Re: hash_queue_depth for better performance

From: Claus Assmann (ca+)
Date: Fri Oct 26 2001 - 22:24:31 EDT


On Fri, Oct 26, 2001, Wietse Venema wrote:
> Claus Assmann:
> > On Fri, Oct 26, 2001, Wietse Venema wrote:
> >
> > > (*) Sendmail and exim use a queue file name that is based entirely
> > > on the time of day in seconds and the process ID (plus some in-process
> > > counter). This may cause loss of mail when clocks jump or when
> >
> > I have to admit I'm disappointed to read such a statement from you.
> > sendmail will not lose mail because of that.
>
> I would like to stand corrected. How does sendmail cope with jumping
> clocks?

If the file exists sendmail won't use it. The chance for collisions
is very small.

> > > process IDs come from a random number generator (the latter happens
> > > with some UNIXes).
> >
> > sendmail has a compile time option for that (set for OpenBSD) (and
> > even if it is not set: sendmail won't lose mail in that case either).
>
> That compile time option works only for cyclic PID assignment not
> for random allocation.

It does. OpenBSD does random allocation. The trick is simple (but
off topic for this list). We asked the maintainer of some mailing
lists on OpenBSD machines for statistics, after the compile time
option has been enabled the occurrences of the problem dropped
from less than 0.1% to 0.

Sorry for the interruption, I just wanted to avoid misinformation
about other software.

[Cc'ed to the list because porcupine.org rejects mail from
my home machine. Maybe my mailrouting trick via a different
machine works.]
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