What else do you want to use ZK for - just leader election? It doesn't
require so much a centralised server (which implies kind of a single point
of failure) as a small amount of fixed infrastructure. If you have a highly
dynamic network - an ad-hoc network like a social net - ZK will likely not
be appropriate. There are leader election algorithms that work better in
totally ad-hoc networks, and other co-ordination models that are better
suited. In particular, you may not want persistence in the sense that later
instances of a consensus algorithm might not need to see the results of
previous ones, removing the need to keep logs synchronised.

However, if you have five or so servers that you can dedicate to
coordination, ZooKeeper should work very well. I'm really curious about your
use case - is there more you can explain?

Henry

On Thu, Jun 25, 2009 at 7:16 PM, Harold Lim <rold...@yahoo.com> wrote:

>
> Hi Gustavo,
>
> Actually, in my case, we have a fully decentralized service. Something like
> where you have users in a social network. Originally, we were thinking of
> using a distributed consensus algorithm (e.g., Paxos) to perform some
> functionalities (e.g., leader election).
>
> Then, I read about ZooKeeper and was thinking of using ZooKeeper for leader
> election instead. However, that means that we're introducing a "central"
> server/service to the architecture.
>
> Currently, I'm just thinking of some of the original functionalities and
> how much of these functionalities I can offload to ZooKeeper, without
> breaking the original privacy/security motivation.
>
>
> -Harold
>
>
>
>
> --- On Thu, 6/25/09, Gustavo Niemeyer <gust...@niemeyer.net> wrote:
>
> > From: Gustavo Niemeyer <gust...@niemeyer.net>
> > Subject: Re: General Question about Zookeeper
> > To: zookeeper-user@hadoop.apache.org
> > Date: Thursday, June 25, 2009, 1:59 PM
> > Hey Harold,
> >
> > > I am interested in a security aspect of zookeeper,
> > where the clients and the servers don't necessarily belong
> > to the same "group". If a client creates a znode in the
> > zookeeper? Can the person, who owns the zookeeper server,
> > simply look at its filesystem and read the data
> > (out-of-band, not using a client, simply browsing the file
> > system of the machine hosting the zookeeper server)?
> >
> > Yes, absolutely.  You could certainly encrypt the data
> > that goes
> > through the ZooKeeper server, but since ZooKeeper is
> > supposed to be
> > doing coordination work, I think that if you don't trust
> > the server,
> > the whole situation might get a bit awkward.  I'm
> > curious about your
> > use case, since I'm pondering about doing something where
> > clients
> > don't necessarily trust other clients or machines in the
> > same network
> > (or even different users in the same machine), thus might
> > require
> > additional tighting up, but if you don't trust the server
> > itself, that
> > may be tricky.  Please note that ZooKeeper isn't meant
> > to be used just
> > as a distributed filesystem for storage, but that's
> > probably not your
> > intention anyway.
> >
> > --
> > Gustavo Niemeyer
> > http://niemeyer.net
> >
>
>
>
>

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