3.1 客户端命令行操作
1)help : 显示所有的操作指令;
2)ls path : 使用ls命令来查看当前znode的子节点
-w :监听子节点变化(只能监听一次)
3) 查看当前目录下的详细信息:
ls -s path / ls2 path / stat path
4) create 创建节点 (默认创建的是:持久性无顺序号的节点)
-s 含顺序号
-e 临时的
5) get path : 获得节点的值
-w 监听节点内容变化
6) set path :设置节点具体的值
8) delete : 删除节点
9) deleteall:递归删除节点。
3.2 API应用
- 创建Maevn Modle
- 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>3.5.7</version>
</dependency>
</dependencies>
- 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("/hanxiao", "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zonde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");
}
3.3 监听服务器节点动态上下线案例
服务器端向Zookeeper注册代码
package com.hanxiao.zkcase;
package com.hanxiao.zookeeper;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import java.io.IOException;
/**
* 当服务器上线后, 将当前服务器对应的信息写到zk中
*/
public class Server {
private String connectionString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
private int sessionTimeOut = 10000;
private ZooKeeper zkClient = null ;
private String parentNode = "/servers";
public static void main(String[] args) throws Exception {
Server server = new Server ();
//1. 初始化zk客户端对象
server.init();
//2. 判断zk中存储服务器信息的Znode是否存在
server.parentNodeExists();
//3. 将服务器的信息写入到zk中
server.writeServer(args);
//4. 保持线程不结束
Thread.sleep(Long.MAX_VALUE);
}
/**
* args中包含两个数据:
* 1. server的名字
* 2. server的信息
* @param args
*/
private void writeServer(String [] args) throws KeeperException, InterruptedException {
String s =
zkClient.create(parentNode + "/" + args[0], args[1].getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
System.out.println("*********** "+ s +"is on line ************");
}
//2. 判断zk中存储服务器信息的Znode是否存在
private void parentNodeExists() throws KeeperException, InterruptedException {
Stat stat = zkClient.exists(parentNode, false);
if(stat == null){
//创建节点
zkClient.create(parentNode,"servers".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
}
}
//1. 初始化zk客户端对象
private void init() throws IOException {
zkClient = new ZooKeeper(connectionString, sessionTimeOut, new Watcher() {
@Override
public void process(WatchedEvent event) {
}
});
}
}
客户端代码
package com.hanxiao.zkcase;
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();
}
}