nginx: add missing doc for env vars

content/docs/howto/web-servers.md

@@ -204,6 +204,16 @@ files to `/workspace/my-build-directory`.
 BP_WEB_SERVER_ROOT=htdocs
 {{< /code/copyable >}}
 
+#### Set Location Path for the Server
+In auto-generated `nginx.conf`, the
+[`server.location`](https://nginx.org/en/docs/http/ngx_http_core_module.html#location)
+directive is set to the catch-all or default location block. You can override
+this by setting the `BP_WEB_SERVER_LOCATION_PATH` variable.
+
+{{< code/copyable >}}
+BP_WEB_SERVER_LOCATION_PATH="/custom"
+{{< /code/copyable >}}
+
 #### Enable Push-State Routing
 The `BP_WEB_SERVER_ENABLE_PUSH_STATE` variable enables push state routing
 functionality. This is useful for single-page web applications.
@@ -221,6 +231,21 @@ endpoint.
 BP_WEB_SERVER_FORCE_HTTPS=true
 {{< /code/copyable >}}
 
+#### Obtain real-time status info
+The `BP_NGINX_STUB_STATUS_PORT` variable exposes a handful of NGINX Server
+metrics via the
+[`stub_status`](https://nginx.org/en/docs/http/ngx_http_stub_status_module.html#stub_status)
+module which provides basic status information on provided port. This comes
+handy for monitoring the server. For example using [NGINX Prometheus
+Exporter](https://github.com/nginxinc/nginx-prometheus-exporter)
+
+The info will be made available at the path `/stub_status` at the specified
+port. Make sure that this port isn't used anywhere else in your application.
+
+{{< code/copyable >}}
+BP_NGINX_STUB_STATUS_PORT=8083
+{{< /code/copyable >}}
+
 #### Set Up Basic Authentication
 You are able to provide basic authentication credentials via a [service
 binding][service-binding] of type `htpasswd` that specifies the contents of a

content/docs/reference/nginx-reference.md

@@ -36,13 +36,19 @@ Defaults to `public`, setting this allows you to modify the location of the
 static files served by the web server with either an absolute file path or a
 file path relative to `/workspace`.
 
+### BP_WEB_SERVER_LOCATION_PATH
+Set server's location directive.
+
 ### BP_WEB_SERVER_ENABLE_PUSH_STATE
 Enables push state routing functionality.
 
 ### BP_WEB_SERVER_FORCE_HTTPS
 Allows you to enforce HTTPS for server connections by redirecting all requests
 to use the HTTPS protocol.
 
+### BP_NGINX_STUB_STATUS_PORT
+Gets NGINX basic status info via [`stub_status`](https://nginx.org/en/docs/http/ngx_http_stub_status_module.html#stub_status).
+
 ## Supported Service Bindings
 The NGINX buildpack can be configured using [service bindings][service-binding].
 ####