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server
public 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
使用Zookeeper实现选举策略
解析:谁先在zookeeper上创建临时节点,谁就为主节点(太上皇),如果主节点挂了,那么就从剩下的从节点中(事件监听到主挂了)开始比赛,谁先创建临时节点,谁就为主(皇上),(就算太上皇活了,也只能为从,服从新皇的指挥)