[Pacemaker] [RFC] [Patch] DC node preferences (dc-priority)

[Florian Haas]

On Fri, May 25, 2012 at 10:45 AM, Lars Ellenberg
<lars.ellenberg at linbit.com> wrote:
> Sorry, sent to early.
>
> That would not catch the case of cluster partitions joining,
> only the pacemaker startup with fully connected cluster communication
> already up.
>
> I thought about a dc-priority default of 100,
> and only triggering a re-election if I am DC,
> my dc-priority is < 50, and I see a node joining.

Hardcoded arbitrary defaults aren't that much fun. "You can use any
number, but 100 is the magic threshold" is something I wouldn't want
to explain to people over and over again.

We actually discussed node defaults a while back. Those would be
similar to resource and op defaults which Pacemaker already has, and
set defaults for node attributes for newly joined nodes. At the time
the idea was to support putting new joiners in standby mode by
default, so when you added a node in a symmetric cluster, you wouldn't
need to be afraid that Pacemaker would shuffle resources around.[1]
This dc-priority would be another possibly useful use case for this.

Just my two cents.
Florian

[1] Yes, semi-doable with putting the cluster into maintenance mode
before firing up the new node, setting that node into standby, and
then unsetting maintenance mode. But that's just an additional step
that users can easily forget about.

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