account.key and certificate files deleted from state_path with error

[dcava]

Bug Overview

account.key and certificate files are deleted from state_path a few minutes after nginx restart.

Expected Behavior

account.key and certificate files persist as state_path is correctly specified.

Steps to Reproduce the Bug

I've defined this block in nginx.conf:

    ##
    # ACME settings
    ##
   resolver 127.0.0.53;

   acme_issuer letsencrypt {
        uri         https://acme-v02.api.letsencrypt.org/directory;
        contact     postmaster@example.com;
        state_path  /var/cache/nginx/acme-letsencrypt;
        accept_terms_of_service;
    }

On restart, an account.key is created in state_path and certificates subsequently created and work normally. No errors on start.
After about 2-3 minutes the files are removed from state_path and the following error appears in the log:

2025/08/22 09:41:58 [crit] 4126722#4126722: cache file "/var/cache/nginx/acme-letsencrypt/example.com-9a49b2628af2593f.key" is too small
2025/08/22 09:41:58 [crit] 4126722#4126722: cache file "/var/cache/nginx/acme-letsencrypt/account.key" is too small

The site continues to work presumably due to the certificate in shared memory, but restarting nginx requests a new cert (which is going to hit rate limits quickly see #32).

I'm guessing the files are meant to remain in state_path?

Environment Details

Ubuntu noble
Nginx mainline/nginx-acme 1.29.1+0.1.1-1~noble (via apt)

Additional Context

No response

[bavshin-f5]

The files are meant to remain, yes. And the error logs point to a possible reason: one of the http file caches (configured with fastcgi_cache_path, proxy_cache_path, scgi_cache_path, uwsgi_cache_path) believes that it should manage /var/cache/nginx/ and any nested directories. By default, all these caches are initialized in subdirectories of /var/cache/nginx and are not supposed to interfere with the acme module state.

[dcava]

Many thanks. You are absolutely right - a mastodon instance had set

proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=CACHE:10m inactive=7d max_size=1g;

Which was running rough-shod over the whole cache dir. Stupid. Files persist as intended after fixing that.

Thanks again.