[ClusterLabs] Why do clusters have a name?

Christine Caulfield ccaulfie at redhat.com
Thu Mar 28 04:30:15 EDT 2019

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 :)


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