zookeeper

环境准备

至少2台zookeeper的集群，启动zkServer.sh start

eclipse环境要可以连接zookeeper的集群

1.zookeeper 增删盖茶

package cn.itcast.bigdata.zk;

import java.io.IOException;
import java.util.List;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import org.junit.Before;
import org.junit.Test;

public class SimpleZkClient {

    private static final String connectString = "h42:2181,h43:2181";
    private static final int sessionTimeout = 2000;

    ZooKeeper zkClient = null;

    @Before
    public void init() throws Exception {
        zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                // 收到事件通知后的回调函数（应该是我们自己的事件处理逻辑）
                System.out.println(event.getType() + "---" + event.getPath());
                try {
                    zkClient.getChildren("/", true);
                } catch (Exception e) {
                }
            }
        });

    }

    /**
     * 数据的增删改查
     * 
     * @throws InterruptedException
     * @throws KeeperException
     */

    // 创建数据节点到zk中
//    @Test
    public void testCreate() throws KeeperException, InterruptedException {
        // 参数1：要创建的节点的路径 参数2：节点大数据 参数3：节点的权限 参数4：节点的类型
        String nodeCreated = zkClient.create("/eclipse", "hellozk".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        //上传的数据可以是任何类型，但都要转成byte[]
    }

    //判断znode是否存在
//    @Test    
    public void testExist() throws Exception{
        Stat stat = zkClient.exists("/eclipse", false);
        try {
            System.out.println(stat==null?"not exist":"exist");
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        
    }
    
    // 获取子节点
//    @Test
    public void getChildren() throws Exception {
        List<String> children = zkClient.getChildren("/", true);
        for (String child : children) {
            System.out.println(child);
        }
        Thread.sleep(Long.MAX_VALUE);
    }

    //获取znode的数据
    @Test
    public void getData() throws Exception {
        
        byte[] data = zkClient.getData("/eclipse", false, null);
        System.out.println(new String(data));
        
    }
    
    //删除znode
//    @Test
    public void deleteZnode() throws Exception {
        
        //参数2：指定要删除的版本，-1表示删除所有版本
        zkClient.delete("/eclipse", -1);
        
        
    }
    //删除znode
    @Test
    public void setData() throws Exception {
        
        zkClient.setData("/app1", "imissyou angelababy".getBytes(), -1);
        
        byte[] data = zkClient.getData("/app1", false, null);
        System.out.println(new String(data));
        
    }
    
    
}

2. 用zookeeper实现 client监听集群服务器的心跳的功能。

package cn.itcast.bigdata.zkdist;

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;

public class DistributedClient {

    private static final String connectString = "h42:2181,h43:2181";
    private static final int sessionTimeout = 2000;
    private static final String parentNode = "/servers";
    // 注意:加volatile的意义何在？
    private volatile List<String> serverList;
    private ZooKeeper zk = null;

    /**
     * 创建到zk的客户端连接
     * 
     * @throws Exception
     */
    public void getConnect() throws Exception {

        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（应该是我们自己的事件处理逻辑）
                try {
                    //重新更新服务器列表，并且注册了监听
                    getServerList();

                } catch (Exception e) {
                }
            }
        });

    }

    /**
     * 获取服务器信息列表
     * 
     * @throws Exception
     */
    public void getServerList() throws Exception {

        // 获取服务器子节点信息，并且对父节点进行监听
        List<String> children = zk.getChildren(parentNode, true);

        // 先创建一个局部的list来存服务器信息
        List<String> servers = new ArrayList<String>();
        for (String child : children) {
            // child只是子节点的节点名
            byte[] data = zk.getData(parentNode + "/" + child, false, null);
            System.out.println(new String(data));
            servers.add(new String(data));
        }
        // 把servers赋值给成员变量serverList，已提供给各业务线程使用
        serverList = servers;
        
        //打印服务器列表
        System.out.println(serverList);
        
    }

    /**
     * 业务功能
     * 
     * @throws InterruptedException
     */
    public void handleBussiness() throws InterruptedException {
        System.out.println("client start working.....");
        Thread.sleep(Long.MAX_VALUE);
    }
    
    
    
    
    public static void main(String[] args) throws Exception {

        // 获取zk连接
        DistributedClient client = new DistributedClient();
        client.getConnect();
        // 获取servers的子节点信息（并监听），从中获取服务器信息列表
        client.getServerList();

        // 业务线程启动
        client.handleBussiness();
        
    }

}

package cn.itcast.bigdata.zkdist;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;

public class DistributedServer {
    private static final String connectString = "h43:2181,h42:2181";
    private static final int sessionTimeout = 2000;
    private static final String parentNode = "/servers";

    private ZooKeeper zk = null;

    /**
     * 创建到zk的客户端连接
     * 
     * @throws Exception
     */
    public void getConnect() throws Exception {

        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（应该是我们自己的事件处理逻辑）
                System.out.println(event.getType() + "---" + event.getPath());
                try {
                    zk.getChildren("/", true);
                } catch (Exception e) {
                }
            }
        });

    }

    /**
     * 向zk集群注册服务器信息
     * 
     * @param hostname
     * @throws Exception
     */
    public void registerServer(String hostname) throws Exception {
//需要先在zk里面创建 /servers 节点
        String create = zk.create(parentNode + "/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        System.out.println(hostname + "is online.." + create);

    }

    /**
     * 业务功能
     * 
     * @throws InterruptedException
     */
    public void handleBussiness(String hostname) throws InterruptedException {
        System.out.println(hostname + "start working.....");
        Thread.sleep(Long.MAX_VALUE);
    }

    public static void main(String[] args) throws Exception {

        // 获取zk连接
        DistributedServer server = new DistributedServer();
        server.getConnect();

        // 利用zk连接注册服务器信息
        server.registerServer(args[0]);

        // 启动业务功能
        server.handleBussiness(args[0]);

    }

}

也可以在上面的基础上继续实现负载均衡。

打jar 包放在服务器上

java -jar server.jar h42 启动