confusing nginx.conf docs example; use both ngx_http_subs_filter_module and ngx_http_sub_module

[jtmoon79]

tl;dr docs allude to two different nginx modules ngx_http_subs_filter_module and ngx_http_sub_module.

The documentation example nginx.conf is

server {
    listen gerbera.DOMAINNAME:80;
    server_name gerbera.DOMAINNAME;

    location / {
        proxy_set_header   Host               $host;
        proxy_set_header   X-Real-IP          $remote_addr;
        proxy_set_header   X-Forwarded-For    $proxy_add_x_forwarded_for;
        proxy_set_header   X-Forwarded-Host   $host:$server_port;
        proxy_set_header   X-Forwarded-Server $host;

        # install sub filter module and enable in nginx.conf
        # load_module /usr/lib64/nginx/modules/ngx_http_subs_filter_module.so;
        sub_filter_once    off;
        sub_filter_types   text/html application/json;
        sub_filter         'http://GERBERA_IP:GERBERA_PORT' 'http://$host:$server_port';

        proxy_pass         http://GERBERA_IP:GERBERA_PORT/;
    }
}

ngx_http_sub_module

The directive sub_filter_once is from nginx module ngx_http_sub_module.
However, those directives failed for me

$ service nginx restart; systemctl status nginx.service
...
unknown directive "sub_filter_once" in /etc/nginx/sites-enabled/gerbera:15

(I have installed apt packages nginx-common nginx-light on a recent Debian)

ngx_http_subs_filter_module

Looking at the example again, it refers to

# load_module /usr/lib64/nginx/modules/ngx_http_subs_filter_module.so;

I was able to install via apt install libnginx-mod-http-subs-filter.

That refers to ngx_http_substitutions_filter_module.
That modules documentation does not have sub_filter_once directive.
Instead, it has similar (but not the same) directives subs_filter_types and subs_filter.

I manually changed the nginx.conf directives to:

subs_filter_types   text/html application/json;
subs_filter         'http://gerbera.myhost.local:80' 'http://$host:$server_port';

However, this resulted in a HTTP 500 error (tested using curl -v http://gerbera.myhost.local).

different modules!

It appears there was some divergence or overlap of similarly-named nginx modules ngx_http_subs_filter_module and ngx_http_sub_module.

Could a gerbera expert clarify the nginx.conf example in the docs?

gerbera was installed using apt, version 1.1.0.

[KarlStraussberger]

I have the following modules loaded in my nginx.conf:

load_module /usr/lib64/nginx/modules/ngx_http_headers_more_filter_module.so;
load_module /usr/lib64/nginx/modules/ngx_http_subs_filter_module.so;

and the example was just copied from vhosts.d/

This config was tested for something like gerbera 1.6. Older versions may not work as described. So you'd better try to get something newer.