queue.in backed up

Julian Field mailscanner at ecs.soton.ac.uk
Fri Jan 2 10:16:27 GMT 2004

At 21:27 01/01/2004, you wrote:
>I have Mailscanner running on a FreeBSD 4.6 box and last night my /var mount
>point filled up and couldn't be written to. This of course caused problems.
>Im not sure why it filled up. But anyways my queue.in directory is pretty
>full now. I have mail delivering fine but it doesnt seem to be reducing
>queue.in at all. In fact I would say it is increasing ever so slightly. How
>can I get this to start reducing? Ive noticed that SA is timing out now too.

One of the problems (fixed in recent versions) was that finding the oldest
messages in the incoming queue could actually take a long time if the queue
was very large. As a result the message flow rate could drop quite badly
when hit with a huge incoming queue and a poor filesystem. Most filesystems
appear to have to search a list of all the directory entries to find a
particular file, which is very slow if you have to do it more than once You
need to do it at least twice for every message in the queue, to get the df
and the qf files (or the equivalent queue files for other MTAs). The one
notable exception is XFS, which handles large directories much better than
most other filesystems.

That was fixed in version 4.24. From then on there has been a "Max Normal
Queue Size" setting. When the queue gets bigger than that, it switches from
processing in strict date order to processing fastest in an attempt to
clear the queue. Its behaviour is a bit more complicated than that, but
that's basically the effect you will see. I normally set "Max Normal Queue
Size" to something like 500 or 1000.

Alternatively, move all the files out of your mqueue.in to somewhere else,
and drip-feed them back into the queue. Make sure you always put back
matching pairs of qf+df files, but if you put a few hundred in at a time it
will process them a lot faster than it can with all of them there.

First solution requires an upgrade (possibly), second solution is more manual.
Julian Field
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