[Dovecot] questions about process_limit

[Jiri Bourek]

Andreas Meyer wrote:
> Hello all!
>
> # dovecot --version
> 2.1.17
>
> Sometimes I have this in the logfile:
>
> May 11 16:55:52 master: Warning: service(imap-login): process_limit (100) reached, client connections are being dropped
> May 11 17:35:03 master: Warning: service(imap-login): process_limit (100) reached, client connections are being dropped
> May 11 17:36:27 master: Warning: service(imap-login): process_limit (100) reached, client connections are being dropped
>
> I then put this in the dovecot.conf
>
> service imap-login {
>    service_count = 1
>    process_min_avail = 50
>    #process_limit = $default_process_limit
>    process_limit = 10000
>    vsz_limit = 64M
> }
>
> and get this:
>
> May 11 18:19:36 master: Info: Dovecot v2.1.17 starting up (core dumps disabled)
> May 11 18:19:36 config: Warning: service auth { client_limit=1000 } is lower than required under max. load (10300)
> May 11 18:19:36 config: Warning: service anvil { client_limit=1000 } is lower than required under max. load (10203)
>
> Puting this in:
>
> service auth {
> client_limit = 10300
>      unix_listener auth-userdb {
>        mode = 0666
>        user = vmail
>        group = vmail
>      }
> }
>
> service anvil {
> client_limit = 10300
> }
>
> I get this:
>
> May 11 18:27:37 delta.bitcorner.eu dovecot[3989]: Warning: fd limit (ulimit -n) is lower than required under max. load (1024<  10300), because of service auth { client_limit }

I says that if Dovecot auth process tries to service all 10300 clients, 
it'll open too many file descriptors and run into a limit. In other 
words, you configured 10300 but it's not able to service more than 1000.

Try adding ulimit -n 32768 somewhere before Dovecot is executed (I put 
it into /etc/default/dovecot on Debian), that should clear the warning.

>
> I have also seen this today:
>
> May 11 13:14:05 log: Warning: Killed with signal 15 (by pid=1 uid=0 code=kill)
> May 11 13:14:05 auth: Error: read(anvil-auth-penalty) failed: EOF
> May 11 13:14:05 auth: Error: net_connect_unix(anvil-auth-penalty) failed: Permission denied
>

Signal 15 is TERM, it's used by init scripts to stop Dovecot. Those 
errors seem to me like a result of one process (auth) trying to 
communicate with another (anvil), which was already shutting down. 
Doesn't strike me as a problem (but I may be wrong ofc)