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Load-average based SMTP receiver blocking ?
- To: zmailer@nic.funet.fi
- Subject: Load-average based SMTP receiver blocking ?
- From: Matti Aarnio <mea@utu.fi>
- Date: Thu, 5 Jan 1995 17:14:01 +0200 (EET)
Hello,
I have been asked for several times to introduce such
a feature, and now it exists for a few initial platforms.
(Pick the "loadavg" extraction code from "top" program,
and place it into the smtpserver/loadaver.c ... )
At the moment the default value is 10 (!), next dump will
have it as 999 ( ftp.funet.fi blocks for the most of the
day if it is anything under 50 :-/ )
I have a couple questions regarding the feature:
When the host load-aver is over the limit, should
it respond with:
a) Connection Refused (meaning that it should
shut down the listen-socket, and be wakefull
to spot the load-drop for re-init..)
( This is COMPLEX thing to do :-/ )
b) Immediately at connection formation respond
"400 Sorry, the system is too loaded.."
and hangup
( Implemented, works -- ftp.funet.fi experience.. )
c) Accept EHLO/HELO, and then check who is
sending (glob-matching a pattern), and use
individual load-averages for each contacting
site -- thus hang-up only AFTER EHLO/HELO.
( The hooks are in the upcoming dump.. )
d) Some combination of the b+c ?
(absolute top loadmax + lower limits for
individual sites..)
In the "c"-case there would be a change to give service to
local users (like PCpine, Eudora), while blocking external
feeders.
Can you present arguments pro/cons about any of these ?
(And what that code should be ? 466 ?)
/Matti Aarnio <mea@utu.fi> <mea@nic.funet.fi>