suse.de dovecot issues

[Bernhard M. Wiedemann]

Hi,

I am one of the people taking over our new suse.de email setup
(consisting of dovecot+rspamd+postfix)
and wanted to report some issues we experience:


1.
we use dovecot-director to distribute users between 2 backend servers
that share an NFS mount.
We found that it proxies lmtp to a different backend than imap of the
same user and that caused NFS stale-filehandle errors on the
dovecot-uidlist.
It then proceeds to re-generate the dovecot-uidlist with new UIDs that
creates trouble for users.

a) shouldn't dovecot use locks (fcntl or flock) to protect such files
from concurrent updates?

b) could it generate uidlist in a way that re-generating it, assigns the
same UIDs again? E.g. via hash over file content

c) how to get dovecot-director to send all traffic for a user to one
backend?


2.
We have 2 backends so that we can do maintenance on one of them while
users can still access their emails through the other backend.
However, we found that stopping dovecot on one backend left users unable
to access their mails.
Maybe this is related to how user auth works?
How to get this HA setup right, so that we don't have a single point of
failure?


grep PRETTY /etc/os-release
PRETTY_NAME="SUSE Linux Enterprise Server 15 SP3"

rpm -q dovecot23
dovecot23-2.3.15

https://www.zq1.de/~bernhard/temp/dovecot/ has some sysreports.

Ciao
Bernhard M.