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From Dave Wright <wrig...@gmail.com>
Subject Re: What roles do "even" nodes play in the ensamble
Date Wed, 25 Aug 2010 22:11:49 GMT
I'm not an expert on voting, so there may be a better answer, but from my
understanding all 4 nodes participate in the voting and you need a majority
of 3 to elect a leader.

-Dave

On Wed, Aug 25, 2010 at 6:09 PM, Todd Nine <todd@spidertracks.co.nz> wrote:

>  Thanks for that Dave.  If I do not configure it as an observer just a
> normal member, what will the last even node to join do?
>
>
> 1. Will it participate as a voter on startup?  (I'm assuming not, just read
> only)
>
> 2. If one of the voter nodes 1 through 3 dies, does it become a voter?
>
>
>    todd
> SENIOR SOFTWARE ENGINEER
>
> todd nine| spidertracks ltd |  117a the square
> po box 5203 | palmerston north 4441 | new zealand
> P: +64 6 353 3395 | M: +64 210 255 8576
> E: todd@spidertracks.co.nz W: www.spidertracks.com
>
>
>
>
>
>   On Wed, 2010-08-25 at 17:57 -0400, Dave Wright wrote:
>
> >
> > 1. When the 4th ZK node joins the cluster, does it take on the observer
> > role since a quorum cannot be reached with the new node?  Can I still
> > connect my clients to it and create/remove nodes and receive events?
>
> No, it joins as a normal member unless you've configured it as an
> observer. Note that with 4 nodes you now need 3 running to get a
> majority, which is why even numbers aren't recommended.
>
> >
> >
> > 2. In the event 1 of the 3 voting nodes fails, will this 4th node become
> > a voting member of the ensemble?
>
> If configured as an observer it remains an observer.
>
> >
> > 3. When a new node comes online, it may have a different ip than the
> > previous node.  Do I need to update all node configurations and perform
> > a rolling restart, or will simply connecting the new node to the
> > existing ensemble make all nodes aware it is running?
>
> Unfortunately ZK doesn't have any kind of dynamic configuration like
> that currently. You need to update all the config files and restart
> the ensemble.
>
> -Dave Wright
>
>

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