Nginx failed (24: Too many open files)

[Haw Loeung]

Hi,

On a heavily loaded server, we're seeing Nginx spewing too many open files for both accessing files on disk as well as for TCP connections:

| 2021/11/22 22:58:12 [crit] 17293#17293: *154644983 open() "/var/lib/nginx/proxy/XXX/d/de/YYY" failed (24: Too many open files), client: 127.0.0.1, server: XXX, request: "GET /_status/ping HTTP/1.0", host: "XXX"
| 2021/11/22 23:03:24 [crit] 17293#17293: accept4() failed (24: Too many open files)

It uses the system default limits:

| $ for i in $(pidof nginx); do sudo cat /proc/$i/limits | grep open; done
| Max open files 1024 4096 files
| Max open files 1024 4096 files
| ...

Adding "worker_rlimit_nofile 8192;" to /etc/nginx/nginx.conf helps bump this up:

| $ for i in $(pidof nginx); do sudo cat /proc/$i/limits | grep open; done
| Max open files 8192 8192 files
| Max open files 8192 8192 files

We should fix the charm to bump this and make it configurable / automatically calculated.