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From Pushkar Raste <pushkar.ra...@gmail.com>
Subject Re: restore quorum after majority of zk nodes down
Date Sat, 31 Oct 2015 02:12:21 GMT
We need bounce it, but outage will be very short and you don't have to take
down rest of the zookeeper instances.

On 30 October 2015 at 11:00, Daniel Collins <danwcollins@gmail.com> wrote:

> Aren't you asking for dynamic ZK configuration which isn't supported yet
> (ZOOKEEPER-107, only in in 3.5.0-alpha)?  How do you swap a zookeeper
> instance from being an observer to a voting member?
>
> On 30 October 2015 at 09:34, Matteo Grolla <matteo.grolla@gmail.com>
> wrote:
>
> > Pushkar... I love this solution
> >       thanks
> > I'd just go with 3 zk nodes on each side
> >
> > 2015-10-29 23:46 GMT+01:00 Pushkar Raste <pushkar.raste@gmail.com>:
> >
> > > How about having let's say 4 nodes on each side and make one node in
> one
> > of
> > > data centers a observer. When data center with majority of the nodes go
> > > down, bounce the observer by reconfiguring it as a voting member.
> > >
> > > You will have to revert back the observer back to being one.
> > >
> > > There will be a short outage as far as indexing is concerned but
> queries
> > > should continue to work and you don't have to take all the zookeeper
> > nodes
> > > down.
> > >
> > > -- Pushkar Raste
> > > On Oct 29, 2015 4:33 PM, "Matteo Grolla" <matteo.grolla@gmail.com>
> > wrote:
> > >
> > > > Hi Walter,
> > > >       it's not a problem to take down zk for a short (1h) time and
> > > > reconfigure it. Meanwhile solr would go in readonly mode.
> > > > I'd like feedback on the fastest way to do this. Would it work to
> just
> > > > reconfigure the cluster with other 2 empty zk nodes? Would they
> > correctly
> > > > sync from the nonempty one? Should first copy data from zk3 to the
> two
> > > > empty zk?
> > > > Matteo
> > > >
> > > >
> > > > 2015-10-29 18:34 GMT+01:00 Walter Underwood <wunder@wunderwood.org>:
> > > >
> > > > > You can't. Zookeeper needs a majority. One node is not a majority
> of
> > a
> > > > > three node ensemble.
> > > > >
> > > > > There is no way to split a Solr Cloud cluster across two
> datacenters
> > > and
> > > > > have high availability. You can do that with three datacenters.
> > > > >
> > > > > You can probably bring up a new Zookeeper ensemble and configure
> the
> > > Solr
> > > > > cluster to talk to it.
> > > > >
> > > > > wunder
> > > > > Walter Underwood
> > > > > wunder@wunderwood.org
> > > > > http://observer.wunderwood.org/  (my blog)
> > > > >
> > > > >
> > > > > > On Oct 29, 2015, at 10:08 AM, Matteo Grolla <
> > matteo.grolla@gmail.com
> > > >
> > > > > wrote:
> > > > > >
> > > > > > I'm designing a solr cloud installation where nodes from a single
> > > > cluster
> > > > > > are distributed on 2 datacenters which are close and very well
> > > > connected.
> > > > > > let's say that zk nodes zk1, zk2 are on DC1 and zk2 is on DC2
and
> > > let's
> > > > > say
> > > > > > that DC1 goes down and the cluster is left with zk3.
> > > > > > how can I restore a zk quorum from this situation?
> > > > > >
> > > > > > thanks
> > > > >
> > > > >
> > > >
> > >
> >
>

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