Re: [exim] Default enabling of dnsdb

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Autor: Mike Cardwell
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A: exim users
Assumpte: Re: [exim] Default enabling of dnsdb
W B Hacker wrote:

>> I'd like to petition for a change in the default makefile for 4.70 such
>> that DNSDB is enabled by default. In the comments it says:
>>
>> # LOOKUP_DNSDB does *not* refer to general mail routing using the DNS.
>> # It is for the specialist case of using the DNS as a general database
>> # facility (not common).
>>
>> I agree that using DNSDB is specialist, but I think its usage is common
>> enough for it to be enabled by default.
>>
>> I can't see any disadvantage to it being compiled in... I just compiled
>> Exim with it, and then again without it and the difference between the
>> two binaries was a mere 4285 bytes... Most *emails* are bigger than 4285
>> bytes these days...
>>
>> Does anyone agree/disagree with me strongly?
>
> Disagree on general principle.


I thought you might.

> Putting seldom-used 'features' into defaults seems harmless a few bytes
> at a time...
>
> And this one-more-small-chunk may or may not affect resources needs.
>
> But it means more code to maintain and debug 'forever' - not just document.
>
> Note that we've just seen moves to pull perl and such *out* of the defaults.
>
> And that 'real' DB's (PostgreSQL, mySQL, et al) need to be optioned IN,
> not OUT.
>
> KISS
>
> Exim is not competing with the Linux kernel for bloat.
>
> JM2CW


The examples you gave there re postgresql, mysql and perl are hardly
equivalent to the ability to do arbitrary DNS lookups. DNS is an
essential part of routing mail in general, whereas the others aren't.
DNSDB doesn't require linking in extra third party libraries whereas the
others do. Also, the "bloat" comment is clearly over the top.

It's a shame that despite this, DNSDB is a "database lookup". Perhaps
Philip didn't fully forsee how the lookup type would be used. I'm not
going to get into an argument about the symantics there though.
Something like one of these might have been more appropriate to be
compiled in by default:

${dns{ns}{example.com}} which would return a domainlist
${dns{a}{example.com}} which would return a hostlist

etc

--
Mike Cardwell
(https://secure.grepular.com/) (http://perlcv.com/)