zookeeper 分布式容灾代码示例

bestu

废话少说直接上代码！

import java.net.InetAddress;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
public class ClusterTest {
static ZooKeeper zk = null;
static Map<String, Watcher> myWatchMap = new HashMap<String, Watcher>();
static String ip = null;
public static void init() throws InterruptedException {
for(int i = 1; i < 6; i++){
final int k = i;
Thread t = new Thread(new Runnable() {
@Override
public void run() {
// 创建一个与服务器的连接
try {
ZooKeeper zk = new ZooKeeper(
"localhost:2181,localhost:2182", 1000, null);
String path = ip+k;
if(zk.exists(path, false) == null){
zk.create(path, "testRootData".getBytes(), Ids.OPEN_ACL_UNSAFE,
CreateMode.EPHEMERAL);
}
Thread.sleep(1000);
zk.close();
} catch (Exception e) {
//e.printStackTrace();
}
}
});
t.start();
t.setName("RISHENG-THREAD-"+i);
}
}
/**
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
InetAddress addr = InetAddress.getLocalHost();
ip="/zookeeper/"+addr.getHostAddress();
// 创建一个与服务器的连接
zk = new ZooKeeper("localhost:2181,localhost:2182",
1000, null);
List<String> nodeList = zk.getChildren("/zookeeper", false);
System.err.println(nodeList);
init();
regWatch();
while(true){
Thread.sleep(1000);
init();
regWatch();
}
}
public static void regWatch() throws KeeperException, InterruptedException{
for(int i = 1; i < 6; i++){
String path = ip+i;
Watcher watch = null;
if(!myWatchMap.containsKey(path)){
watch = new MyWatch(zk, path);
myWatchMap.put(path, watch);
}
zk.exists(path, watch);
}
}
}
class MyWatch implements Watcher{
private ZooKeeper zk = null;
private String path = null;
public MyWatch(ZooKeeper zk, String path){
this.zk = zk;
this.path = path;
}
@Override
public void process(WatchedEvent event) {
if(EventType.NodeDeleted.equals(event.getType())){
System.err.println(event.getPath()+"====服务关闭===="+path);
} else if(EventType.NodeCreated.equals(event.getType())){
System.out.println(event.getPath()+"====服务开启===="+path);
}
try {  
zk.exists(event.getPath(), this);  
} catch (KeeperException e) {  
} catch (InterruptedException e) {  
}  
}
}

另外有几点需要关注：
1、如果重复的new新的Watcher会导致订阅端重复收到通知；
2、zk的Watcher是一次性消费，用完后记得重新注册；
3、zk不保证通知关系始终简历，所以需要轮询注册Watcher