On Thu, 17 Aug 2006, Peter D. Gray wrote:
> After 10 messages are injected via SMTP on the same
> connection, further messages are placed in the queue
> rather than being handled immediately.
<snip>
> Can someone explain the rationale behind such a low value?
The rationale for having a limit is that otherwise Exim starts a
delivery process for each message as soon as it arrives, and if 1000
arrive quickly you would suddenly have 1000 delivery processes all
trying to run at once.
> It would seem to me that treating messages delivered in the
> same connection differently to those arriving
> on different connections is not actually that helpful
> but maybe I just have not thought this through enough.
You can limit the number of different connections. If you have set that
to, say, 100, and messages come in very fast over those 100, you might
have (with the default setting) 1000 deliveries going on simultaneously,
but no more. Without the limit on each individual connection the number
could get a lot higher. Agreed, it's unlikely that all 100 connections
will be spewing messages in this fast, but some limit is needed IMHO.
As to the value of 10, well, yes, it's small. Partly that was me being
conservative, and partly it's because it was invented some time ago
(1998) when machines were less powerful, and partly it's because most
connections only send one message anyway...
--
Philip Hazel University of Cambridge Computing Service
Get the Exim 4 book: http://www.uit.co.uk/exim-book
