Dan Caballero writes:
So is there a 1:1 relationship between the number of runners and the maximum number of messages that may be processed with .bak files in the out queue?
Yes. The way this works is the runner gets the first message in it's slice from the .pck file and renames the .pck to .bak. It then processes the message and upon successful completion removes the .bak. I.e., the .bak file contains the message currently being processed by that runner.
The purpose of the .bak is disaster recovery in case the runner gets killed (say by a power failure), when it starts again it recovers the .bak file.
See https://gitlab.com/mailman/mailman/-/blob/master/src/mailman/core/switchboar... for the details of how all this, including slicing, works.
-- Mark Sapiro <mark@msapiro.net> The highway is for gamblers, San Francisco Bay Area, California better use your sense - B. Dylan