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From Enrico Olivelli <eolive...@gmail.com>
Subject Re: About ZooKeeper Dynamic Reconfiguration
Date Wed, 21 Aug 2019 18:01:17 GMT
Il mer 21 ago 2019, 17:22 Alexander Shraer <shralex@gmail.com> ha scritto:

> That's great! Thanks for sharing.
>
> > Added benefit is that we can also control which data center gets the
> quorum
> > in case of a network outage between the two.
>
> Can you explain how this works? In case of a network outage between two
> DCs, one of them has a quorum of participants and the other doesn't.
> The participants in the smaller set should not be operational at this time,
> since they can't get quorum. no ?
>

I have recently talked about a similar problem with Norbert K. on gitter
chat.
We got to the conclusion that you need 3 datacenters

Enrico



> Thanks,
> Alex
>
> On Wed, Aug 21, 2019 at 7:55 AM Cee Tee <c.turksema@gmail.com> wrote:
>
> > We have solved this by implementing a 'zookeeper cluster balancer', it
> > calls the admin server api of each zookeeper to get the current status
> and
> > will issue dynamic reconfigure commands to change dead servers into
> > observers so the quorum is not in danger. Once the dead servers
> reconnect,
> > they take the observer role and are then reconfigured into participants
> > again.
> >
> > Added benefit is that we can also control which data center gets the
> > quorum
> > in case of a network outage between the two.
> > Regards
> > Chris
> >
> > On 21 August 2019 16:42:37 Alexander Shraer <shralex@gmail.com> wrote:
> >
> > > Hi,
> > >
> > > Reconfiguration, as implemented, is not automatic. In your case, when
> > > failures happen, this doesn't change the ensemble membership.
> > > When 2 of 5 fail, this is still a minority, so everything should work
> > > normally, you just won't be able to handle an additional failure. If
> > you'd
> > > like
> > > to remove them from the ensemble, you need to issue an explicit
> > > reconfiguration command to do so.
> > >
> > > Please see details in the manual:
> > > https://zookeeper.apache.org/doc/r3.5.5/zookeeperReconfig.html
> > >
> > > Alex
> > >
> > > On Wed, Aug 21, 2019 at 7:29 AM Gao,Wei <Wei.Gao@arcserve.com> wrote:
> > >
> > >> Hi
> > >>    I encounter a problem which blocks my development of load balance
> > using
> > >> ZooKeeper 3.5.5.
> > >>    Actually, I have a ZooKeeper cluster which comprises of five zk
> > >> servers. And the dynamic configuration file is as follows:
> > >>
> > >>   server.1=zk1:2888:3888:participant;0.0.0.0:2181
> > >>   server.2=zk2:2888:3888:participant;0.0.0.0:2181
> > >>   server.3=zk3:2888:3888:participant;0.0.0.0:2181
> > >>   server.4=zk4:2888:3888:participant;0.0.0.0:2181
> > >>   server.5=zk5:2888:3888:participant;0.0.0.0:2181
> > >>
> > >>   The zk cluster can work fine if every member works normally.
> However,
> > if
> > >> say two of them are suddenly down without previously being notified,
> > >> the dynamic configuration file shown above will not be synchronized
> > >> dynamically, which leads to the zk cluster fail to work normally.
> > >>   I think this is a very common case which may happen at any time. If
> > so,
> > >> how can we resolve it?
> > >>   Really look forward to hearing from you!
> > >> Thanks
> > >>
> >
> >
> >
> >
>

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