010 Zookeeper

Zookeeper从设计模式角度来理解，是一个基于观察者模式设计的分布式服务管理框架，它负责存储和管理大家都关心的数据，然后接受观察者的注册，一旦这些数据的状态发生了变化，Zookeeper就负责通知已经在Zookeeper上注册的那些观察者做出相应的反应.

• 面试题：4个zookeeper的应用场景，你知道几个？
• Zookeeper及其应用场景
• ZooKeeper 的应用场景

# 集群启动：hadoop102、hadoop103、hadoop104
[atguigu@hadoop102 zookeeper-3.5.7]$ zkServer.sh start
# 查看状态：hadoop102、hadoop103、hadoop104
[atguigu@hadoop102 zookeeper-3.5.7]$ bin/zkServer.sh status
# 启动客户端
[atguigu@hadoop103 zookeeper-3.5.7]$ bin/zkCli.sh
# 查看命令
[zk: localhost:2181(CONNECTED) 2] help
ZooKeeper -server host:port cmd args
	addauth scheme auth
	close 
	config [-c] [-w] [-s]
	connect host:port
	create [-s] [-e] [-c] [-t ttl] path [data] [acl]
	delete [-v version] path
	deleteall path
	delquota [-n|-b] path
	get [-s] [-w] path
	getAcl [-s] path
	history 
	listquota path
	ls [-s] [-w] [-R] path
	ls2 path [watch]
	printwatches on|off
	quit 
	reconfig [-s] [-v version] [[-file path] | [-members serverID=host:port1:port2;port3[,...]*]] | [-add serverId=host:port1:port2;port3[,...]]* [-remove serverId[,...]*]
	redo cmdno
	removewatches path [-c|-d|-a] [-l]
	rmr path
	set [-s] [-v version] path data
	setAcl [-s] [-v version] [-R] path acl
	setquota -n|-b val path
	stat [-w] path
	sync path
Command not found: Command not found help

添加pom文件

		
			junit
			junit
			RELEASE
		
		
			org.apache.logging.log4j
			log4j-core
			2.8.2
		
		
			org.apache.zookeeper
			zookeeper
			3.5.7
		

log4j.properties

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

JAVA实例程序

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

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


public class TestZkClient {

    private ZooKeeper zk;
    
    @Before
    public void initZkClient() throws IOException {
        // 连接ZK集群的地址
        String connectionStr = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
        // 超时时间
        int sessionTimeOut = 10000;
        zk = new ZooKeeper(connectionStr, sessionTimeOut, new Watcher() {
            public void process(WatchedEvent event) {
//                System.out.println("监听到有变化");
            }
        });
    }

    @After
    public void closeZk() throws InterruptedException {
        zk.close();
    }
    
	@Test
    public void ls() throws IOException, KeeperException, InterruptedException {
        //用客户端对象做各种操作
        List children = zk.getChildren("/", false);
        System.out.println(children);
    }

JAVA运行输出

2021-12-30 22:45:25,769 INFO [org.apache.zookeeper.ClientCnxn] - Opening socket connection to server hadoop103/192.168.2.35:2181. Will not attempt to authenticate using SASL (unknown error)
2021-12-30 22:45:25,772 INFO [org.apache.zookeeper.ClientCnxn] - Socket connection established, initiating session, client: /192.168.2.9:56683, server: hadoop103/192.168.2.35:2181
2021-12-30 22:45:25,810 INFO [org.apache.zookeeper.ClientCnxn] - Session establishment complete on server hadoop103/192.168.2.35:2181, sessionid = 0x300071438870000, negotiated timeout = 10000
[zookeeper, sanguo]
2021-12-30 22:45:25,948 INFO [org.apache.zookeeper.ZooKeeper] - Session: 0x300071438870000 closed
2021-12-30 22:45:25,948 INFO [org.apache.zookeeper.ClientCnxn] - EventThread shut down for session: 0x300071438870000