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From "Benjamin Reed" <br...@yahoo-inc.com>
Subject RE: Re: ephemerals handling after restart
Date Thu, 18 Sep 2008 12:00:28 GMT
Yes

Ben


 -----Original Message-----
From: 	Johannes Zillmann [mailto:jz@101tec.com]
Sent:	Thursday, September 18, 2008 02:22 AM Pacific Standard Time
To:	zookeeper-user@hadoop.apache.org
Subject:	Re: ephemerals handling after restart

Hi Ben,

thanks for your answer!
Is the session recoverable in case the zk server was restarted in  
meantime ?

Johannes

On Sep 12, 2008, at 3:52 PM, Benjamin Reed wrote:

> If a application does not close the ZooKeeper session before shutting
> down, ZooKeeper will not cleanup the session until it times out. So  
> when
> an application crashes and restarts, ZooKeeper doesn't know if the
> client is a restart of an old client or a new client.
>
> There is a way to alleviate this problem: you can actually maintain a
> session across client application restarts. If you save off the  
> session
> id and password, when you restart you can try to reconnect to the
> session using the ZooKeeper constructor that takes the old session id
> and password. If the reconnect is successful you can then close the
> session and get everything to clean up immediately. (Or you could keep
> using the recovered session if you want to.)
>
> ben
>
> -----Original Message-----
> From: Johannes Zillmann [mailto:jz@101tec.com]
> Sent: Friday, September 12, 2008 2:49 AM
> To: zookeeper-user@hadoop.apache.org
> Subject: ephemerals handling after restart
>
> Hi all,
>
> i have a question regarding ephemerals and it behavior on client  
> crash/
> restart.
> We've a master/node cluster similar to a hadoop hdfs cluster but using
> zk for management.
> The nodes creates an ephemeral to announce there existence to the
> master.
>
> Now what i recognized is that after stopping the whole cluster and
> starting only the master again, still some ephemeral nodes may exists
> for some seconds.
> That leads me to following questions.
> What is if a node starts up again. Do it have to clean up it "old"
> ephemeral node, or can it somehow acquire the old one ?
>
> Just trying to find a best way how to deal with this, since on regular
> restart of the cluster i often recognize something like this
> master : node1, node2 connected
> master : node2 disconnected
> master : node2 connected again
>
> Thanks for any help
> Johannes
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 101tec GmbH
> Halle (Saale), Saxony-Anhalt, Germany
> http://www.101tec.com
>
>

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
101tec GmbH
Halle (Saale), Saxony-Anhalt, Germany
http://www.101tec.com


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