[ClusterLabs] Why do clusters have a name?

[Ken Gaillot]

This was a great thread. :) It also made me realize we don't document
cluster-name in Pacemaker Explained, so I'll do that for the next
release.

On Thu, 2019-03-28 at 08:30 +0000, Christine Caulfield wrote:
> On 26/03/2019 20:12, Brian Reichert wrote:
> > This will sound like a dumb question:
> > 
> > The manpage for pcs(8) implies that to set up a cluster, one needs
> > to provide a name.
> > 
> > Why do clusters have names?
> > 
> > Is there a use case wherein there would be multiple clusters
> > visible
> > in an administrative UI, such that they'd need to be
> > differentiated?
> > 
> 
> 
> Alongside the current usage there's some history here.  Originally
> (when
> cman was in the kernel) the name was used to get the correct
> information
> from the centralised cluster configuration daemon (ccsd).
> 
> After that it got used as a hash to generate a cluster_id for
> clusters
> that might be on the same network (cluster_id as a number was also
> allowed, but as name was already a field it seemed sensible to keep
> using it). The hashed cluster_id was included in the protocol so that
> clashing clusters would ignore each other's messages. In a later
> revision the cluster name was also hashed to generate a very
> primitive
> encryption key for openais if one was not provided. This was, again,
> more to provide isolation than actual security.
> 
> Of course it's used for none of those things now, but that's where it
> came from originally :)
> 
> Chrissie
-- 
Ken Gaillot <kgaillot at redhat.com>