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Subject: Re: postfix with qmail
From: Bennett Todd (betrahul.net)
Date: Tue Apr 04 2000 - 17:52:02 CDT

2000-04-04-17:22:50 Frank Auciello:
> [ getting postfix to read the cdb file written by qmail's pop3
> daemon ]

If qmail's pop3 daemon writes tcp.smtp, then rebuilds tcp.smtp.cdb
dynamically from it, then you're in fine shape; just list tcp.smtp
as a plain file in Postfix. Or, if you are worried about it getting
big enough for the linear searches to get expensive, rig a daemon to
keep an eye on it and update a db or dbm or whatever hash whenever
it changes.

If qmail's pop3 daemon directly rewrites the cdb file only, and
doesn't duplicate the information into another file format, then you
have two choices: modify the pop3 daemon to put the data into an
accessible format, or modify Postfix to link it to djb's cdb
library. Adding a new cdb map type should be relatively painless;
given the number of different map types already supported by Postfix
it must have a reasonable modular interface for adding them, and
cdb's library interface looks reasonably painless to code against.

In fact, adding a cdb map type to Postfix is probably worthwhile
anyway; it's got a lot of appeal that library does. Updates require
doing full rebuilds, but they are atomic, and the reading library is
happy with the database being replaced underneath it live; it's
guaranteed to see either the before or the after, doesn't blow up,
and notices the update on the first query that follows the update.
Also, the database is reasonably compact, and reads take just two
reads from disk (less if a large portion of the database can stay in
cache of course).

See <URL:http://cr.yp.to/cdb.html>.

-Bennett

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