ZooKeeper Connection Loss 异常

原因:

一般是由于连接还未完成就执行zookeeper的get/create/exsit操作引起的.

解决方法:

利用"CountDownLatch 类 + zookeeper的watcher + zookeeper的getStat" 实现连接完成后再调用.

可防止此错误发生.

示例类如下(为一配置获取类):

[java] view plaincopy

1. import java.util.concurrent.CountDownLatch;  
2.   
3.   
4. import org.apache.zookeeper.WatchedEvent;  
5. import org.apache.zookeeper.Watcher;  
6. import org.apache.zookeeper.Watcher.Event.KeeperState;  
7. import org.apache.zookeeper.ZooKeeper;  
8. import org.apache.zookeeper.ZooKeeper.States;  
9. import org.apache.zookeeper.data.Stat;  
10. public class Conf{  
11.     public static void waitUntilConnected(ZooKeeper zooKeeper, CountDownLatch connectedLatch) {  
12.         if (States.CONNECTING == zooKeeper.getState()) {  
13.             try {  
14.                 connectedLatch.await();  
15.             } catch (InterruptedException e) {  
16.                 throw new IllegalStateException(e);  
17.             }  
18.         }  
19.     }  
20.    
21.     static class ConnectedWatcher implements Watcher {  
22.    
23.         private CountDownLatch connectedLatch;  
24.    
25.         ConnectedWatcher(CountDownLatch connectedLatch) {  
26.             this.connectedLatch = connectedLatch;  
27.         }  
28.    
29.         @Override  
30.         public void process(WatchedEvent event) {  
31.            if (event.getState() == KeeperState.SyncConnected) {  
32.                connectedLatch.countDown();  
33.            }  
34.         }  
35.     }  
36.     static public Conf Instance(){  
37.         if(static_ == null){  
38.             static_ = new Conf();  
39.         }  
40.         return static_;  
41.     }  
42.     public boolean Init(String hostports, int times){  
43.         try{  
44.             CountDownLatch connectedLatch = new CountDownLatch(1);  
45.             Watcher watcher = new ConnectedWatcher(connectedLatch);  
46.             zk_ = new ZooKeeper(hostports, times, watcher);  
47.             waitUntilConnected(zk_, connectedLatch);  
48.         }  
49.         catch(Exception e){  
50.             System.out.println(e);  
51.             return false;  
52.         }  
53.         return true;  
54.     }  
55.     public String Get(String keys){  
56.         String re = "";  
57.         String ppath = "/zookeeper";  
58.         int oldpos = -1;  
59.         int pos = 0;  
60.         while(true){  
61.             pos = keys.indexOf(".", oldpos + 1);  
62.             if(pos < 0){  
63.                 ppath += "/";  
64.                 String str = keys.substring(oldpos + 1);  
65.                 ppath += str;  
66.                 break;  
67.             }  
68.             ppath += "/";  
69.             String str = keys.substring(oldpos + 1,  pos);  
70.             ppath += str;  
71.             oldpos = pos;  
72.         }  
73.         Stat stat = new Stat();  
74.         try{  
75.             byte[] b = zk_.getData(ppath, false, stat);    //获取节点的信息及存储的数据  
76.             re = new String(b);  
77.         }  
78.         catch(Exception e){  
79.             System.out.println(e);  
80.         }  
81.         return re;  
82.     }  
83.     private Conf(){  
84.           
85.     }  
86.     private ZooKeeper zk_;  
87.     static private Conf static_;  
88.     public static void main(String args[]){  
89.         String hostports = "192.168.1.88:2181,192.168.1.88:2182,192.168.1.88:2183";  
90.           
91.         Conf.Instance().Init(hostports, 1000);  
92.           
93.         String str = Conf.Instance().Get("conf.logicpoint.subscriberserverip");  
94.         str = Conf.Instance().Get("conf.logicpoint.subscriberserverport");  
95.         System.out.println(str);  
96.         while(true){  
97.             try{Thread.sleep(100);}  
98.             catch(Exception e){  
99.                   
100.             }  
101.         }  
102.           
103.     }  
104. }