dovecot - Aug 2009 - hoping someone has a suggestion

Hi using dovecot 1.0.10 with pop/imap, using maildir, with 2000+ users
mostly using pop but many using imap.

 

Once in a great while I have problems with dovecot pop timing out. If I
telnet to port 110 it just takes forever to come up or it doesn't at all,
the samething happens on the imap port although 110 is always worst. 

 

At 1st when troubleshooting I was not sure what was causing the situation
and when I ran out of options I stopped postfix. When I did this dovecot
immediately started working again, that is port 110/143 came up fast and all
the user logins were fast again. When I restarted postfix after a minute or
so dovecot became slow again.

 

While observing this situation I notice that postfix had most of the
connections about 300+ in established state, while dovecot was using around
150 connections.

After adjusting some of the parameters on postfix and shutting it down
multiple times, suddenly everything worked but this time postfix was
reporting  over 3000 connections mostly in TIME_WAIT state which is normal
for us.

 

My  question is what do you guys think is happening here, what is the
relationship between dovecot/postfix that would cause this to happen. I'm
just looking for some suggestions in case this happens again.

 

# 1.0.10: /usr/local/etc/dovecot.conf

protocols: imap pop3

ssl_disable: yes

disable_plaintext_auth: no

login_dir: /usr/local/var/run/dovecot/login

login_executable(default): /usr/local/libexec/dovecot/imap-login

login_executable(imap): /usr/local/libexec/dovecot/imap-login

login_executable(pop3): /usr/local/libexec/dovecot/pop3-login

login_greeting: D-V1 NP09 ready.

login_process_size: 384

login_processes_count: 55

login_max_processes_count: 450

mail_location: maildir:/home/%1u/%u/Maildir

maildir_copy_with_hardlinks: yes

maildir_copy_preserve_filename: yes

mail_executable(default): /usr/local/libexec/dovecot/imap

mail_executable(imap): /usr/local/libexec/dovecot/imap

mail_executable(pop3): /usr/local/libexec/dovecot/pop3

mail_plugin_dir(default): /usr/local/lib/dovecot/imap

mail_plugin_dir(imap): /usr/local/lib/dovecot/imap

mail_plugin_dir(pop3): /usr/local/lib/dovecot/pop3

pop3_uidl_format(default):

pop3_uidl_format(imap):

pop3_uidl_format(pop3): %08Xu%08Xv

pop3_client_workarounds(default):

pop3_client_workarounds(imap):

pop3_client_workarounds(pop3): outlook-no-nuls oe-ns-eoh

auth default:

  count: 4

  passdb:

    driver: shadow

  userdb:

    driver: passwd

On Fri, 2009-08-07 at 10:03 -0400, P.A wrote:
> My  question is what do you guys think is happening here, what is the
> relationship between dovecot/postfix that would cause this to happen.
I'm
> just looking for some suggestions in case this happens again.
Does Postfix use Dovecot for SMTP AUTH? That's the only connection
between them..
> login_processes_count: 55
> 
> login_max_processes_count: 450
You could instead try:

login_process_per_connection = yes
login_processes_count = 2 # or the number of CPUs on your system
login_max_connections = 512 # or whatever you need for your max. load

http://wiki.dovecot.org/LoginProcess explains these things.

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On Fri, 2009-08-07 at 10:03 -0400, P.A wrote:
> # 1.0.10: /usr/local/etc/dovecot.conf
Oh, and upgrading Dovecot to v1.1 or v1.2 wouldn't hurt either. Who
knows, might even fix the problem for some reason.

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