Zookeeper04-实战

NiuMT 2020-07-03 20:58:30

Hadoop

API应用

创建一个Maven工程

添加pom文件

<dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.8.2</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.zookeeper/zookeeper -->
        <dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.4.10</version>
        </dependency>
</dependencies>

添加log4j.properties文件到项目根目录

需要在项目的src/main/resources目录下，新建一个文件，命名为“log4j.properties”，在文件中填入。

log4j.rootLogger=INFO, stdout  
log4j.appender.stdout=org.apache.log4j.ConsoleAppender  
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout  
log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n  
log4j.appender.logfile=org.apache.log4j.FileAppender  
log4j.appender.logfile.File=target/spring.log  
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout  
log4j.appender.logfile.layout.ConversionPattern=%d %p [%c] - %m%n

创建ZooKeeper客户端

    private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private static int sessionTimeout = 2000;
    private 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（用户的业务逻辑）
                System.out.println(event.getType() + "--" + event.getPath());

                // 再次启动监听
                try {
                    zkClient.getChildren("/", true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

创建子节点

// 创建子节点
@Test
public void create() throws Exception {

        // 参数1：要创建的节点的路径； 参数2：节点数据 ； 参数3：节点权限 ；参数4：节点的类型
        String nodeCreated = zkClient.create("/atguigu", "jinlian".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
}

获取子节点并监听节点变化

// 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);
        }
        // 延时阻塞
        Thread.sleep(Long.MAX_VALUE);
}

判断Znode是否存在

// 判断znode是否存在
@Test
public void exist() throws Exception {
    Stat stat = zkClient.exists("/eclipse", false);
    System.out.println(stat == null ? "not exist" : "exist");
}

监听服务器节点动态上下线案例

某分布式系统中，主节点可以有多台，可以动态上下线，任意一台客户端都能实时感知到主节点服务器的上下线。

服务器端向Zookeeper注册代码

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

public class DistributeServer {

    private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private static int sessionTimeout = 2000;
    private ZooKeeper zk = null;
    private String parentNode = "/servers";

    // 创建到zk的客户端连接
    public void getConnect() throws IOException{
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent event) {

            }
        });
    }

    // 注册服务器
    public void registServer(String hostname) throws Exception{
        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
    public void business(String hostname) throws Exception{
        System.out.println(hostname+" is working ...");
        Thread.sleep(Long.MAX_VALUE);
    }

    public static void main(String[] args) throws Exception {
        // 1获取zk连接
        DistributeServer server = new DistributeServer();
        server.getConnect();
        // 2 利用zk连接注册服务器信息
        server.registServer(args[0]);
        // 3 启动业务功能
        server.business(args[0]);
    }
}

客户端代码

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;

public class DistributeClient {

    private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private static int sessionTimeout = 2000;
    private ZooKeeper zk = null;
    private String parentNode = "/servers";

    // 创建到zk的客户端连接
    public void getConnect() throws IOException {
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                // 再次启动监听
                try {
                    getServerList();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    // 获取服务器列表信息
    public void getServerList() throws Exception {
        // 1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);
        // 2存储服务器信息列表
        ArrayList<String> servers = new ArrayList<>();
        // 3遍历所有节点，获取节点中的主机名称信息
        for (String child : children) {
            byte[] data = zk.getData(parentNode + "/" + child, false, null);
            servers.add(new String(data));
        }
        // 4打印服务器列表信息
        System.out.println(servers);
    }

    // 业务功能
    public void business() throws Exception{
        System.out.println("client is working ...");
        Thread.sleep(Long.MAX_VALUE);
    }

    public static void main(String[] args) throws Exception {
        // 1获取zk连接
        DistributeClient client = new DistributeClient();
        client.getConnect();
        // 2获取servers的子节点信息，从中获取服务器信息列表
        client.getServerList();
        // 3业务进程启动
        client.business();
    }
}

企业面试真题

请简述ZooKeeper的选举机制
ZooKeeper的监听原理是什么？
ZooKeeper的部署方式有哪几种？集群中的角色有哪些？集群最少需要几台机器？

（1）部署方式单机模式、集群模式

（2）角色：Leader和Follower

（3）集群最少需要机器数：3
ZooKeeper的常用命令

ls create get delete set…

Zookeeper03-Shell操作

Hive01-概述