient;
//##ServerScoekt服务端
public class ZkServerScoekt implements Runnable {private int port = 18080;public static void main(String[] args) throws IOException {int port = 18080;ZkServerScoekt server = new ZkServerScoekt(port);Thread thread = new Thread(server);thread.start();}public ZkServerScoekt(int port) {this.port = port;}// 将服务信息注册到注册中心上去public void regServer() {ZkClient zkClient = new ZkClient("127.0.0.1:2181", 6000, 1000);String path = "/member/server-" + port;if (zkClient.exists(path)) {zkClient.delete(path);}String value="127.0.0.1:" + port;zkClient.createEphemeral(path, "127.0.0.1:" + port);System.out.println("##服务注册成功###"+value);}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) {}}}
}

ServerHandler.java

package com.itmayiedu;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;//ServerHandler
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;}}}
}

ZkServerClient

package com.itmayiedu;
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;
import org.I0Itec.zkclient.IZkChildListener;
import org.I0Itec.zkclient.ZkClient;
public class ZkServerClient {// 获取所有的服务地址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serverpublic static void initServer() {listServer.clear();// 从zk获取最新获取的注册服务连接final String memberServerPath = "/member";final ZkClient zkClient = new ZkClient("127.0.0.1:2181", 6000, 1000);// 获当前下子节点List<String> children = zkClient.getChildren(memberServerPath);listServer.clear();for (String p : children) {// 读取子节点value值listServer.add((String) zkClient.readData(memberServerPath + "/" + p));}System.out.println("最新服务信息listServer:" + listServer.toString());// 订阅子节点事件zkClient.subscribeChildChanges(memberServerPath, new IZkChildListener() {// 子节点发生变化public void handleChildChange(String parentPath, List<String> childrens) throws Exception {listServer.clear();for (String subP : childrens) {// 读取子节点value值listServer.add((String) zkClient.readData(memberServerPath + "/" + subP));}}});}// 服务调用次数private static int count = 1;// 会员服务集群数量，实际开发中不要写死，private static int memberServerCount = 2;// 获取当前server信息public static String getServer() {String serverName = listServer.get(count % memberServerCount);++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();}}}}
}

解析：当我们运行ZkServerScoekt.java后，再运行ZkServerClient.java,在ZkServerClient.java里面有一个main方法，接下来说执行流程：

这是client.send方法的定义

接下来我们来看服务器端的代码分析：

运行效果截图：
这是zkServerClient控制台：

这是18081服务器控制台：

这是18080服务器控制台：

从以上结果可以看出，实现了负载均衡的轮询机制

常见负载均衡算法：轮询、权重、IP绑定