Wendigo Thompson:
> Victor:
>
> I wanted to use Postfix as a delivery mechanism so that I would be
> able to queue and hold mail during database outages and other
> maintenance -- a job that it does very well. Is there really no
> advice available on how to increase the speed of Postfix's local mail
> delivery?
I'm the guy who wrote Postfix.
With your numbers, 300k messsages/day and 3ms/delivery, the whole
day's volume should be done in about 900s. Since you see deliveries
draining into the weekend, your numbers don't seem to add up.
In the Postfix logs you can see how long it took to deliver mail.
Here is an example of a pipe alias that handles all my own email:
Jan 14 00:08:51 spike postfix/local[98331]: 9F53A1F3EA5:
to=<xxx>, relay=local, delay=0.41,
delays=0.37/0.02/0/0.03, dsn=2.0.0, status=sent (delivered
to command: yyy)
Here, it took 0.03 seconds to deliver a small message for "xxx" to
a small program "yyy". In addition it took 0.37s+0.02=0.39s to
receive the message and schedule it for delivery. This message
arrived via a slow connection. More information about this is at
http://www.postfix.org/postconf.5.html#delay_logging_resolution_limit
Now, If you want to deliver hundreds of thousands each day to a
pipe alias, then executing a whole program each time is expensive,
but it is possible if your machine has enough horse power.
So, we have two options:
a) The "red" option: to waste more resources, increase concurrency,
by increasing local_destination_concurrency_limit (default: 2).
b) The "green" option: instead of wasting CPU cycles with a local(8)
pipe alias that executes and terminates one program per delivery,
use transport_maps to direct mail to a persistent SMTP or LMTP
process that keeps the database connection open. This is the
option that Victor suggested.
Wietse
