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From Jared Cantwell <jared.cantw...@gmail.com>
Subject Re: Growing a cluster
Date Thu, 05 May 2011 16:36:16 GMT
Thats Patrick, this is roughly the procedure we have are testing.

In your procedure, can (4) and (5) be performed simultaneously?

Also, am I correct in thinking that going from 1 to 3 server could be
dangerous for this reason:
1. start server 1 in standalone mode and write some data to it
2. follow you procedure with 3 servers
3. say during leader election, servers 2 and 3 form the quorum first and
elect server 2 as the leader.
4. server 2 believes the last txn to be 0, since it is a fresh cluster
5. now server 1 joins the quorum and knows about txn 100, but the other 2
servers do not, uh oh

Is this a real problem, or is there something preventing this case?  It
seems like you can only grow a cluster such that at least on member of the
old quorum MUST be present in the new quorum.  Is this correct?

~Jared

2011/5/5 Patrick Hunt <phunt@apache.org>

> Hi Jared, you can go from 1 to 2+ nodes just fine:
>
> 1) change the configuration of server 1 from standalone to quorum
> based (be sure to list the new members of the ensemble)
> 2) add a myid file for server 1
> 3) setup new servers 2+
> 4) restart server 1
> 5) start servers 2+
>
> At this point the quorum should just come up. I just tried this
> example and it worked fine for me going from 1 to 3 (the data I
> created in standalone was available once I started the ensemble).
>
> Regards,
>
> Patrick
>
> 2011/5/5 Jared Cantwell <jared.cantwell@gmail.com>:
> > Great information guys-- this helps me understand what needs done when
> > expanding from 2 nodes to X nodes.
> >
> > Does anyone have insight on going from 1 node to 3 nodes?
> >
> > ~Jared
> >
> > 2011/5/5 Chang Song <tru64ufs@me.com>
> >
> >>
> >> We are in a bit similar situation.
> >>
> >> 3 node -> 5 node ensemble.
> >>
> >> The only way to do this is the following.
> >>
> >> Assumption is that we have one DNS hostname for three zookeeper ensemble
> >> IP.
> >> Since five node ensemble allows 2 node failure for quorum, we can do
> >>
> >>
> >> 0. First all two new ensemble IPs
> >>
> >> 1. change all three existing node config (zoo.cfg) and add two new node
> >> information
> >>    Restart all three existing nodes in a sequence.
> >>
> >> 2. Replicate the new existing zoo.cfg to two new ensemble
> >>    Start Zookeeper on two new server
> >>
> >>
> >> You can do this in backward sequence (0 -> 2 -> 1)
> >> In your case, you can do 0 -> 2 -> 1, I think.
> >>
> >> Chang
> >>
> >>
> >>
> >> 2011. 5. 5., 오후 9:57, Jared Cantwell 작성:
> >>
> >> > It would be acceptable to me to do this non-dynamically and
> non-rolling
> >> as
> >> > well. For example, I can shut down all nodes, make necessary
> >> modifications
> >> > to config files, and then restart all nodes.  If I do this, should
> >> switching
> >> > from standalone mode to multi-node mode work?  Has anyone done this
> >> before?
> >> > Preliminary tests seem to work, but I haven't looked into all the race
> >> > conditions and such yet.
> >> >
> >> > ~Jared
> >> >
> >> > On Thu, May 5, 2011 at 12:02 AM, Alexander Shraer <
> shralex@yahoo-inc.com
> >> >wrote:
> >> >
> >> >> Hi Jared,
> >> >>
> >> >> Currently there is no support for adding and removing zookeeper nodes
> >> >> dynamically. See:
> >> >> https://issues.apache.org/jira/browse/ZOOKEEPER-107
> >> >>
> >> >> We're currently working to add this feature. However, AFAIK there is
> no
> >> >> intention to support
> >> >> transformation between standalone and multi-node modes, only
> membership
> >> >> changes in multi-node mode.
> >> >>
> >> >> Regards,
> >> >> Alex
> >> >>
> >> >>
> >> >>> -----Original Message-----
> >> >>> From: Jared Cantwell [mailto:jared.cantwell@gmail.com]
> >> >>> Sent: Wednesday, May 04, 2011 7:17 PM
> >> >>> To: zookeeper-user@hadoop.apache.org
> >> >>> Subject: Growing a cluster
> >> >>>
> >> >>> Hello,
> >> >>>
> >> >>> Say I was going to grow a cluster from 1 node to 3 nodes.  Is this
> >> >>> possible,
> >> >>> and what would be the recommended way?
> >> >>>
> >> >>> At first I was thinking that I could go from 1 to 2 and then 2
to 3,
> >> >>> and it
> >> >>> seems to be working actually.  But I'm not sure if this is
> supported,
> >> >>> mostly
> >> >>> because in standalone mode the on-disk files are different than
they
> >> >>> are in
> >> >>> a multi-node configurations.  Mutli-node configurations embed the
> >> >>> quorum
> >> >>> incarnation into the filename, which standalone does not.  Should
a
> >> >>> quorum
> >> >>> node be able to startup using snapshots and logs that a standalone
> node
> >> >>> wrote out?  Is there a way around this?
> >> >>>
> >> >>> Thanks,
> >> >>> Jared
> >> >>
> >>
> >>
> >
>

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