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:[EMAIL PROTECTED] Sent: Friday, September 12, 2008 2:49 AM To: firstname.lastname@example.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