zookeeper-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Camille Fournier <cami...@apache.org>
Subject Re: Ensure there is one master
Date Tue, 26 Nov 2013 20:10:10 GMT
The master in part b is only a master so long as it has a quorum of
followers. It loses the quorum when the  network partitions and so will no
longer act as master from that moment.
Additionally the master actions all require a consensus to proceed. So even
if the master in section b doesn't know it is no longer the master no state
changing actions will be able to get a quorum of votes to proceed, so there
is no time in which it can improperly lead because it won't actually have
the votes to make changes.


On Nov 26, 2013 12:08 PM, "ms209495" <jezdnia@gmail.com> wrote:

> Hi,
> ZooKeeper is an excellent system but the problem with ensuring only one
> master among clients bothers me.
> Lets have a look at the situation when network partition happen: there is
> part A (majority), and part B (minority).
> Lets assume that before network partition happened the master was connected
> to part B.
> After the network partition, part A will elect new ZooKeeper leader, and
> there will be new master elected among clients connected to part A.
> At this time there are two masters - old in part B, and new in part A.
> The only solution I can think about to this problem, is to ensure that the
> new master is inactive for some time - to ensure that the old master in
> this
> time will detect that it is not connected to ZooKeeper quorum, and will
> deactivate itself as a master.
> This solution assumes that timers on these machines work correctly.
> Is it possible to ensure only one master using ZooKeeper without timing
> assumptions ?
> Thanks,
> Maciej
> --
> View this message in context:
> http://zookeeper-user.578899.n2.nabble.com/Ensure-there-is-one-master-tp7579367.html
> Sent from the zookeeper-user mailing list archive at Nabble.com.

  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message