At 9PM +0000 on 12/02/13 you (Jason Lock) wrote:
Mail Issues - FreeBSD
Hello, my apologies if this may be the wrong forum but hoping that maybe someone might be able to provide some insight.
This may turn out to be something better addressed on freebsd-stable, but this is a perfectly good place to start.
Thank you for your reply.
Have a very sporadic and strange issue with our mail servers running Dovecot on FreeBSD. There are three servers hosting Dovecot with FreeBSD as the underlying operating system. All three connect to a NAS server, again running FreeBSD and ZFS.
Over NFS, I assume? What version, what mount options, and what type of authentication?
Yes, using NFSv3 to attach the share from the NAS to each of the POP3/IMAP servers. Only mount options set are RW. Not authentication in place, NAS and POP3/IMAP Servers share VLAN just for the NAS connections.
What locking strategies is Dovecot using?
In dovecot using the following:
dotlock_use_excl: no mail_nfs_storage: yes mail_nfs_index: yes lock_method: dotlock
Are there any suspicious messages in syslog on either machine?
Nothing specific.
When the specific issue occurs, clients connecting to check mail via POP3 or IMAP experience long delays and timeouts. To the point where POP3 Logins fail due to the timeouts. The issue is further compounded by clients increasing the number of attempts to check mail.
Are the delays happening before or after login?
Delays appear during login, username gets passed but then timeouts after the password is sent.
If you can provoke this and get a 'procstat -k' for the relevant dovecot process this might be helpful. If 'long' delays means >> several minutes, running something along the lines of 'procstat -k $(pgrep -U dovecot -U doveauth)' every minute or so for a >> while might be one way to catch this, though this will collect a lot of data rather fast so you will need some way to locate the >> relevant entry.
Will look to capture that information if possible, have not been able to re-create the situation in which the issue occurs.
Ben