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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: Dynamic addition of server to a running cluster
Date Wed, 06 Jul 2011 16:42:34 GMT
Alex seems to have nominated me to explain the rolling restart.

This is a manual process whereby you restart each server, one at a time with
the new configuration.  Changing configuration to add servers to the cluster
needs a little bit of thought, but in the absence of server failure during
the transition is pretty tame.

There are subtleties possible, but the simplest way to expand from 3 to 5
servers is to simply reconfigure the 3 to consider themselves part of the
larger cluster, configure the 2 new servers and then bounce each old server,
one at a time and then start the two new servers.

On Tue, Jul 5, 2011 at 5:55 PM, Alexander Shraer <shralex@yahoo-inc.com>wrote:

> Hi Paul,
>
> There's currently no automated way toadd/remove servers. This is ZK-107.
> I'm currently implementing this feature, but it will take some time till
> its in. In the meanwhile there is a "rolling restart" method people use,
> that someone else (Ted?) would explain better than me. The procedure you
> describe doesnt work - it doesnt affect the quorums usedinternally  by ZK
> which are determined when a server first starts and also keep in mind that
> servers can reboot and go back to using the old config file when restarted.
>
> Alex
> Sent from mobile
>
> On Jul 5, 2011, at 8:36 PM, "Paul Rimba" <paul.rimba@gmail.com> wrote:
>
> > Hey there,
> >
> > is there any way to dynamically add a new server to a running cluster?
> >
> > i tried searching on google and i found that this issue has not been
> fixed.(
> > https://issues.apache.org/jira/browse/ZOOKEEPER-762)
> >
> >
> > To my understanding, all the servers in a cluster must have the same
> > configuration(zoo.cfg).
> >
> > If a new server wants to join an already running cluster, how does it get
> > the same configuration from the cluster before appending his own
> > server.x=host:port:electionport?
> >
> > and how does every server get the updated configuration? What i did so
> far
> > is to upload it a znode, say /config/zoo.cfg and when there is a
> > change(NodeDatachanged),
> > every server gets the updated version (is this the right approach?)
> >
> > thanks in advance
>

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