[Dovecot] Connection queue full on dovecot 1.1.14 and 1.1.15

[Sven Eulberg]

Hello,

sometimes we get the following errors on out dovecot proxies:

dovecot: May 27 20:06:10 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS handshaking
dovecot: May 27 20:06:10 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS handshaking
dovecot: May 27 20:06:10 Info: imap-login: Disconnected: Connection  
queue full (auth failed, 1 attempts): user=<USER>, method=PLAIN,  
REMOTE=<IP> LOCAL=<IP>
dovecot: May 27 20:06:10 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS handshaking
dovecot: May 27 20:06:10 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS handshaking
dovecot: May 27 20:06:10 Info: imap-login: Disconnected: Connection  
queue full (auth failed, 1 attempts): user=<USER>, method=PLAIN,  
REMOTE=<IP> LOCAL=<IP>
dovecot: May 27 20:06:10 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS handshaking
dovecot: May 27 20:06:10 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS
dovecot: May 27 20:06:11 Info: imap-login: Disconnected: Connection  
queue full (auth failed, 1 attempts): user=<USER>, method=PLAIN,  
REMOTE=<IP> LOCAL=<IP> TLS
dovecot: May 27 20:06:12 Info: imap-login: Disconnected: Connection  
queue full (auth failed, 1 attempts): user=<USER>, method=PLAIN,  
REMOTE=<IP> LOCAL=<IP> TLS
dovecot: May 27 20:06:15 Info: imap-login: Disconnected: Connection  
queue full (auth failed, 1 attempts): user=<USER>, method=PLAIN,  
REMOTE=<IP> LOCAL=<IP>
dovecot: May 27 20:09:36 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS
dovecot: May 27 20:09:36 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP>
dovecot: May 27 20:09:36 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS handshaking
dovecot: May 27 20:09:36 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS handshaking
dovecot: May 27 20:09:36 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS handshaking
dovecot: May 27 20:11:18 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS
dovecot: May 27 20:11:18 Info: imap-login: Disconnected: Connection  
queue full (auth failed, 1 attempts): user=<USER>, method=PLAIN,  
REMOTE=<IP> LOCAL=<IP> TLS
dovecot: May 27 20:39:22 Info: imap-login: Disconnected: Connection  
queue full (no auth attempts): REMOTE=<IP> LOCAL=<IP> TLS handshaking
dovecot: May 27 20:39:22 Info: imap-login: Disconnected: Connection  
queue full (auth failed, 1 attempts): user=<USER>, method=PLAIN,  
REMOTE=<IP> LOCAL=<IP> TLS
dovecot: May 27 20:39:23 Info: imap-login: Disconnected: Connection  
queue full (auth failed, 1 attempts): user=<USER>, method=PLAIN,  
REMOTE=<IP> LOCAL=<IP>

Our config:

./dovecot -n
# 1.1.15: /usr/local/dovecot-1.1.15/etc/dovecot.conf
# OS: Linux 2.6.18-6-686 i686 Debian 4.0
base_dir: /usr/local/dovecot/var/run/dovecot/
log_path: /var/log/dovecot-1.1.log
protocols: pop3 pop3s imap imaps
ssl_ca_file: /usr/local/dovecot/etc/ssl/de.TR_CRT
ssl_cert_file: /usr/local/dovecot/etc/ssl/de.CRT
ssl_key_file: /usr/local/dovecot/etc/ssl/de.PKEY
disable_plaintext_auth: no
login_dir: /usr/local/dovecot/var/run/dovecot/login
login_executable(default): /usr/local/dovecot-1.1.15/libexec/dovecot/ 
imap-login
login_executable(imap): /usr/local/dovecot-1.1.15/libexec/dovecot/imap- 
login
login_executable(pop3): /usr/local/dovecot-1.1.15/libexec/dovecot/pop3- 
login
login_log_format_elements: user=<%u> method=%m REMOTE=%r LOCAL=%l %c
login_process_per_connection: no
login_greeting_capability(default): yes
login_greeting_capability(imap): yes
login_greeting_capability(pop3): no
login_processes_count: 10
login_max_processes_count: 256
verbose_proctitle: yes
mail_location: maildir:/home/email/%u/Maildir
mailbox_idle_check_interval: 60
mmap_disable: yes
fsync_disable: yes
mail_executable(default): /usr/local/dovecot-1.1.15/libexec/dovecot/imap
mail_executable(imap): /usr/local/dovecot-1.1.15/libexec/dovecot/imap
mail_executable(pop3): /usr/local/dovecot-1.1.15/libexec/dovecot/pop3
mail_process_size: 512
mail_plugins(default): quota imap_quota
mail_plugins(imap): quota imap_quota
mail_plugins(pop3): quota
mail_plugin_dir(default): /usr/local/dovecot-1.1.15/lib/dovecot/imap
mail_plugin_dir(imap): /usr/local/dovecot-1.1.15/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/local/dovecot-1.1.15/lib/dovecot/pop3
imap_client_workarounds(default): delay-newmail outlook-idle netscape- 
eoh tb-extra-mailbox-sep
imap_client_workarounds(imap): delay-newmail outlook-idle netscape-eoh  
tb-extra-mailbox-sep
imap_client_workarounds(pop3):
pop3_lock_session(default): no
pop3_lock_session(imap): no
pop3_lock_session(pop3): yes
pop3_uidl_format(default): %08Xu%08Xv
pop3_uidl_format(imap): %08Xu%08Xv
pop3_uidl_format(pop3): %v.%u
pop3_client_workarounds(default):
pop3_client_workarounds(imap):
pop3_client_workarounds(pop3): outlook-no-nuls oe-ns-eoh
auth default:
  mechanisms: plain login
  cache_size: 1024
  cache_ttl: 28800
  failure_delay: 3
  passdb:
    driver: sql
    args: /usr/local/dovecot/etc/dovecot-mysql.conf


It seems to me the error occurs more often after increasing  
login_processes_count.
This errors exists with version 1.1.14 and 1.1.15 and I guess also in  
earlier versions.

Thanks in advance!

Best regards,
Sven