I just dealt with an interesting Dovecot issue on our small server, and thought
I might share it. I also feel that although in the end it was a configuration
error, Dovecot should somehow avoid leaving this processes around and hence
filling up the process limit quickly.
- set up Dovecot IMAP on Debian buster (either with the older 2.3.x Debian
package, or 2.3.14 from the dovecot-repo)
- config:
...
namespace inbox {
inbox = yes
location =
... default settings ...
...
passdb {
args = scheme=HMAC-MD5 username_format=%u /etc/dovecot/users
driver = passwd-file
}
protocols = " imap"
...
userdb {
args = blocking=no
driver = passwd
}
...
- secret sauce: have a user in the passdb that doesn't have a physical account
on the system yet (we were migrating to a new machine).
The log-file shows successful authentication for that user (after we flipped
DNS to point to this new machine), but over time (2-3 times/day) we were left
with an increasing number of `imap-login` processes in state `pre-login`,
eventually requiring a dovecot restart. Dialling up process_limits didn't seem
to help, we'd just get more of these stale processes.
After creating the user on the system, the behaviour reverted to normal, no
more stale processes. I do not know what error message that user received on
their end, but since we announced we were migrating, they probably just ignored
it and thought it as part of the transition.
Best,
Volker (a happy & long Dovecot user)
