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From Todd Nine <t...@spidertracks.co.nz>
Subject Re: What roles do "even" nodes play in the ensamble
Date Wed, 25 Aug 2010 22:09:37 GMT
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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