[Dovecot] POP3 error

[Thierry de Montaudry]

Hi,

Since we upgraded to 2.0.9 (from 1.10 stock CentOS release), we are getting some errors with pop3. When the machines get busy, now and then it start with the following:
> Mar  7 11:19:51 xxx dovecot: pop3-login: Error: net_connect_unix(pop3) failed: Resource temporarily unavailable
And it generates hundreds of those before the machines dies, with the web server getting stuck as well on imap sessions, even though there is no imap error messages.

I tried to lookup in the source where this is generated, but couldn't find it. Is it some resource limit on the machine?

Please see bellow the dovecot -n output.

Regards,

	Thierry

# 2.0.9: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.18-194.32.1.el5 x86_64 CentOS release 5.5 (Final) nfs
auth_cache_negative_ttl = 0
auth_cache_size = 2 M
auth_cache_ttl = 10 mins
auth_mechanisms = plain login
dict {
 expire = mysql:/etc/dovecot/dovecot-dict-expire.conf.ext
 quota = mysql:/etc/dovecot/dovecot-dict-sql.conf.ext
}
disable_plaintext_auth = no
first_valid_uid = 25
lda_mailbox_autocreate = yes
lda_mailbox_autosubscribe = yes
mail_access_groups = vmail
mail_fsync = always
mail_gid = 25
mail_location = maildir:/var/virtual/%d/%1n/%2n/%n:INDEX=/var/indexes/%d/%1n/%2n/%n
mail_nfs_index = yes
mail_nfs_storage = yes
mail_plugins = quota expire
mail_uid = 25
mbox_write_locks = fcntl
mmap_disable = yes
passdb {
 args = /etc/dovecot/dovecot-sql.conf.ext
 driver = sql
}
plugin {
 expire = Trash
 expire2 = Trash/*
 expire3 = Spam
 expire4 = Trash/*
 expire_dict = proxy::expire
 quota = dict:User quota::proxy::quota
 quota_rule = *:storage=2G
 quota_rule2 = Trash:storage=+100M
 sieve_global_path = /var/indexes/dovecot-default.sieve
}
postmaster_address = postmaster at XXXXXX.YY
protocols = imap pop3
service auth {
 unix_listener auth-userdb {
   group = vmail
   mode = 0600
   user = vmail
 }
}
service dict {
 unix_listener dict {
   group = vmail
   mode = 0600
   user = vmail
 }
}
service imap-login {
 inet_listener imap {
   address = 127.0.0.1
   port = 143
 }
 process_min_avail = 2
 service_count = 0
 vsz_limit = 256 M
}
service imap {
 process_limit = 768
}
service pop3-login {
 inet_listener pop3 {
   address = 0.0.0.0
   port = 110
 }
 process_limit = 200
 process_min_avail = 2
 service_count = 0
}
service pop3 {
 process_limit = 256
}
ssl = no
ssl_cert = </etc/pki/dovecot/certs/dovecot.pem
ssl_key = </etc/pki/dovecot/private/dovecot.pem
userdb {
 driver = prefetch
}
userdb {
 args = /etc/dovecot/dovecot-sql.conf.ext
 driver = sql
}
userdb {
 args = uid=vmail gid=vmail
 driver = static
}
protocol lmtp {
 mail_plugins = quota expire sieve
}
protocol lda {
 mail_plugins = quota expire sieve
}
protocol imap {
 mail_plugins = quota expire imap_quota
}
protocol pop3 {
 mail_max_userip_connections = 2
 pop3_fast_size_lookups = yes
}