[Dovecot] Dovecot Director Output buffer full

[Dominic Malolepszy]

Hi,

I have been seeing the following messages in logs on all my Dovecot 
servers each running both a dovecot-director instance and a dovecot 
pop3/imap backend. These logs appear to relate to problems with the 
director.

Aug 28 16:09:52 dovecot01 dovecot: director: Error: 
director(10.0.0.2:9090/right): Output buffer full, disconnecting
Aug 28 16:10:01 dovecot01 dovecot: director: Error: Ring SYNC appears to 
have got lost, resending
Aug 28 16:10:02 dovecot01 dovecot: director: Error: Director 
10.0.0.2:9090/right disconnected

Aug 28 16:09:51 dovecot02 dovecot: director: Error: 
director(10.0.0.3:9090/right): Output buffer full, disconnecting
Aug 28 16:09:57 dovecot02 dovecot: director: Error: Ring SYNC appears to 
have got lost, resending
Aug 28 16:10:01 dovecot02 dovecot: director: Error: Director 
10.0.0.3:9090/right disconnected
Aug 28 16:10:02 dovecot02 dovecot: director: Error: 
director(10.0.0.1:9090/left): Ping timed out, disconnecting
Aug 28 16:13:15 dovecot02 dovecot: director: Warning: Delaying new user 
requests until ring is synced

Note dovecot01 has IP 10.0.0.1 and dovecot02 has IP 10.0.0.2 and so on.

This seems to show up when I enable the poolmon script 
(https://github.com/brandond/poolmon) on all the servers, and all 
servers start simultaneous logins to each others Dovecot backends. I did 
notice that the poolmon script has been flapping vhost weights a lot (I 
am looking at making the script handle transient errors better), which 
means that it is connecting to the dovecot-director socket every few 
minutes and changing vhost weights from 100 to 0 and vice-versa. Is 
there some sort of limit in the Dovecot Director that is being exceeded 
that should be tweaked?


# 2.1.5: /etc/dovecot-director/dovecot.conf
# OS: Linux 2.6.32-279.el6.mccqfix.x86_64 x86_64 Red Hat Enterprise 
Linux Server release 6.3 (Santiago)
auth_cache_size = 100 M
auth_default_realm = example.com
auth_failure_delay = 5 secs
auth_mechanisms = plain login
auth_verbose = yes
auth_verbose_passwords = sha1
auth_worker_max_count = 600
base_dir = /var/run/dovecot-director/
director_mail_servers = 10.0.0.1 10.0.0.2 10.0.0.3 10.0.0.4 10.0.0.5
director_servers = 10.0.0.1 10.0.0.2 10.0.0.3 10.0.0.4 10.0.0.5
disable_plaintext_auth = no
instance_name = dovecot-dir
passdb {
   args = /etc/dovecot-director/dovecot-sql.conf
   driver = sql
}
service director {
   fifo_listener login/proxy-notify {
     mode = 0666
   }
   inet_listener {
     address = 10.0.0.1
     port = 9090
   }
   unix_listener director-userdb {
     mode = 0600
   }
   unix_listener login/director {
     mode = 0666
   }
}
service imap-login {
   executable = imap-login director
   inet_listener imap {
     address = 10.0.0.1
     port = 143
   }
   inet_listener imaps {
     address = 10.0.0.1
     port = 993
     ssl = yes
   }
   process_min_avail = 100
}
service pop3-login {
   executable = pop3-login director
   inet_listener pop3 {
     address = 10.0.0.1
     port = 110
   }
   inet_listener pop3s {
     address = 10.0.0.1
     port = 995
     ssl = yes
   }
   process_min_avail = 100
}
verbose_proctitle = yes