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

[Anand Avati]

On Wed, Jun 26, 2013 at 8:04 AM, Jeff Darcy <address@hidden> wrote:

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.

To figure out which connection a client has to use, we could do auto-discover at the time of GETSPEC depending on which network interface the GETSPEC request is coming in from. We already have per transport client volfiles (one for tcp, one for rdma), and extending it to per network is natural. Today we ask the client to specify the transport type in GETSPEC (e.g "volname.rdma") - but even that can be retired if we start using getsockname() and discover the incoming interface.

This way the client only specifies the appropriate (routable) mount server IP and everything else is resolved automatically.

Another approach might be to just store the UUID of the host in the client volfile, as remote-uuid (instead of remote-host option). The client can query the mount server to resolve the UUID to a host at that point in time with a HOSTMAPPER service (like our PORTMAPPER server which maps bricks to ports). This hostmapper can maintain the relationship of all the host UUIDs in the trusted pool to all their respective interface IPs, and use the interface of the incoming mapping request to perform appropriate mapping. When in doubt, it can always return the entire set of IPs of a host (with transport types) and let the client figure out which of those IPs are routable and maybe even autodetect which is the fastest. E.g your server might have both 1g/e and 10g/e, and only some of your clients have 10g/e. In such cases this kind of auto discovery at mount time might be desirable.

Thoughts?

Avati

Avati