[Dovecot] Issues with Dovecot/Pam/nss_ldap

[Ejay Hire]

Hello all.

I have experienced an unusual behaviour from dovecot which I believe to be
related to some interaction between dovecot and nss_ldap/Pam.

Centos/Postfix/mbox(es)/Openldap/dovecot.  The box is using PAM with ldap,
and is also running BIND, SAMBA, and DHCPD.  Dovecot 1.0rc2 from source.

I left dovecot at the default, to use PAM for authentication and guess the
mailbox.  This worked well, except during peak times, dovecot would "hang",
waiting an exceptionally long time after connecting before doing
authentication.  The users would report this as "Send/receive stuck on 64%"
or something like that.  During this time, I would note a number of
<defunct> dovecot processes in ps.  Increasing the number of idle login
proceses in the pool to ridiculously high values (30) did not affect the
symptom.  Restarting dovecot would immediately resolve the issue.

I believe this to be related somehow to dovecot's PAM interaction, because I
was able to work around it by setting dovecot to talk directly to LDAP.
Googling found isolated reports of similar behaviour in the Fedora Core 3
bug list at Redhat.

It's rare I can help in project as important as dovecot, so I'm willing to
spend some time tracking this down.  

What information can I provide to help?

Thanks
Ejay Hire