cannot login to imap under load - SOLVED

[Gerard Ranke]

On 29-03-17 14:40, Marcus Rueckert wrote:
> On 2017-03-29 13:33:52 +0200, Piper Andreas wrote:
>>> It does indeed run from systemd, so this is what's currently in the
>>> dovecot unit file ( /etc/systemd/system/dovecot.service ):
>>>
>> ...
>>> [Service]
>>> Type=simple
>>> ExecStart=/usr/sbin/dovecot -F
>>> NonBlocking=yes
>>> TasksMax=10000
>>> LIMIT_NOFILE=10000
>>
>> ...
>>
>> the parameter should be named
>>
>> LimitNOFile=10000
>>
>> (without the underscore), see
>> http://man7.org/linux/man-pages/man7/systemd.directives.7.html and
>> http://man7.org/linux/man-pages/man5/systemd.exec.5.html
> 
> Also you dont have to replace the whole service file to achieve this:
> 
> https://discourse.nordisch.org/t/per-service-ulimits/374
> 
>    darix
> 

Good point! I did remove the /etc/systemd/system/docevot.service file
and added /etc/systemd/system/dovecot.service.d/limits.conf which reads:

[Service]
TasksMax=10000
LimitNOFILE=10000

This should survive system upgrades as well.
( The TaskMax setting is to overcome the default 512 from a cgroup
controller that is new for sles12sp2. )

After that it also needed:
systemctl daemon-reload
systemctl restart dovecot

Now dovecot starts up cleanly, and our performance problems are gone.
Thank you all who took the time to answer, your remarks were very
supporting and insightful! It's just what you need when you have a lot
of users breathing down your neck :-)
All the best!

gerard