On 08/01/2020 01:47, @lbutlr wrote:
On 07 Jan 2020, at 07:15, Dovecot Mailing List <dovecot@dovecot.org> wrote:
dovecot: master: Warning: service(imap-login): process_limit (16) reached, client connections are being dropped
Is this an actual problem? Most client connections are idle, so I doubt if the occasional drop is noticed at all.
I assume it would mean Dovecot is dropping new incoming connections (e.g. new users trying to log in), not existing idle connections? Dropping new incoming connections is a major problem, because some email clients (e.g. Outlook) are notorious for giving the users password prompts whenever something unexpected happens.
It is a problem because it is unexpected behaviour. Where are the imap-login sockets going, if not to serve active TCP connections? On all servers, the number total-available imap-login processes is significantly larger than the number of TCP connections on the server. In some cases, it is about
~# ss -nt | wc -l 7817 ~# ss -nt "( sport = :143 or sport = :993 )" | wc -l 7812 ~# doveadm process status | grep "^imap-login " imap-login 17384 1462 44553 0 1578475790 0 imap-login 17383 550 66830 0 1578475790 0 imap-login 17382 488 59074 0 1578475789 0 imap-login 17381 929 58251 0 1578475790 0 imap-login 17380 712 62790 0 1578475790 0 imap-login 17377 1608 35143 0 1578475790 0 imap-login 17376 1718 27955 0 1578475790 0 imap-login 17375 1880 14903 0 1578475789 0 imap-login 17374 1965 10754 0 1578475790 0 imap-login 17373 1796 21137 0 1578475790 0 imap-login 17372 1194 52360 0 1578475789 0 imap-login 17371 1994 7482 0 1578475790 0 imap-login 17370 2061 3793 0 1578475789 0 imap-login 17369 2127 2992 0 1578475789 0 imap-login 17368 2014 5152 0 1578475790 0 imap-login 17362 2144 2723 0 1578475787 0 ~# doveadm process status | grep "^imap-login " | awk "{sum += \$3} END {print 40000-sum}" 15385
Why is there a (growing) discrepancy between the number of active TCP connections, and the number of reported free imap-login sockets? Is something else using imap-login thr
Also, why a limit of 16? Have you tried, oh, 160 instead?
The limit was set to match the process_limit of the imap service (16*1250=20000).
We have made the assumption that imap-login should not require more sockets than the maximum number of concurrent imap sessions. We have not had any issues with this before upgrading, but it appears to not be the case in 2.3.x?
-- Eirik