It looks like you are losing connectivity btw your client and server. You'd need to provide some basic information for us to do any debugging - for example what version of server/client are you using?

The first "connection loss" exception is probably due to the fact that you got disconnected while a request (getdata) was in progress. However it's not totally clear to me as you don't have date/time in your log, so hard for me to have context.

I suspect the second error is due to session expiration, either that or you are exceeding the "maxclientcnxns" (10 by default) from a single host. There's isn't enough log detail for me to be sure.

***Could it be that you are creating a ZK client connection for each operation of your "web interface"? (or maybe not closing the connection in all cases afterward?) If this is they case you are more than likely hitting the "maxclientcnxns" limit, try grepping the server logs (all of them on all servers) for "Too many connections from" and see if that shows up at all.

Try using the "4 letter words" against your servers to see what your connection status looks like - in particular the "stat" and "dump" commands. Hopefully you are using this for monitoring, if so you might be able to look back at historical information on this.


Goteti Bhanu wrote:

         We are having issues with our web interface (WI) to zookeeper. We 
deployed a java app (WI), in tomcat, which shows a (mostly read-only) UI for 
the zk tree, in our cluster. The app had been deployed quite some time ago. 
However, recently, it is going down many times, in the recent past, showing 
these errors in the catalina.out. These errors are coming continuously in the 
catalina.out, while the website is down.

[INFO] SyncZKTreeWatcher - [registerWatches] About to register watch for 
recursive: false
[INFO] SyncZKTreeWatcher - Path: null, type: None, state: Disconnected
[INFO] SyncZKTreeWatcher - Path: null, type: None, state: SyncConnected
[WARN] SyncZKTreeWatcher - [run] Exception while handling event WatchedEvent: Znode 
change. Path: /llf/version-1.0/serverNodes/llf-server/nodes/b3091258:8085/connected 
Type: NodeChildrenChanged 
<org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = 
KeeperErrorCode = ConnectionLoss
        at org.apache.zookeeper.KeeperException.create(
        at org.apache.zookeeper.ZooKeeper.getData(
        at org.apache.zookeeper.ZooKeeper.getData(

        In another log, we are getting the following errors continuously.

<AlertReceiver.log> Transport endpoint is not connected
        at Method)
        at org.apache.zookeeper.ClientCnxn$
2010 03 16 09:49:55,645   org.apache.zookeeper.ClientCnxn ZK Event 
Handler-SendThread Attempting connection to server
2010 03 16 09:49:55,646   org.apache.zookeeper.ClientCnxn ZK Event 
Handler-SendThread Priming connection to 
java.nio.channels.SocketChannel[connected local=/]
2010 03 16 09:49:55,739   org.apache.zookeeper.ClientCnxn ZK Event 
Handler-SendThread Server connection successful
2010 03 16 09:49:55,775   org.apache.zookeeper.ClientCnxn ZK Event Handler-SendThread 
Exception closing session 0xe727001201aa32ab to<> Read error rc = -1 java.nio.DirectByteBuffer[pos=0 lim=4 
        at org.apache.zookeeper.ClientCnxn$SendThread.doIO(
        at org.apache.zookeeper.ClientCnxn$
2010 03 16 09:49:55,775   org.apache.zookeeper.ClientCnxn ZK Event 
Handler-SendThread Ignoring exception during shutdown input

        What do these errors indicate? Always, restarting tomcat helps. But 
since the problem is occurring many times, we want to understand why is this 
happening? Is there a known ZK issue which could cause such behavior?


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