利用zookeeper实现发布订阅模式
zookeeper应用
发布订阅
zk实现的方式是推拉结合,Client想服务端注册自己需要关注的节点,一旦节点的数据发生变更,那么Server会向对应的客户端发送Watcher事件通知,客户端接收到这个消息后,需要主动到服务端获取最新的数据。
目前很多应用使用发布订阅都不是用zk的这种方式,比较典型的纯的推模式和拉模式,这个之前有记录过Notify和MetaQ的比较,不是本篇的重点。本次主要是利用zookeeper来实现以下发布订阅这种功能。
搭建了一个zk环境,手动创建了一个节点/publish,客户端发布者代码如下:
package com.wpr.zk.pulish;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import java.io.IOException;
import java.util.concurrent.CountDownLatch;
/**
* 利用zk来模拟发布订阅模式
* Created by peirong.wpr on 2017/4/5.
*/
public class Publish implements Watcher{
private static CountDownLatch latch = new CountDownLatch(1);
private static Stat stat = new Stat();
private static ZooKeeper zk =null;
private final static Integer SESSION_TIMEOUT = 5000;
public static void main(String[] args) {
try {
String path ="/publish";
zk = new ZooKeeper("192.168.109.130:2181",SESSION_TIMEOUT,new Publish());
latch.await();
System.out.println("zk connection");
byte[] temp = zk.getData(path,true,stat);
System.out.println("init data :pulish node data"+new String(temp));
int i=0;
while(true){
System.out.println( "publish new Data:"+i);
zk.setData(path,String.valueOf(i).getBytes(),-1);
Thread.sleep(5000L);
i++;
}
} catch (InterruptedException e) {
e.printStackTrace();
} catch (KeeperException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public void process(WatchedEvent event) {
if(Event.KeeperState.SyncConnected == event.getState()){
System.out.println("receive watched event:"+event);
System.out.println(event.getState());
latch.countDown();
}
}
}
订阅者代码如下:
package com.wpr.zk.pulish;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import java.io.IOException;
import java.util.concurrent.CountDownLatch;
/**
* Created by peirong.wpr on 2017/4/5.
*/
public class Subscribe implements Watcher {
private static CountDownLatch latch = new CountDownLatch(1);
private static Stat stat = new Stat();
private static ZooKeeper zk =null;
private final static Integer SESSION_TIMEOUT = 5000;
public static void main(String[] args) {
try {
String path ="/publish";
zk = new ZooKeeper("192.168.109.130:2181",SESSION_TIMEOUT,new Subscribe());
latch.await();
System.out.println("zk connection");
byte[] temp = zk.getData(path,true,stat);
System.out.println("init data :pulish node data"+new String(temp));
int i=0;
while(true){
Thread.sleep(Integer.MAX_VALUE);
}
} catch (InterruptedException e) {
e.printStackTrace();
} catch (KeeperException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public void process(WatchedEvent event) {
if(Event.KeeperState.SyncConnected == event.getState()){
if(Event.EventType.None == event.getType() && event.getPath() == null){
latch.countDown();
}else if(event.getType() == Event.EventType.NodeDataChanged){
//Clinet需要去拉取最新的数据信息
try {
byte[] newByte = zk.getData(event.getPath(),true,stat);
System.out.println("path:"+event.getPath()+"\tdata has changed.\t new Data :"+ new String(newByte));
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}