[Mailman-Users] Adding backup to multi-server config

[Jeff Taylor]

I have been running mailman 2.1 from three servers with NFS sharing for
the past couple years, but due to a recent issue I did some digging and
found the suggestions for clustering at
http://mail.python.org/pipermail/mailman-users/2008-March/060753.html
(the post by Mark Sapiro detailing how to set up qrunner slices).  It
turns out the problem I was having was user error, so apparently mailman
*can* run on a low traffic site without issue... however since I now
have the proper changes made for qrunner, I have a new question.

My network consists of three primary servers running postfix and
mailman.  These are each essentially redundant machines, and I am in the
process of setting up a fourth machine in a VM for processing SMTP. 
What I am wondering about is if there would be a way to configure
qrunner on this VM so that it only processes messages which have been in
the queue for more than X minutes... basically a backup machine so that
if the server processes one of the slices goes offline for an extended
period, this backup server would make sure the message gets sent out.

>From an initial glance, I was thinking of having a configurable Delay
variable in mm_cfg.py, specified in seconds, then qrunner could use the
timestamp on the queued messages and only process the ones which were
older than Delay.  This backup machine would *not* have the qrunner
slices patch applied to it, as it should be processing any message that
doesn't get handled by the primary servers.

Does this sound plausible?  Unfortunately I know nothing about python,
nor the specifics of mailman's code, so I'm not sure if this would be an
easy change that someone could give me the code for... but any help is
appreciated.