Re: [Exim] LDAP attribute extraction

On Mon, Aug 07, 2000 at 09:39:31AM +0100, Philip Hazel wrote:
> Exim just hands the query over to LDAP - using the ldap_url_search()
> function. It doesn't try to be clever about analysing the query in any
> way. (That was supposedly the beauty of using this interface - leave the
> work to somebody else. :-)
>
> It occurs to me that a sensible LDAP search engine should be doing its
> own caching. Do you have any information on whether this is actually the
> case?

I notice there is a function ldap_enable_cache in the OpenLDAP SDK. But it
doesn't say whether it does 'clever' re-use of queries, or just returns
the results from identical queries.

That's for client-side caching. As for server-side, well that's very
implementation-specific of course, but it will still have a certain amount
of work to do even in processing the messages coming down the TCP connection
and looking up in the cache.

> I would not
> recommend using LDAP for local_domains. Exim makes quite a lot of use of
> local_domains for a number of different reasons. This is not the only
> example (relay checking is another). Also, if your LDAP database goes
> down, all mail is delayed.
>
> If you want your primary data to be in LDAP, one way round is to run a
> cron job to regularly extract the list of local_domains into a cdb file
> (say) for fast performance.

OK, I understand.

There is a philosophical point here; for consistency I would like _all_ the
queries to go against the LDAP database, or else extract everything into
.cdb files. But I do live in the real world as well :-)

Cheers,

Brian.