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From Patrick Hunt <ph...@apache.org>
Subject Re: Client reconnection after a connection loss
Date Wed, 21 Apr 2010 16:13:52 GMT
Hi Julien,

take a look at the FAQ for some background:
http://wiki.apache.org/hadoop/ZooKeeper/FAQ#A3

Basically when your client connects to the server it provides a 
"timeout" value. If the server doesn't hear from your client within this 
timeout period (we do heartbeating for you in a background thread, you 
don't have to worry about this) then it will expire the session.
http://hadoop.apache.org/zookeeper/docs/current/zookeeperProgrammers.html#ch_zkSessions

You have a watcher for the session - it will be notified both on 
disconnect but also when/if the session is expired. An expired session 
is invalid, if this happens you have to create a new session. This is 
different from a disconnect notification, where you just wait for the 
client library to reconnect you to the cluster (say you lose 
connectivity to the server)

Patrick

On 04/21/2010 01:44 AM, Julien Vey wrote:
> Hi all,
>
> I'm currently working with ZooKeeper in CXF D-OSGI and i'm facing a
> problem that would require your help.
>
> When a client is connected to the ZooKeeper server, and the connection
> is lost, it throws a ConnectionLossException.
> The problem is when the connection is back, the client doesn't reconnect
> itself. I can see the following trace on the server
>
> 2010-04-20 17:44:21,526 - INFO [NIOServerCxn.Factory:>
> 0.0.0.0/0.0.0.0:2181:NIOServerCnxn$Factory@251] - Accepted socket
> connection from /129.183.128.230:60471
> 2010-04-20 17:44:21,526 - INFO [NIOServerCxn.Factory:
> 0.0.0.0/0.0.0.0:2181:NIOServerCnxn@742] - Client attempting to renew
> session0x1281ba54e900005 at /129.183.128.230:60471
> 2010-04-20 17:44:21,527 - INFO [NIOServerCxn.Factory:
> 0.0.0.0/0.0.0.0:2181:NIOServerCnxn@1424] - Invalid session
> 0x1281ba54e900005 for client /129.183.128.230:60471, probably expired
> 2010-04-20 17:44:21,527 - INFO [NIOServerCxn.Factory:
> 0.0.0.0/0.0.0.0:2181:NIOServerCnxn@1286] - Closed socket connection for
> client /129.183.128.230:60471 which had sessionid 0x1281ba54e900005
>
> The client tries to reconnect with an expired session id.
> Is it possible to configure zookeeper in order that it accepts this
> connection by recreating a new session, or maybe something else that
> would make the reconnection works ?
>
> Thanks in advance for your help
>
> Julien.
>
>
>

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