Stefan Foerster:
> So, my question is: Are there any plans to further enhance Postfix's
> functionality as far as SMTP proxy filtering is concerned, and make
> that kind of load balancing available to pre-queue setups using
> smtpd_proxy_filter?
For TRUE load balancing you need a stateful system that remembers
which connections are going where. You could try the nginx reverse
proxy; it speaks SMTP among many protocols, and is often used for
software-based load balancing.
For STATISTICAL load balancing you can get by with multiple IP
addresses per proxy filter "host" name. However this requires new
code in Postfix to randomize the address order. You may know that
the Postfix smtpd_proxy client does not make its own SMTP connections.
Instead it uses the same Postfix library functions for making a
connection over TCP, UNIX-domain sockets, System V streams, etc.
as all other Postfix programs (except the SMTP client, which does
its own name-to-address translation). Changing this library means
changing applications that call into this library (Postfix invokes
the _connect() functions via function pointers, so a simple "#define
old(x,y,z) new(x,y,z,0)" won't do the job.
I have a bunch of deliverables in the second and third quarters
of 2010, so I must get Postfix 2.7 out in the first quarter. This
means I have few cycles left for Postfix 2.7. I would like to spend
those on postscreen.
Wietse
