[Gluster-devel] RFC - "Connection Groups" concept

[Jeff Darcy]

On 06/26/2013 11:42 AM, Joe Julian wrote:
> There are only two translators that use the network, server and
> client. I'm unclear how these communication groups would get
> applied.
>
> I lean a little bit toward being against solving network problems
> with application complexity. Can't these problems be solved with
> split horizon DNS and/or static routing?

Some can; some can't.  Even for those that can, some users might prefer
a solution within GlusterFS - as long as we come up with a coherent
model - instead of having to deal with DNS or iptables.  One of the
major problems that can't be solved that way is separate access controls
for each connection group.  For example, it might be desirable to allow
mounts from a particular machine (or to a particular volume) only
through a particular network - both for security reasons and to prevent
saturation of a critical network with non-critical traffic.

I think Kaushal's connection-group idea is headed in the right
direction.  We should use UUIDs as much as possible internally, as using
either DNS names or IP addresses in this context is error-prone.  There
should be a way for a CLI user to associate a "nickname" with a
particular host, using either its UUID or one of its addresses at the
moment of issuing the command.  Likewise, there should be a simple way
to associate an interface with a connection group, using any of the
interface's unique identifiers/properties at the time of association.
Attaching that connection-group ID to an incoming connection/interface
is pretty trivial, as is adding it to the "identity" that we use for
access control.

The trickier part is figuring out how to associate a connection group
with a client and route appropriately from that end.  Do we have
connection-group-specific volfiles?  How do we specify which one we
want?  Adding more options to mount.glusterfs doesn't seem all that
appealing, but I don't really see any way around it (obviously without
the options or special configuration the behavior should be as it is
now).  The glusterd changes to handle this are likely to be pretty
tedious, but IMO they're necessary to support some users' requirements.