saslauthd performance anxiety

[simon.brady at otago.ac.nz]

I've just upgraded to imapd 2.1.11, and while it's going fine so far I'm a
bit concerned about how it will cope under load when our students return.

The problem is that I'm using the saslauthd native LDAP mechanism, and the
directory it's binding to is quite slow (it's actually a slapd instance
running a shell backend which routes bind requests to different places
depending on the usercode - don't ask...). Because saslauthd makes
synchronous bind calls, it's doesn't take many concurrent requests to
exhaust the default pool of five instances.

Since it's hard to predict peak usage, I'm tempted to run the daemon with 
the -n0 option so it can spawn as required. However, a colleague has 
pointed out that if something blows up then spawn-on-demand could kill the 
server - with a fixed-size pool, auth requests would fail but the system 
would keep going.

Can anyone offer advice on tuning the saslauthd pool? Are there particular
options, either on the command line or in saslauthd.conf, which I should
be looking at?

Many thanks...
Simon

--
Simon Brady                             mailto:simon.brady at otago.ac.nz
ITS Technical Services
University of Otago, Dunedin, New Zealand