On Sat, Jun 20, 2015 at 04:48:24PM +0000, Adam Roses Wight wrote:
> Attaching my WIP patch here...
>
> On Sat, Jun 20, 2015 at 04:37:11PM +0000, Adam Roses Wight wrote:
> > Many hosting providers limit the number of outbound SMTP connections over
> > time, and exceeding their threshold results in harsh consequences like
> > dropped connections and unpredictable delays until recovery. It would be
> > ideal if Postfix supported absolute outbound limits.
> >
> > Currently, the only workarounds I've found are either complex or have
> > unwanted side effects.
> >
> > There's a precendent for limiting traffic by, the following
> > configuration parameters limit by destination, for example:
> > * default_destination_concurrency_limit
> > * default_destination_rate_delay
> >
> > I'm proposing that we implement the following configuration parameter,
> > which rate limits an entire transport regardless of destination:
> >
> > default_rate_delay (default: 0s)
> > The default amount of delay that is inserted between deliveries.
> >
> > To enable the delay, specify a non-zero time value (an integral value
> >
> > plus an optional one-letter suffix that specifies the time unit).
> >
> >
> > I've started writing this feature to determine whether it's feasible
> > with the current architecture, but no success yet, this doesn't seem
> > to limit the number of jobs which are popped from the queue:
> >
> > https://github.com/vdukhovni/postfix/compare/master...adamwight:rate_delay
If there is to be a global rate delay, the transport process limit
might as well be equal to 1. At which point to implement a rate
delay, it suffices for each delivery to take a minimum amount of
time, so an option along the lines of:
smtp_minimum_delay = 0s
would do the trick, by having the smtp_delivery_agent sleep if
necessary to ensure that deliveries take at least that amount of
time.
This would require no changes to the queue manager, which is a
rather complex program that is best left as-is.
--
Viktor.
