Using process priority to throttle inbound SMTP

[Tony Finch]

I use a different technique on my servers, because the load from scanning
email is pretty much constant. Deciding not to accept email based on load
is not very effective. What I do instead is count the number of messages
in the incoming queue, and defer email if this number is too large (i.e.
the machine is backlogged). This is very easy to do with Exim. In my
RCPT ACL I have:

  defer message = Sorry, too busy. Try again later.
        condition = ${run {/opt/exim/bin/exim -bpc -DSPOOL=/spool/exim.in} \
                          {${if >{$value}{300} {yes} {no} }} {no} }

Tony.
--
f.a.n.finch  <dot at dotat.at>  http://dotat.at/
ST DAVIDS HEAD TO COLWYN BAY, INCLUDING ST GEORGES CHANNEL: EAST TO SOUTHEAST
3 OR 4, GRADUALLY VEERING SOUTHWEST. MAINLY FAIR. MODERATE WITH FOG PATCHES.
SLIGHT.

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