Converts the output of the NGINX stub_status module to Prometheus format so that basic metrics can be scraped from a /metrics endpoint.
The NGINX JavaScript module is used to filter the stub_status response.
$ curl -i http://localhost:8080/metrics
HTTP/1.1 200 OK
Server: nginx/1.21.3
Date: Thu, 21 Oct 2021 10:41:50 GMT
Content-Type: text/plain
Transfer-Encoding: chunked
Connection: keep-alive
connections{active} 1
connections{reading} 0
connections{writing} 1
connections{waiting} 0
server{accepts} 29
server{handled} 29
server{requests} 29