Re: [Exim] Resource limiting

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Autor: Philip Hazel
Fecha:  
A: Martijn Grendelman
Cc: exim-users
Asunto: Re: [Exim] Resource limiting
On Thu, 6 Feb 2003, Martijn Grendelman wrote:

> Please tell me if I understand this correctly:
> - I have none of these options set in my config file, so defaults apply
> - smtp_accept_max = 20
> - smtp_acccept_queue_per_connection = 10
> - therefore the maximum number of Exim processes that can run simultaneously
> is 20 * 10 = 200 ?


Controlling "the maximum number of Exim processes" is not simple because
of the distributed way it works.

The maximum number of Exim processes that are accepting incoming SMTP
connections is 20. That's what smtp_accept_max says.

When one of these 20 processes has accepted a message, it normally
starts a delivery process for that message, then goes on to receive more
messages (if the client choses to send them). However, if a single
accepting process accepts more than 10 messages, it just puts any
subsequent ones on the queue, without starting a delivery process.
That's what smtp_acccept_queue_per_connection says.

So the maximum number of simultaneous processes isn't exactly
predictable. (And note that a delivery process will also run
subprocesses.)

> In other words, I am looking for a way to limit that number in a sensible
> way. I don't really like denying connections too soon, but I don't mind
> postponing delivery a bit if that helps.


Well, that's what the controls are supposed to achieve. However, 20 is
quite a small number.

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