zookeeper-客户端命令和API应用
客户端命令行操作
| 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 |
启动客户端
bin/zkCli.shAPI应用
Eclipse环境搭建
1．创建一个Maven工程
2．添加pom文件
junit
junit
RELEASE
org.apache.logging.log4j
log4j-core
2.8.2
org.apache.zookeeper
zookeeper
3.4.10
3．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 String connectString = "hadoop101:2181,hadoop102:2181,hadoop103:2181";
private int sessionTimeout = 2000;
private ZooKeeper zkClient;
//创建ZooKeeper客户端
@Before
public void init() throws IOException {
zkClient = new ZooKeeper(connectString, sessionTimeout ,new Watcher() {
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
//1 创建节点
@Test
public void createNode() throws KeeperException, InterruptedException {
zkClient.create("/liun", "1221".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
}获取子节点并监听节点变化
//2 获取子节点 并监控数据的变化
@Test
public void getDataAndWatch() throws KeeperException, InterruptedException {
List 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
// 3 判断节点是否存在
@Test
public void exist() throws KeeperException, InterruptedException {
Stat stat = zkClient.exists("/liun", false);
System.out.println(stat==null? "not exist":"exsit");
}监听服务器节点动态上下线案例
需求
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。
先在集群上创建/servers节点
create /servers "servers"（1）服务器端向Zookeeper注册代码
package com.liu.zookeeper;
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.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
public class DistributeServer {
private String connectString = "hadoop101:2181,hadoop102:2181,hadoop103:2181";
private int sessionTimeout = 2000;
private ZooKeeper zkClient;
public static void main(String[] args) throws Exception {
DistributeServer server = new DistributeServer();
// 1 连接zookeeper集群
server.getConnect();
// 2 注册节点
server.regist(args[0]);
// 3 业务逻辑处理
server.business(args[0]);
}
//业务功能
private void business(String hostname) throws Exception {
System.out.println(hostname +"is working");
Thread.sleep(Long.MAX_VALUE);
}
// 注册服务器
private void regist(String hostname) throws KeeperException, InterruptedException {
String path = zkClient.create("/servers/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
System.out.println(hostname + "is online");
}
// 创建到zk的客户端连接
private void getConnect() throws IOException{
zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
public void process(WatchedEvent event) {
// TODO Auto-generated method stub
}
});
}
}
（2）客户端代码
package com.liu.zookeeper;
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;
public class DistributeClient {
private String connectString = "hadoop101:2181,hadoop102:2181,hadoop103:2181";
private int sessionTimeout = 2000;
private ZooKeeper zkClient;
public static void main(String[] args) throws Exception {
DistributeClient client = new DistributeClient();
// 1获取zookeeper集群连接
client.getConnect();
// 2注册监听
client.getChildren();
// 3业务逻辑处理
client.business();
}
private void business() throws Exception {
Thread.sleep(Long.MAX_VALUE);
}
private void getChildren() throws KeeperException, InterruptedException {
List children = zkClient.getChildren("/servers", true);
//存储服务器节点主机名称集合
ArrayList hosts = new ArrayList<>();
for (String child : children) {
byte[] data = zkClient.getData("/servers"+child, false, null);
hosts.add(new String(data));
}
// 将所有在线主机名称打印到控制台
System.out.println(hosts);
}
private void getConnect() throws IOException {
zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
public void process(WatchedEvent event) {
try {
getChildren();
} catch (KeeperException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
}