Re: [exim-dev] better support for macros

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Author: Philip Hazel
Date:  
To: Kjetil Torgrim Homme
CC: exim-dev
Subject: Re: [exim-dev] better support for macros
On Wed, 16 Mar 2005, Kjetil Torgrim Homme wrote:

> the enclosed patch adds support for macro definitions in the sections
> "acls", "authenticators", "routers" and "transports".


<snip>

> I would love to see this patch included upstream. thank you for your
> consideration.


While I am always happy to look at patches - I'll look at this one - I
am wary about adding anything that increases the time spent processing
the configuration file. Remember that Exim re-reads its configuration
file *very frequently*. It is only the daemon that reads it once and
then runs for ever. Other Exim processes are short-lived, and they all
have to read the configuration when they start up.

For maximum performance, it is always better to use a fixed config file
(as short as possible); you can always set up some external process to
generate such files if necessary.

Having said that:

(1) Over the lifetime of Exim, I have given in to people's requests and
added stuff like macros and .include to the config, so I suppose this is
no different. If you don't use it, it won't impact (much).

(2) Processors get faster and faster and maybe the resources needed to
process the config file are, in absolute terms, pretty trivial. So we
might as well use them to make the sysadmin's life easier...

-- 
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book:    http://www.uit.co.uk/exim-book