Suddenly "too many simultaneous mail messages"

Vernon Schryver
Tue Feb 24 22:29:21 UTC 2004

> From: Spike Ilacqua 

> I'm suddenly having a rash of "too many simultaneous mail messages"
> errors.  After reading though the archives, I rebuild dccm with a bigger
> "FD_SETSIZE" (since it doesn't have anything to do with reality on
> FreeBSD) which doubled the size of max_max_work (from 190 to 395) and
> let me use "-j 350" raise maxjobs.  But I still get "too many
> simultaneous mail messages", just less often.

The next version (which I'll ship when I have a few more of the
many problems with dccproc on WIN32 squashed) will use poll() 
instead of select() when possible on FreeBSD.  That will let you
use larger -j values. 

(I don't understand what you mean by FD_SETSIZE being unreal in any
select() implementation that uses arrays of bits.  I've not been
paying attention; has FreeBSD replaced the classic 4.* BSD select()
with something like the Winsock 2.0 tactic or a wrapper for poll()?)

> Any thoughts?  One I had was to replace select() with kevent() (which
> doesn't have limitations on the number file descriptors it can handle)
> and then base max_max_jobs directly on max file descriptors (which is
> huge on FreeBSD).  But I don't know enough about DCC's internals to know
> if this would work.

Never mind dccm-dccifd.  Are you sure you want to support or allow
more than 350 simultaneous incoming SMTP transactions per SMTP server?
If each SMTP transaction takes the fewer than 2 or 3 seconds it should,
that amounts to more than 1 million mail messages per server.  Many
SMTP servers hand such loads, but it is best to jump into them knowingly.

Vernon Schryver

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