zookeeper實作負載均衡

解析：首先會員服務在注冊中心上注冊，這個時候就在zookeeper上生成幾個臨時節點，節點名是/member/8080和/member/8081,值是127.0.0.1:8080,127.0.0.1:8081（zookeeeper每個節點都有節點名和節點值），/member是會員服務的入口，這個時候訂單服務調用會員服務，使用本地負載均衡政策，如下所示：

使用Zookeeper實作負載均衡原理

思路

使用Zookeeper實作負載均衡原理，伺服器端将啟動的服務注冊到，zk注冊中心上，采用臨時節點。用戶端從zk節點上擷取最新服務節點資訊，本地使用負載均衡算法，随機配置設定伺服器。

Maven依賴

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

建立Server服務端

ZkServerScoekt服務

package com.itmayiedu;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import org.I0Itec.zkclient.ZkClient;
//##ServerScoekt服務端
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;
	}
	// 将服務資訊注冊到注冊中心上去
	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("##服務注冊成功###"+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 {
	// 擷取所有的服務位址
	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();
			}
		}
	}
	// 注冊所有server
	public static void initServer() {
		listServer.clear();
		// 從zk擷取最新擷取的注冊服務連接配接
		final String memberServerPath = "/member";
		final ZkClient zkClient = new ZkClient("127.0.0.1:2181", 6000, 1000);
		// 獲目前下子節點
		List<String> children = zkClient.getChildren(memberServerPath);
		listServer.clear();
		for (String p : children) {
			// 讀取子節點value值
			listServer.add((String) zkClient.readData(memberServerPath + "/" + p));
		}
		System.out.println("最新服務資訊listServer:" + listServer.toString());
		// 訂閱子節點事件
		zkClient.subscribeChildChanges(memberServerPath, new IZkChildListener() {
			// 子節點發生變化
			public void handleChildChange(String parentPath, List<String> childrens) throws Exception {
				listServer.clear();
				for (String subP : childrens) {
					// 讀取子節點value值
					listServer.add((String) zkClient.readData(memberServerPath + "/" + subP));
				}
			}
		});
	}
	// 服務調用次數
	private static int count = 1;
	// 會員服務叢集數量，實際開發中不要寫死，
	private static int memberServerCount = 2;
	// 擷取目前server資訊
	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：當我們運作ZkServerScoekt.java後，再運作ZkServerClient.java,在ZkServerClient.java裡面有一個main方法，接下來說執行流程：

 這是client.send方法的定義

 接下來我們來看伺服器端的代碼分析：

 運作效果截圖：

這是zkServerClient控制台：

 這是18081伺服器控制台：

這是18080伺服器控制台： 

從以上結果可以看出，實作了負載均衡的輪詢機制

常見負載均衡算法：輪詢、權重、IP綁定