Compile:

erlc mod_prometheus.erl

Copy compiled file to ejabberd, for example:

cp mod_prometheus.beam /opt/ejabberd-17.07/lib/ejabberd-17.07/ebin/

Add config to ejabberd.yml:

listen:
 -
 port: 8181
 module: ejabberd_http
 request_handlers:
 "/metrics": mod_prometheus

After this, restart ejabberd and try open http://localhost:8181/metrics in browser. You have to see metrics for prometheus.

Service will responde all requests independently request type and request path.