On Thu, 1 Sep 2005, Michael Haardt wrote:
> Hello,
>
> if a few hosts with the same retry rules send large amounts to a host
> that was previously down, it may happen that both experience problems with
> the restricted number of connections offered by the previously down host.
> Retrying later gets the same behaviour. It's not as extreme as it sounds,
> but to a certain amount, I do see a wave shape.
>
> How about randomising a part of geometric retry times?
That sounds extreme and complicated, difficult to explain, and liable to
errors, for what is a situation case.
Incidentally, I have often argued that the use of backup MX (currently
going out of favour) is one way to avoid this problem. The pending mail
collects on the backup and can be transferred in an orderly fashion when
the primary comes up. Of course, you then have the problem of keeping
the acceptance rules identical on the backup and the primary, so I can
see why people don't like backup MX any more. There are problems both
ways.
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book: http://www.uit.co.uk/exim-book
