On 16.5.2013 15:34, Wietse Venema wrote:
We can try to arrange some kind of online meeting about this someday if
you wish. It would be even better to have a real whiteboard around, but
we can try.
How much time do you have? I estimate this will take 3-4 sessions
of about 3-4 hours each, 1-2 per weekend. Obviously that can't be
done primarily by keyboard. In the worst case we may have to set
up some temporary account to keep international phone charges
under control.
Very little these days, but it's something I can plan for in a longer
term. I'll get in touch off-list about this...
Just be aware that persistent backlog will also affect geylisted
mail, as the time to make one pass over the deferred queue increases
with backlog size. Increasing the maximal_backoff_time only delays
the onset of trouble.
I was thinking about related issue today, too. The enhancement I was
considering was that rather than classifying all deferred mail as
"slow", we can exclude deferred mail which is not in the deferred queue
for longer than some configurable time (explicit retry count might be
even better, but we don't keep track of that now). That would prevent
the greylisted mail from being put into the same class as the entire
backlog, which might be too harsh for fresh deferred mail.
That is an optimization for near-empty deferred queues, but does
not address the concern that I raise above. Aside from that, your
optimization does not seem to introduce new worst-case behavior so
it is mostly harmless.
Right.
That huge backlog issue could be theoretically solved by introducing
additional queue which would keep the deferred mail only for some
limited time. I say theoretically, as in practice I don't think it's
very likely we would want to introduce another queue at this moment.
What we might do, though, is to introduce time-dependent fallback relay,
which would be used for deferred mail only after it was in the queue for
some time, similar to what Viktor mentioned. That way, the amount of
mail in the deferred queue is considerably limited, and only older mail
is moved to the fallback relay. This way the greylisted mail would have
much better chance of getting delivered, compared to current state, and
both machines could be IMO tuned more appropriately. One could even
setup a cascade of few more if desired...
Patrik
