OpenBSD | Too many open files

Do at runtime

 sysctl kern.maxfiles=10240

Burn it to the system:

Add a line kern.maxfiles=102400 to /etc/sysctl.conf.

Then tune /etc/login.conf:
Modify openfiles-max and openfiles-cur like
openfiles-max=102400
openfiles-cur=102400

Restart your process.