[Samba] winbind file open limits

[Nate Collins]

We have monitoring in place to detect when processes on servers are
approaching their open file limits (ulimit -n). On all our Ubuntu servers,
winbind processes have a soft limit of 270 (this seems to be the default),
and most winbind processes use up most or all of these open files. We've
been noticing some domain join flakiness on some of our servers, and
are trying to determine if processes reaching their soft file limit is
related or not.

I attempted to increase the open file limits for winbind via LimitNOFILE
in systemd, and was able to set the hard limit, but not the soft limit:

# systemctl show --property MainPID --value winbind
6194
# cat /proc/6194/limits | grep 'open files'
Max open files            270                  524288               files
# vim /etc/systemd/system/winbind.service.d/override.conf
# cat /etc/systemd/system/winbind.service.d/override.conf | grep LimitNOFILE
LimitNOFILE=2048:524287
# systemctl daemon-reload
# systemctl restart winbind
# systemctl show --property MainPID --value winbind
6269
# cat /proc/6269/limits | grep 'open files'
Max open files            270                  524287               files
#

Does winbind adjust the soft limit on process initialization, or is there
something else at play? Should we be concerned about winbind processes
reaching their soft file limits?

Thanks,
Nate