[Mailman-Developers] Regarding Handlers/SMTPDirect.py and "chunkify"

[Stefan Förster]

Hello there,

I don't really know how to start this topic, I'm fairly new to Mailman
and I don't speak anything but the most basic Python, but I am unsure
whether the function "def chunkify(recips, chunksize):" which is
defined in "Mailman/Handlers/SMTPDirect.py" might not have an adverse
effect on mail delivery performance.

The problem is: At the moment, I'm looking at a specific setup without
knowing anything about the "historical" development of "chunkify".
There is a comment which mentions an initial suggestion made by Chuq
Von Rospach and further improvements made by Barry Warsaw.
Unfortunately, I was unable to find these original discussion, and
frankly, without knowing why "chunkify" is implemented the way it is,
I don't think I'm qualified to discuss my concern (which involves VERP
delivery using a specific MTAs VERP implementation and a highly I/O
saturated mail server) on this list.

What I found out from the archives is that "chunkfiy" has two
purposes:

1. Make sure that not more than mm_cfg.SMTP_MAX_RCPTS are passed to
the MTA in a single transaction.
2. To improve delivery performance by grouping destinations which will
prevent messages which are addressed to dead/congested destinations
blocking delivery of messages to working destinations.

Is this assumption of mine basically correct? If it is and if I didn't
miss any important parts, I would like to point out a specific
scenario in which the way "chunkify" is implemented and the way in
which it is called based on delivery style (verp, bulk) and the
setting of mm_cfg.SMTP_MAX_RCPTS might actually worsen overall mail
delivery performance.

If I am totally wrong and "chunkfiy" serves a totally different
purpose, please feel free to ignore this posting.


Cheers
Stefan