Re: [exim] sqlrelay

Alexandre Busquets wrote:

> Can exim4 works with sqlrelay.

'Yes, but'

We use PostgreSQL extensively for Exim virtual-domain
configuration, but do not recommend it to others as anything
close to an optimal methodology.

SQLRelay

- has value for many things where very heavy DB access is
needed, but the time required - and permitted - to process an
smtp mail delivery seldom falls into that category.

- potentially reduces the certainty of having the most current
information

- is not likely to speed-up return of SQL calls by as much as
more robust methods that do not use SQL 'directly'.

- increases the number of daemons required to be functioning
correctly, thereby reducing overall reliability.

I would instead suggest that you consider exporting the SQL DB
information you need to 'read only' CDB or similar, light, fast
constructs, even flat files - then configuring Exim to read from
those.

Look also to use of a 'trigger' rather than a chron process to
automatically export updated information whenever a relevant
change is made to the DB.

Worst case, should the DB be offline, a changed password, new or
cancelled user, etc. may not be immediately actioned. But that
would be a problem even if Exim were directly accessing the
'failed' DB.

By use of intermediate quasi-static CDB or flat files, you not
only simplify calls and gain speed, but also insure that
messages can at least be received and stored with reasonably
current information - even if/as/when the master DB is 'hors de
combat'.

This also lends itself to use of a centralized DB, perhaps with
a 'user friendly' interface for preference settings, that can
exist on, and be backed up from, one server, yet reach out and
configure a great many now simpler and more robust servers that
do not themselves need to run an RDBMS engine at all.


JM2CW, YMMV

Bill