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From Camille Fournier <cami...@apache.org>
Subject Re: zookeeper deployment strategy for multi data centers
Date Fri, 03 Jun 2016 20:29:02 GMT
I wish I had a better answer for you but you can't safely and automatically
have a setup across 2 datacenters where you can be guaranteed that the loss
of one data center won't cause the cluster to go down. So, what you want to
do, you cannot do. I wrote a bit about designing x-dc ZK clusters a while
ago, not sure if any of it is relevant to you but you can read it here:
http://www.elidedbranches.com/2012/12/building-global-highly-available.html

On Fri, Jun 3, 2016 at 3:55 PM, Nomar Morado <j316services@icloud.com>
wrote:

> Will be using ZK with Apache Kafka and don't know if I can get away of not
> using ZK
>
>
>
> Printing e-mails wastes valuable natural resources. Please don't print
> this message unless it is absolutely necessary. Thank you for thinking
> green!
>
> Sent from my iPhone
>
> > On Jun 3, 2016, at 3:51 PM, Camille Fournier <camille@apache.org> wrote:
> >
> > You could put the remaining available node in read-only mode. You could
> > reconfigure the cluster to have the majority nodes in the remaining data
> > center, but it would require reconfiguration and restart of the nodes in
> > the living data center. But there's no automatic fix for this, and if you
> > can safely override the quorum rule for your application perhaps you
> don't
> > need to use ZK at all?
> >
> > On Fri, Jun 3, 2016 at 3:44 PM, Nomar Morado <j316services@icloud.com>
> > wrote:
> >
> >> Thanks Shawn.
> >>
> >> Is there any settings to override the quorum rule? Would you know the
> >> rationale behind it?
> >>
> >> Ideally, you will want to operate the application even if at least one
> >> data center is up.
> >>
> >> Thanks.
> >>
> >>
> >> Printing e-mails wastes valuable natural resources. Please don't print
> >> this message unless it is absolutely necessary. Thank you for thinking
> >> green!
> >>
> >> Sent from my iPhone
> >>
> >>>> On Jun 3, 2016, at 9:05 AM, Shawn Heisey <apache@elyograg.org>
wrote:
> >>>>
> >>>> On 6/2/2016 4:06 PM, J316 Services wrote:
> >>>> We have two data centers and got two servers at each. At an event of
a
> >>>> data center failure, with the quorum majority rule - the other
> >>>> surviving data center seems to be no use at all and we'll be out of
> >> luck.
> >>>
> >>> You are correct -- the scenario you've described is not fault tolerant.
> >>>
> >>> When setting up a geographically diverse zookeeper ensemble, there must
> >>> be at least three locations, so if there's a complete power or network
> >>> failure at one location, the other two can maintain quorum.  One
> >>> solution I saw discussed was a fifth tie-breaker server in a cloud
> >>> service like Amazon EC2, or you could go full-scale with two more
> >>> servers at a third datacenter.
> >>>
> >>> Thanks,
> >>> Shawn
> >>
>

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