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From Christian Ziech <christian.zi...@nokia.com>
Subject Zookeeper on short lived VMs and ZOOKEEPER-107
Date Wed, 14 Mar 2012 16:04:17 GMT
LEt me describe our upcoming use case in a few words: We are planning to 
use zookeeper in a cloud were typically nodes come and go unpredictably. 
We could ensure that we always have a more or less fixed quorum of 
zookeeper servers with a fixed set of host names. However the IPs 
associated with the host names would change every time a new server 
comes up. I browsed the code a little and it seems right now that the 
only problem is that the zookeeper server is remembering the resolved 
InetSocketAddress in its QuorumPeer hash map.

I saw that possibly ZOOKEEPER-107 would also solve that problem but 
possibly in a more generic way than actually needed (perhaps here I 
underestimate the impact of joining as a server with an empty data 
directory to replace a server that previously had one).

Given that - from looking at ZOOKEEPER-107 - it seems that it will still 
take some time for the proposed fix to make it into a release, would it 
make sense to invest time into a smaller work fix just for this 
"replacing a dropped server without rolling restarts" use case? Would 
there be a chance that a fix for this makes it into the 3.4.x branch?

Are there perhaps other ways to get this use case supported without the 
need for doing rolling restarts whenever we need to replace one of the 
zookeeper servers?

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