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Zookeeper >> mail # user >> Network partition and ephemeral nodes


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Narayanan Arunachalam 2012-11-25, 18:32
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Camille Fournier 2012-11-25, 18:49
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Re: Network partition and ephemeral nodes
To expand on this, when a client is disconnected, it receives a disconnect
event.

>From that time until the client is reconnected, the client doesn't know
what has happened.  The session may have expired or it may have not
expired.  Keep in mind that clock changes can make reasoning during this
time impossible to do with precision.

What the client does during this period of ignorance is up to the designer
of the application.  There are several potential strategies.  If the
application must have at most one master, then the disconnected client
should immediately stop behaving as a master.  If the application must have
at least one master, then the disconnected client should continue as
master.  If you have an in between strategy where it is bad but not fatal
to have two masters, you can have the disconnected client behave as a
master up to the point where it thinks that it likely has been superseded
by some other method.

Zookeeper cannot decide this issue for you.

On Sun, Nov 25, 2012 at 10:49 AM, Camille Fournier <[EMAIL PROTECTED]>wrote:

> Yes if quorum is intact but the client cannot connect to the zookeeper, the
> session and the ephemeral nodes will expire. It is up to users of ZK for
> locking to correctly assume that a given client is not the lock holder if
> its connection to the ZooKeeper is lost.
>
> C
>
> On Sun, Nov 25, 2012 at 1:32 PM, Narayanan Arunachalam <
> [EMAIL PROTECTED]> wrote:
>
> > Hi,
> >
> > In case the network between ZK cluster and client is partitioned, once
> the
> > session expires would it remove the ephemeral nodes? If that's the case
> how
> > is the correctness of the recipes like locks are archived. Because once
> the
> > ephemeral nodes are removed next client would be granted the lock isn't
> it.
> >
> > Regards,
> > Nara
>
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Narayanan Arunachalam 2012-11-25, 20:14
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Ted Dunning 2012-11-25, 21:30
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB