[Pacemaker] globally-unique clone question

[Eliot Gable]

The typical usage in this case would be to make all mail servers serve all domains (virtual domain support) and then run N instances across those N servers. Then there is no per-server unique information to deal with. Then you can run, for example, load sharing between the nodes using iptables CLUSTERIP (since all nodes would then be serving the same data) and put a constraint in the CIB that says that if the clone fails on a node, pull that node from the load-sharing config by stopping or moving away your load-sharing resource. At least, that's how I would do it.


Eliot Gable
Senior Engineer
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-----Original Message-----
From: Joe Armstrong [mailto:jarmstrong at postpath.com]
Sent: Thursday, May 21, 2009 11:04 AM
To: pacemaker at oss.clusterlabs.org
Subject: [Pacemaker] globally-unique clone question

Hi All,

I am a little confused about globally-unique clones, since there can be no instance attributes for a clone how do you tell each clone that it is unique ?

My use case is that we need to run N instances of a mail server, each mail server is unique in that it serves a specific domain, two mail server can never run on the same host.  In order to provide HA we need to tell the mail server instance what domain to serve (or what filesystem to mount in order to get the right data/config).

I was thinking that using globally-unique clones would be the way to manage this (it makes the mutual exclusion rule easy: clone-node-max=1) but I don't see how to make each instance unique.

... then again I could be mis-using the concept...

Thanks for any pointers.

Joe

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