shell
[root@hadoop102 zookeeper-3.4.10]# /opt/module/zookeeper-3.4.10/bin/zkServer.sh start
[root@hadoop103 zookeeper-3.4.10]# /opt/module/zookeeper-3.4.10/bin/zkServer.sh start
[root@hadoop104 zookeeper-3.4.10]# /opt/module/zookeeper-3.4.10/bin/zkServer.sh start
shell
/opt/module/zookeeper-3.4.10/bin/zkServer.sh status
shell
/opt/module/zookeeper-3.4.10/bin/zkServer.sh stop
命令基本语法 | 功能描述 |
---|---|
help | 显示所有操作命令 |
ls path [watch] | 使用 ls 命令来查看当前znode中所包含的内容 |
ls2 path [watch] | 查看当前节点数据并能看到更新次数等数据 |
create | 普通创建-s 含有序列-e 临时(重启或者超时消失) |
get path [watch] | 获得节点的值 |
set | 设置节点的具体值 |
stat | 查看节点状态 |
delete | 删除节点 |
rmr | 递归删除节点 |
xml
<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>
java
package cn.buildworld.zookeeper;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.util.List;
/**
* @author MiChong
* @date 2020-06-07 14:13
*/
public class ZkClient {
private ZooKeeper zkClient;
private static final String CONNECT_URL = "192.168.162.102:2181,192.168.162.103:2181,192.168.162.104:2181";
private static final int SESSION_TIME_OUT = 2000;
/**
** 创建客户端
**/
@Before
public void before() throws IOException {
zkClient = new ZooKeeper(CONNECT_URL, SESSION_TIME_OUT, (e) -> {
System.out.println("命令执行完成回调!");
});
}
/**
* 获取目录
* @throws KeeperException
* @throws InterruptedException
*/
@Test
public void ls() throws KeeperException, InterruptedException {
List<String> children = zkClient.getChildren("/", event -> {
System.out.println("目录获取完成!");
});
for (String path : children) {
System.out.println(path);
}
Thread.sleep(Long.MAX_VALUE);
}
/**
* 创建目录
* @throws KeeperException
* @throws InterruptedException
*/
@Test
public void create() throws KeeperException, InterruptedException {
String path = zkClient.create("/Idea",
"234567".getBytes(),
ZooDefs.Ids.CREATOR_ALL_ACL,
CreateMode.EPHEMERAL);
System.out.println("创建的路径:"+path);
}
/**
* 获取指定目录下面的数据
* @throws KeeperException
* @throws InterruptedException
*/
@Test
public void get() throws KeeperException, InterruptedException {
byte[] data = zkClient.getData("/test", true, new Stat());
String s = new String(data);
System.out.println(s);
}
/**
* 更新数据
* @throws KeeperException
* @throws InterruptedException
*/
@Test
public void set() throws KeeperException, InterruptedException {
Stat stat = zkClient.setData("/test", "hello world".getBytes(), 0);
byte[] data = zkClient.getData("/test", true, stat);
String s = new String(data);
System.out.println("更新之后的数据:"+s);
}
/**
* 获取节点状态
* @throws KeeperException
* @throws InterruptedException
*/
@Test
public void stat() throws KeeperException, InterruptedException {
Stat exists = zkClient.exists("/test", false);
if (exists == null){
System.out.println("节点不存在!");
}else {
System.out.println(exists.getDataLength());
}
}
/**
* 删除
* @throws KeeperException
* @throws InterruptedException
*/
@Test
public void delete() throws KeeperException, InterruptedException {
Stat exists = zkClient.exists("/test", false);
if (exists != null){
zkClient.delete("/test",exists.getVersion());
}else {
System.out.println("节点不存在!");
}
}
}
每次修改ZooKeeper状态都会收到一个zxid形式的时间戳,也就是ZooKeeper事务ID。 事务ID是ZooKeeper中所有修改总的次序。每个修改都有唯一的zxid,如果zxid1小于zxid2,那么zxid1在zxid2之前发生。
选举流程
(1)服务器1启动,发起一次选举。服务器1投自己一票。此时服务器1票数一票,不够半数以上(3票),选举无法完成,服务器1状态保持为LOOKING;
(2)服务器2启动,再发起一次选举。服务器1和2分别投自己一票并交换选票信息:此时服务器1发现服务器2的ID比自己目前投票推举的(服务器1)大,更改选票为推举服务器2。此时服务器1票数0票,服务器2票数2票,没有半数以上结果,选举无法完成,服务器1,2状态保持LOOKING
(3)服务器3启动,发起一次选举。此时服务器1和2都会更改选票为服务器3。此次投票结果:服务器1为0票,服务器2为0票,服务器3为3票。此时服务器3的票数已经超过半数,服务器3当选Leader。服务器1,2更改状态为FOLLOWING,服务器3更改状态为LEADING;
(4)服务器4启动,发起一次选举。此时服务器1,2,3已经不是LOOKING状态,不会更改选票信息。交换选票信息结果:服务器3为3票,服务器4为1票。此时服务器4服从多数,更改选票信息为服务器3,并更改状态为FOLLOWING;
(5)服务器5启动,同4一样当小弟。