[Mailman-Developers] Queue questions & thoughts...

[The Dragon De Monsyne]

	I just have a question.... Peering through the queueing system, I
note that there does not seem to be any locking of the queuefiles...
Correct?  The way it appears to me that mailman is working is thus:
	every outgoing message is queued, then an attempt to feed it to
the MTA is made. After that it tries to run the queue to catch anything
waiting there. 
	What keeps another process running the queue from grabbing &
delivering the queued message whilst the first proccess is trying to send
the same message to the MTA? Especially whence you have several proccesses
rapidly forked all doing delivery at once?

	Here's the situation I'm worried about:
 Proccess 1 queues the message, and attempts to feed it to the MTA
 Proccess 2 running queue reads the queued message, and also attempts to
       deliver it to the MTA.
 Proccess 1 succeeds in in delivering the message and deletes it from the
       queue.
 Proccess 2 ALSO succeeds in delivering the message, creating a duplicate.
 Proccess 2 tries to delete the message from the queue, and can't since
        proccess 1 already deleted it, generating this traceback, which
        I _have_ seen in my error log: 

Aug 29 04:10:59 1998 contact_transport: Traceback (innermost last):
contact_transport:   File 
          "/usr/services/mailman/scripts/contact_transport", line 52, in ?
contact_transport:      OutgoingQueue.processQueue()
contact_transport:   File
          "/usr/services/mailman/Mailman/OutgoingQueue.py", line 38, in
          processQueue
contact_transport: Utils.TrySMTPDelivery(recip,sender,text,full_fname)
contact_transport:   File "/usr/services/mailman/Mailman/Utils.py", line 
          230, in  TrySMTPDelivery
contact_transport:      OutgoingQueue.dequeueMessage(queue_entry)
contact_transport:   File "/usr/services/mailman/Mailman/OutgoingQueue.py", 
          line 25, in dequeueMessage
contact_transport:      os.unlink(msg)
contact_transport: os . error :  (2, 'No such file or directory') 


	Having pointed out a possible problem, perhaps I can suggest 
a possible solution?  Howabout this:

	Whenever Mailman goes to deliver mail, it dosen't actually deliver
it. Rather, it just queues the message. Instead, there is a single,
separate proccess that is kept running, and all it does is dequeue
messsages. It would keep a PID file and touch it periodically, so you
could run a cron job to make sure it is still running. Since it would hold
no locks on any lists, it wouldn't have to worry about forking to avoid
deadlocks, and since it would be run under the mailman uid it wouldn't be
affected by any possible setgid weirdness (i.e. w/ linux)). 

	If anyone is interested in this, let me know, & I'll put
something together. It should be really quick. 


	-The Dragon De Monsyne