ZooKeeper 使用场景之负载均衡

男娘i 2022-02-28 01:36 239阅读 0赞

### 前言 ###

上章,我们简单了解了下`ZooKeeper`内的成员变量及调度服务.本章主要讲解下`ZooKeeper`的负载均衡.

--------------------

### 正文 ###

假设我们有3台服务器用于负载.那么有一台`Client`,其该怎么链接哪台机器呢?当其链接的主机宕机后该链接哪台服务器呢?我们可以使用`Nginx`或`KeepAlive`或者`心跳机制`.而使用今天的主角`ZooKeeper`,其也可以实现.

原始架构:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70]  
新架构:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 1]

*  服务器结点: 可以在`ZooKeeper`集群内存储一个`/servers`的目录结构.各个结点的负载存储如下:`/servers/servers1 <int>`.
 *  客户端结点: 可以通过`ZooKeeper`集群寻找负载最小的结点.此外,还可以设置监听器, 当`server`结点宕机后,`ZooKeeper`将删除服务器结点目录,`Client`结点收到通知,重新进行负载.
 *  Tips: 创建的ZooKeeper结点皆为临时结点.(详见ZooKeeper结点类型)

--------------------

### 编码 ###

> DistributedServer

package com.yanxml.zookeeper.demos.server;
    
    import java.io.IOException;
    
    import org.apache.zookeeper.CreateMode;
    import org.apache.zookeeper.KeeperException;
    import org.apache.zookeeper.WatchedEvent;
    import org.apache.zookeeper.Watcher;
    import org.apache.zookeeper.ZooKeeper;
    import org.apache.zookeeper.data.Stat;
    import org.apache.zookeeper.ZooDefs.Ids;
    
    /**
     * 分布式上线集群.(服务端)
     * com.yanxml.zookeeper.demos.server.DistributedServer
     * */
    public class DistributedServer {
    	private static final String connectString = "192.168.31.60:2181,192.168.31.61:2181,192.168.31.62:2181";
    	private static final int sessionTimeout = 2000;
    	private static final String parentNode = "/servers/"; 
    	
    	private ZooKeeper zk = null;
    	
    	public void getConnect() throws IOException{
    		zk = new ZooKeeper(connectString, sessionTimeout, new Watcher(){
    
    			@Override
    			public void process(WatchedEvent event) {
    				// 收到事件通知后的回调函数(我们自己的处理逻辑)
    				System.out.println(event.getType()+"---"+event.getPath());
    				try{
    					zk.getChildren("/", true);
    				}catch(Exception e){
    					
    				}
    			}
    			
    		});
    	}
    	
    	// 进行父节点检测 (这边只做单层的结点判断 - 如果多层的话也可以进行判断.)
    	public boolean parntNodeCheck() throws KeeperException, InterruptedException{
    		boolean flag = true;
            Stat exists = zk.exists(parentNode.substring(0, parentNode.length()-1), false);
            if(null == exists){
        		String create = zk.create(parentNode.substring(0, parentNode.length()-1), parentNode.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        		System.out.println(parentNode+"is init...." + create);
            }
    		return flag;
    	}
    	
    	//	创建到zk的客户端链接. 
    	public void registerServer(String hostname) throws KeeperException, InterruptedException{
    		parntNodeCheck();
    		String create = zk.create(parentNode+hostname, hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
    		System.out.println(hostname+"is online...." + create);
    	}
    	
    	// 业务功能
    	public void handleBussiness(String hostname){
    		System.out.println(hostname + " is working...");
    		// 实现死循环(让业务一直运行下去.)
    		while(true){
    			
    		}
    	}
    
    	
    	public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
    		// 获取ZK链接
    		DistributedServer servier = new DistributedServer();
    		servier.getConnect();
    		
    		
    		if(null != args[0]){
    			servier.registerServer(args[0]);
    			servier.handleBussiness(args[0]);
    		}
    		
    //		System.out.println(parentNode.substring(0, parentNode.length()-1));
    		
    		
    	}
    }

> DistributedClient

package com.yanxml.zookeeper.demos.server;
    
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;
    
    import org.apache.zookeeper.KeeperException;
    import org.apache.zookeeper.WatchedEvent;
    import org.apache.zookeeper.Watcher;
    import org.apache.zookeeper.ZooKeeper;
    
    /**
     * 分布式上线集群.(客户端)
     * 
     * */
    
    public class DistributedClient {
    	private static final String connectString = "192.168.31.60:2181,192.168.31.61:2181,192.168.31.62:2181";
    	private static final int sessionTimeout = 2000;
    	private static final String parentNode = "/servers"; 
    	
    	// volatile 意义(多线程使用时候使用.)
    	private volatile List<String> serverList;
    	
    	private ZooKeeper zk = null;
    	
    	public void getConnect() throws IOException{
    		zk = new ZooKeeper(connectString, sessionTimeout, new Watcher(){
    
    			@Override
    			public void process(WatchedEvent event) {
    				// 收到事件通知后的回调函数(我们自己的处理逻辑)
    				System.out.println(event.getType()+"---"+event.getPath());
    				try{
    					// 重新更新服务器列表.并且注册了监听
    					getServerList();
    				}catch(Exception e){
    					
    				}
    			}
    			
    		});
    	}
    	
    	public void getServerList() throws KeeperException, InterruptedException{
    		// 获取服务器子结点信息 并对父结点进行监听
    		List<String> children = zk.getChildren(parentNode, true);
    		
    		// 创建一个局部的list来存储服务器信息
    		List<String> servers = new ArrayList<>();
    		for(String child:children){
    			// child是子结点的结点名称
    			byte[] data = zk.getData(parentNode+"/"+child, false, null);
    			servers.add(new String(data));
    		}
    		// 把 servers赋值给成员变量serverlist,以提供给各个线程使用. 
    		serverList = servers;
    		
    		// 打印下服务器列表
    		System.out.println(serverList);
    	}
    	
    	// 业务功能
    	public void handleBussiness(){
    		System.out.println("Client" + " is working...");
    		// 实现死循环(让业务一直运行下去.)
    		while(true){
    			
    		}
    	}
    	
    	public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
    		// 获取zk链接
    		DistributedClient client = new DistributedClient();
    		client.getConnect();
    		// 获取servers的子结点信息(并监听),从中获取服务器信息列表
    		client.getServerList();
    		
    		// 业务线程启动
    		client.handleBussiness();
    	}
    }

--------------------

### 运行 ###

我们使用`Maven`打包后,分别带参数启动.

# 启动服务器2
    localhost:target Sean$ java -cp zookeeper-0.0.1-SNAPSHOT.jar com.yanxml.zookeeper.demos.server.DistributedServer mac1
    Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF-8
    2019-03-23 18:01:54,945 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:zookeeper.version=3.4.6-1569965, built on 02/20/2014 09:09 GMT
    2019-03-23 18:01:54,946 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:host.name=localhost
    2019-03-23 18:01:54,946 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.version=1.8.0_102
    2019-03-23 18:01:54,946 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.vendor=Oracle Corporation
    2019-03-23 18:01:54,946 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.home=/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre
    2019-03-23 18:01:54,946 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.class.path=zookeeper-0.0.1-SNAPSHOT.jar
    2019-03-23 18:01:54,946 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.library.path=/Users/Sean/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.
    2019-03-23 18:01:54,946 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.io.tmpdir=/var/folders/lm/j_tf25pd1bn1lvf3nm1qkjd40000gn/T/
    2019-03-23 18:01:54,947 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.compiler=<NA>
    2019-03-23 18:01:54,947 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:os.name=Mac OS X
    2019-03-23 18:01:54,947 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:os.arch=x86_64
    2019-03-23 18:01:54,947 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:os.version=10.14
    2019-03-23 18:01:54,947 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:user.name=Sean
    2019-03-23 18:01:54,948 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:user.home=/Users/Sean
    2019-03-23 18:01:54,948 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:user.dir=/Users/Sean/Documents/Gitrep/bigdata/zookeeper/target
    2019-03-23 18:01:54,951 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Initiating client connection, connectString=192.168.31.60:2181,192.168.31.61:2181,192.168.31.62:2181 sessionTimeout=2000 watcher=com.yanxml.zookeeper.demos.server.DistributedServer$1@5d099f62
    2019-03-23 18:01:54,988 [main-SendThread(192.168.31.60:2181)] INFO  [org.apache.zookeeper.ClientCnxn] - Opening socket connection to server 192.168.31.60/192.168.31.60:2181. Will not attempt to authenticate using SASL (unknown error)
    2019-03-23 18:01:55,119 [main-SendThread(192.168.31.60:2181)] INFO  [org.apache.zookeeper.ClientCnxn] - Socket connection established to 192.168.31.60/192.168.31.60:2181, initiating session
    2019-03-23 18:01:55,145 [main-SendThread(192.168.31.60:2181)] INFO  [org.apache.zookeeper.ClientCnxn] - Session establishment complete on server 192.168.31.60/192.168.31.60:2181, sessionid = 0x169a99d0b810003, negotiated timeout = 4000
    None---null
    mac1is online..../servers/mac1
    mac1 is working...
    
    
    # 启动服务器1
    localhost:target Sean$ java -cp zookeeper-0.0.1-SNAPSHOT.jar com.yanxml.zookeeper.demos.server.DistributedServer mac0
    Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF-8
    2019-03-23 18:01:51,870 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:zookeeper.version=3.4.6-1569965, built on 02/20/2014 09:09 GMT
    2019-03-23 18:01:51,871 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:host.name=localhost
    2019-03-23 18:01:51,871 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.version=1.8.0_102
    2019-03-23 18:01:51,871 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.vendor=Oracle Corporation
    2019-03-23 18:01:51,871 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.home=/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre
    2019-03-23 18:01:51,871 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.class.path=zookeeper-0.0.1-SNAPSHOT.jar
    2019-03-23 18:01:51,871 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.library.path=/Users/Sean/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.
    2019-03-23 18:01:51,871 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.io.tmpdir=/var/folders/lm/j_tf25pd1bn1lvf3nm1qkjd40000gn/T/
    2019-03-23 18:01:51,871 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.compiler=<NA>
    2019-03-23 18:01:51,872 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:os.name=Mac OS X
    2019-03-23 18:01:51,872 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:os.arch=x86_64
    2019-03-23 18:01:51,872 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:os.version=10.14
    2019-03-23 18:01:51,872 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:user.name=Sean
    2019-03-23 18:01:51,872 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:user.home=/Users/Sean
    2019-03-23 18:01:51,872 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:user.dir=/Users/Sean/Documents/Gitrep/bigdata/zookeeper/target
    2019-03-23 18:01:51,874 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Initiating client connection, connectString=192.168.31.60:2181,192.168.31.61:2181,192.168.31.62:2181 sessionTimeout=2000 watcher=com.yanxml.zookeeper.demos.server.DistributedServer$1@5d099f62
    2019-03-23 18:01:51,908 [main-SendThread(192.168.31.62:2181)] INFO  [org.apache.zookeeper.ClientCnxn] - Opening socket connection to server 192.168.31.62/192.168.31.62:2181. Will not attempt to authenticate using SASL (unknown error)
    2019-03-23 18:01:52,040 [main-SendThread(192.168.31.62:2181)] INFO  [org.apache.zookeeper.ClientCnxn] - Socket connection established to 192.168.31.62/192.168.31.62:2181, initiating session
    2019-03-23 18:01:52,079 [main-SendThread(192.168.31.62:2181)] INFO  [org.apache.zookeeper.ClientCnxn] - Session establishment complete on server 192.168.31.62/192.168.31.62:2181, sessionid = 0x369a99d1a8d0002, negotiated timeout = 4000
    None---null
    mac0is online..../servers/mac0
    mac0 is working...
    
    # 启动客户端
    localhost:target Sean$ java -cp zookeeper-0.0.1-SNAPSHOT.jar com.yanxml.zookeeper.demos.server.DistributedClient
    Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF-8
    2019-03-23 18:01:47,117 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:zookeeper.version=3.4.6-1569965, built on 02/20/2014 09:09 GMT
    2019-03-23 18:01:47,118 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:host.name=localhost
    2019-03-23 18:01:47,118 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.version=1.8.0_102
    2019-03-23 18:01:47,118 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.vendor=Oracle Corporation
    2019-03-23 18:01:47,118 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.home=/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home/jre
    2019-03-23 18:01:47,118 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.class.path=zookeeper-0.0.1-SNAPSHOT.jar
    2019-03-23 18:01:47,118 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.library.path=/Users/Sean/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.
    2019-03-23 18:01:47,118 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.io.tmpdir=/var/folders/lm/j_tf25pd1bn1lvf3nm1qkjd40000gn/T/
    2019-03-23 18:01:47,118 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:java.compiler=<NA>
    2019-03-23 18:01:47,119 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:os.name=Mac OS X
    2019-03-23 18:01:47,119 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:os.arch=x86_64
    2019-03-23 18:01:47,119 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:os.version=10.14
    2019-03-23 18:01:47,119 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:user.name=Sean
    2019-03-23 18:01:47,119 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:user.home=/Users/Sean
    2019-03-23 18:01:47,119 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Client environment:user.dir=/Users/Sean/Documents/Gitrep/bigdata/zookeeper/target
    2019-03-23 18:01:47,120 [main] INFO  [org.apache.zookeeper.ZooKeeper] - Initiating client connection, connectString=192.168.31.60:2181,192.168.31.61:2181,192.168.31.62:2181 sessionTimeout=2000 watcher=com.yanxml.zookeeper.demos.server.DistributedClient$1@5d099f62
    2019-03-23 18:01:47,155 [main-SendThread(192.168.31.61:2181)] INFO  [org.apache.zookeeper.ClientCnxn] - Opening socket connection to server 192.168.31.61/192.168.31.61:2181. Will not attempt to authenticate using SASL (unknown error)
    2019-03-23 18:01:47,244 [main-SendThread(192.168.31.61:2181)] INFO  [org.apache.zookeeper.ClientCnxn] - Socket connection established to 192.168.31.61/192.168.31.61:2181, initiating session
    2019-03-23 18:01:47,268 [main-SendThread(192.168.31.61:2181)] INFO  [org.apache.zookeeper.ClientCnxn] - Session establishment complete on server 192.168.31.61/192.168.31.61:2181, sessionid = 0x269a99d0b8c0003, negotiated timeout = 4000
    None---null
    []
    []
    Client is working...
    -- 关闭服务器2
    NodeChildrenChanged---/servers
    [mac0]
    -- 启动服务器2(自动感知)
    NodeChildrenChanged---/servers
    [mac1, mac0]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70]: /images/20220228/dc80e5c8d258440ca07975cd5ee4552a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly95YW54bWwuYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 1]: /images/20220228/0d8e36fe9c044c599393a8e81b73004a.png