[Dovecot] Dovecot stops talking to the auth server.

[Tom Diehl]

Hi,

I have an RHEL4 machine running dovecot-1.0.3 + postfix-2.3.2 + 
postfixadmin + mysql-4.1.20-2.RHEL4.1 + amavisd-new-2.5.2-1.

The machine only has a gig of memory in it, I am trying to keep it
running until I get new hardware to replace it in a couple of weeks.

For the most part it works as advertised but every once in a while it
stops talking to the auth server. I think I have tracked this to periods
of high auth requests. Today the machine experienced a dictionary attack and
I had log entries like the following:

Sep 10 13:31:06 rocky dovecot: pop3-login: Disconnected: Shutting down: rip=::ffff:24.0.201.240, lip=::ffff:192.168.0.16
Sep 10 13:31:06 rocky dovecot: pop3-login: Can't connect to auth server at default: Resource temporarily unavailable
Sep 10 13:31:07 rocky last message repeated 47 times
Sep 10 13:31:08 rocky dovecot: pop3-login: Disconnected: Shutting down: rip=::ffff:24.0.201.240, lip=::ffff:192.168.0.16
Sep 10 13:31:08 rocky dovecot: imap-login: Can't connect to auth server at default: Resource temporarily unavailable
Sep 10 13:31:08 rocky dovecot: pop3-login: Can't connect to auth server at default: Resource temporarily unavailable
Sep 10 13:31:09 rocky last message repeated 27 times
Sep 10 13:31:09 rocky dovecot: imap-login: Can't connect to auth server at default: Resource temporarily unavailable
Sep 10 13:31:09 rocky dovecot: pop3-login: Can't connect to auth server at default: Resource temporarily unavailable
Sep 10 13:31:09 rocky last message repeated 4 times
Sep 10 13:31:09 rocky dovecot: imap-login: Can't connect to auth server at default: Resource temporarily unavailable
...

a ps showed numerous defunct processes similar to the following:

...
nobody   16647  0.0  0.2  9784 2112 ?        S    13:17   0:00 dovecot-auth
nobody   16654  0.0  0.2  9784 2088 ?        S    13:17   0:00 dovecot-auth
nobody   16663  0.0  0.0     0    0 ?        Z    13:17   0:00 [dovecot-auth] <defunct>
nobody   16668  0.0  0.2  9784 2088 ?        S    13:17   0:00 dovecot-auth
nobody   16669  0.0  0.0     0    0 ?        Z    13:17   0:00 [dovecot-auth] <defunct>
nobody   16671  0.0  0.2  9784 2088 ?        S    13:17   0:00 dovecot-auth
nobody   16672  0.0  0.2  9784 2128 ?        S    13:17   0:00 dovecot-auth
nobody   16673  0.0  0.2  9784 2088 ?        S    13:17   0:00 dovecot-auth
nobody   16674  0.0  0.2  9784 2088 ?        S    13:17   0:00 dovecot-auth
nobody   16675  0.0  0.2  9784 2112 ?        S    13:17   0:00 dovecot-auth
nobody   16681  0.0  0.0     0    0 ?        Z    13:17   0:00 [dovecot-auth] <defunct>
...

dovecot -n follows:

(rocky pts4) # dovecot -n
# 1.0.3: /etc/dovecot.conf
login_dir: /var/run/dovecot/login
login_executable(default): /usr/libexec/dovecot/imap-login
login_executable(imap): /usr/libexec/dovecot/imap-login
login_executable(pop3): /usr/libexec/dovecot/pop3-login
first_valid_uid: 509
last_valid_uid: 509
first_valid_gid: 509
last_valid_gid: 509
mail_extra_groups: vmail
mail_location: maildir:~/
maildir_copy_with_hardlinks: yes
mail_executable(default): /usr/libexec/dovecot/imap
mail_executable(imap): /usr/libexec/dovecot/imap
mail_executable(pop3): /usr/libexec/dovecot/pop3
mail_plugins(default):
mail_plugins(imap):
mail_plugins(pop3): quota
mail_plugin_dir(default): /usr/lib/dovecot/imap
mail_plugin_dir(imap): /usr/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/pop3
imap_client_workarounds(default): outlook-idle delay-newmail
imap_client_workarounds(imap): outlook-idle delay-newmail
imap_client_workarounds(pop3): outlook-idle
pop3_client_workarounds(default):
pop3_client_workarounds(imap):
pop3_client_workarounds(pop3): outlook-no-nuls oe-ns-eoh
auth default:
   mechanisms: plain login
   user: nobody
   worker_max_count: 20
   passdb:
     driver: sql
     args: /etc/dovecot/sql.conf
   passdb:
     driver: pam
   userdb:
     driver: passwd
   userdb:
     driver: static
     args: uid=509 gid=509 home=/home/vmail/domains/%d/%n
   userdb:
     driver: sql
     args: /etc/dovecot/sql.conf
   userdb:
     driver: prefetch
   socket:
     type: listen
     client:
       path: /var/spool/postfix/private/auth
       mode: 432
       user: postfix
       group: vmail
     master:
       path: /var/run/dovecot/auth-master
       mode: 432
       user: vmail
       group: vmail
plugin:
   quota: maildir:storage=10240:messages=1000
   acl: vfile:/etc/dovecot/acls
   trash: /etc/dovecot/trash.conf
(rocky pts4) #

Is there anything I can do to prevent this? Does this look like simply a
resource problem or am I doing something else wrong?

Regards,

-- 
Tom Diehl		tdiehl at rogueind.com		Spamtrap address mtd123 at rogueind.com