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From Alexander Shraer <shra...@gmail.com>
Subject Re: About ZooKeeper Dynamic Reconfiguration
Date Wed, 21 Aug 2019 15:21:45 GMT
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 ?

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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