Problems with odoo and wkhtmltopdf in Kubernetes

We have several Odoo instances in several Kubernetes clusters at Digitalocean. This normally works without any problems.

With one customer we have a problem that we run into a limitation with the “max open files” when generating a large PDF with wkhtmltopdf.

The system returns the following error:

{"level": "WARNING", "time": "2025-06-16 21:06:31.400712Z", "msg": "ERROR while sending the delivery slips for CUSTOMER.\nWkhtmltopdf ist fehlgeschlagen (Fehlercode: -6). Nachricht: QEventDispatcherUNIXPrivate(): Unable to create thread pipe: Too many open files\nQEventDispatcherUNIXPrivate(): Can not continue without a thread pipe\n”}

(Unfortunately, we do not currently know how large the PDF is or how many files there are as it is executed in a job.)

Google and AI basically tell us that the limit for the “open files” is probably too low. So we tried to increase this limit.

But the limit is already absurdly high (1048576) in my eyes. In addition, I cannot increase it above the hard limit.

root@pros-69d849fd7-zwc6z:/# ulimit -aH
real-time non-blocking time  (microseconds, -R) unlimited
core file size              (blocks, -c) unlimited
data seg size               (kbytes, -d) unlimited
scheduling priority                 (-e) 0
file size                   (blocks, -f) unlimited
pending signals                     (-i) 31610
max locked memory           (kbytes, -l) 8192
max memory size             (kbytes, -m) unlimited
open files                          (-n) 1048576
pipe size                (512 bytes, -p) 8
POSIX message queues         (bytes, -q) 819200
real-time priority                  (-r) 0
stack size                  (kbytes, -s) unlimited
cpu time                   (seconds, -t) unlimited
max user processes                  (-u) unlimited
virtual memory              (kbytes, -v) unlimited
file locks                          (-x) unlimited

root@pros-69d849fd7-zwc6z:/# ulimit -n 2000000
bash: ulimit: open files: cannot modify limit: Operation not permitted

Is my assumption correct that we cannot increase the “hard limit” (nofile) in DigitalOcean’s managed kubernetes?

If anyone has an idea what else could be the problem, I am open to suggestions.

The container is an Ubuntu (Ubuntu 22.04.5 LTS x86_64) the default image of odoo.

Thanks in advance Marcel