Re: [EXIM] Limiting the number of simultaneous pipes

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Autor: Philip Hazel
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A: Lee McLoughlin
CC: exim-users
Assumpte: Re: [EXIM] Limiting the number of simultaneous pipes
On Tue, 27 Oct 1998, Lee McLoughlin wrote:

> I need some way of limiting the number of simultaneous pipe commands
> that can be forked off. I already limit the number of SMTP listeners
> and queue handlers and this helps a bit. I'v checked through the
> documentation and can't find anything to limit pipe transports in this
> way.


I'm afraid there isn't. It would require some kind of central file that
kept track of the number of pipe commands that were running. And that
begs lots of questions: do you want to limit *all* pipes, whatever
program they are running, or just apply a limit to each particular pipe
command, and if so should that also be per user or general? The idea
just doesn't fit nicely with the decentralised way Exim works, I'm
afraid.

Can you not arrange something on the outside? If the pipe command
returns a value that is treated as a temporary failure (see temp_errors
for the pipe transport) then Exim will defer and try again later. So you
could implement your own external counting mechanism to whatever spec
you want, and cause deferment when the count was too high.


-- 
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.



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