Frequent Out of Memory for service(config)

[Aki Tuomi]

On 13.5.2019 22.56, Root Kev via dovecot wrote:
> Hello Group,
>
> We have dovecot deployed as solely a Pop3 service that is used by our
> applications to pass mail from one application to another internally. 
> We have roughly 4 applications that connect to the Pop3 service every
> 2 seconds, to check for new messages and pop them for processing if
> they are present.  Depending on the site, we have between 1024-2048MB
> of memory set for default_vsz_limit.  In all systems we see the Out of
> memory alert several times a day. We previously did not see this at
> all when running on CentOS6, with less memory.
>
> We have tried increasing the memory to the vsz_limit up to 2gb without
> success. 
>
> We are running on CentOS 7 servers, running dovecot 2.3.6 (7eab80676)
> (from the dovecot repo).
>
> Can anyone advise any other settings that could be modified in order
> to correct these out of memory issues?
>
> # dovecot -n
> # 2.3.6 (7eab80676): /etc/dovecot/dovecot.conf
> # OS: Linux 3.10.0-957.5.1.el7.x86_64 x86_64 CentOS Linux release
> 7.6.1810 (Core) 
> # Hostname: ****** #<modified for security>
> auth_cache_size = 10 M
> auth_verbose = yes
> default_vsz_limit = 1 G
> instance_name = Pop3 Mail Service
> listen = 10.*.*.* #<modified for security>
> log_path = /var/log/dovecot.log
> login_greeting = Pop3 Mail Service
> login_trusted_networks = 10.*.*.* 10.*.*.* 10.*.*.* 10.*.*.* 10.*.*.*
> #<modified for security>
> mail_location = maildir:~/Maildir
> namespace inbox {
>   inbox = yes
>   location =
>   mailbox Drafts {
>     special_use = \Drafts
>   }
>   mailbox Junk {
>     special_use = \Junk
>   }
>   mailbox Sent {
>     special_use = \Sent
>   }
>   mailbox "Sent Messages" {
>     special_use = \Sent
>   }
>   mailbox Trash {
>     special_use = \Trash
>   }
>   prefix =
> }
> passdb {
>   args = cache_key=#hidden_use-P_to_show#
>   driver = pam
> }
> protocols = pop3
> ssl_cert = </etc/pki/dovecot/certs/dovecot.pem
> ssl_key = # hidden, use -P to show it
> userdb {
>   driver = passwd
> }
> verbose_ssl = yes
>
> May 10 06:44:05 config: Fatal: pool_system_malloc(8192): Out of memory
> May 10 06:44:05 config: Fatal: master: service(config): child 27887
> returned error 83 (Out of memory (service config { vsz_limit=1024 MB
> }, you may need to increase it) - set CORE_OUTOFMEM=1 environment to
> get core dump)

Can you try setting

import_environment = $import_environment CORE_OUTOFMEM=1

and see if it causes coredump?

Aki