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From Cameron McKenzie <mckenzie....@gmail.com>
Subject Re: Ensure there is one master
Date Tue, 26 Nov 2013 22:34:20 GMT
If I'm understanding your question correctly, you're worried that when the
current 'master' loses its connection to ZooKeeper, a new 'master' will be
elected and you will have 2 'master' nodes at the same time. As soon as you
lose a connection to ZooKeeper there are no guarantees about any of the
state that you're determining from it. When you lose the ZooKeeper
connection, your 'master' must assume that it is no longer a 'master' node
until it reconnects to ZooKeeper, at which point it will be able to work
out what's going on.

If you look at Apache Curator, its implementation of the Leader latch
recipe handles this loss of connection and reestablishment.


On Wed, Nov 27, 2013 at 9:28 AM, ms209495 <jezdnia@gmail.com> wrote:

> Thanks for the reply. I want to clarify one thing.
> I think about a System of 20 nodes, that uses ZooKeeper of 3 nodes.
> I think about master election among these 20 nodes, that do not run
> consensus, but they use zookeeper service for master election.
> I used 'leader' term for a leeder in Zookeeper (among 3 nodes), and
> 'master'
> term for master in the System (20 nodes).
> Solution is described here:
> http://zookeeper.apache.org/doc/trunk/recipes.html#sc_leaderElection (I
> would name it 'master' election, not 'leader' election), but I doubt if it
> works reliable without additional timing assumptions as I described in my
> previous post.
> Please consider my previous post in the context of the System that uses
> Zookeeper (not ZooKeeper itself).
> --
> View this message in context:
> http://zookeeper-user.578899.n2.nabble.com/Ensure-there-is-one-master-tp7579367p7579376.html
> Sent from the zookeeper-user mailing list archive at Nabble.com.

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