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From Dave Wright <wrig...@gmail.com>
Subject Dynamic adding/removing ZK servers on client
Date Mon, 03 May 2010 14:03:56 GMT
I've got a situation where I essentially need dynamic cluster
membership, which has been talked about in ZOOKEEPER-107 but doesn't
look like it's going to happen any time soon.

For now, I'm planning on working around this by having a simple
coordinator service on the server nodes that will re-write the configs
and bounce the servers when membership changes. Clients will may get
an error or two and need to reconnect, but that should be handled by
the normal error logic.

On the client side, I'd really like to dynamically update the server
list w/o having to re-create the entire Zookeeper object. Looking at
the code, it seems like it would be pretty trivial to add
"RemoveServer()/AddServer()" functions for Zookeeper that calls down
to ClientCnxn, where they are just maintained in a list. Of course if
the server being removed is the one currently connected, we'd need to
disconnect, but a simple call to disconnect() seems like it would
resolve that and trigger the automatic re-connection logic.

Does anyone see an issue with that approach?
Were I to create the patch, do you think it would be interesting
enough to merge? It seems like that functionality will eventually be
needed for whatever full dynamic server support is eventually

-Dave Wright

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