Nginx

The web server and reverse proxy: active and waiting connections, the accept/handled/request rates, and upstream health when the commercial NGINX Plus API is available.

Network ports to open

From the DumbMonit server (or its relay agent) to the device:

Port	Protocol	Purpose
80	TCP	Status page (HTTP, default)
443	TCP	Only if the status page is served over HTTPS

DumbMonit reads Nginx’s built-in stub_status module, a handful of plain-text counters, with no API and no account needed on a correctly filtered network. When the commercial NGINX Plus is installed, DumbMonit can also read its JSON API for upstream health and per-zone counters.

What it watches

All metrics are prefixed dumbmonit_nginx_. The _total metrics are counters: charts and rules turn them into rates.

Metric	What	Labels
connections_active	connections currently open
connections_reading, connections_writing, connections_waiting	connections by what they are doing
accepts_total, handled_total	connections accepted, and actually handled
requests_total	requests served since Nginx started
version_info	presence; the Server response header, when Nginx sends one	server
plus_upstream_server_up	1 when NGINX Plus marks the server up	upstream, server
plus_upstream_server_active, plus_upstream_server_requests_total, plus_upstream_server_fails_total, plus_upstream_server_5xx_total	NGINX Plus per-server counters	upstream, server
plus_zone_requests_total, plus_zone_5xx_total, plus_zone_received_bytes_total, plus_zone_sent_bytes_total	NGINX Plus per-zone counters	zone

A gap between accepts_total and handled_total means connections Nginx dropped before it could serve them (usually worker_connections reached). The plus_* metrics only appear when “Read the NGINX Plus API” is ticked and NGINX Plus answers; the open-source build does not have an “upstream” to report on stub_status alone.

The monitor page

The panel above the charts reads what the probe stored; opening the page never queries Nginx. It shows active, reading, writing and waiting connections, the accept/handled/request rates over 24 hours, and, with NGINX Plus, upstream health and per-zone traffic.

Enable Nginx’s stub_status module

1. Add this location to the server block Nginx already serves, restricted to the DumbMonit host (adjust the address).

   location /basic_status {
   stub_status;
   allow 10.0.0.5;
   deny all;
   }

2. Reload Nginx.

   nginx -s reload

3. Open http://nginx.lan/basic_status from the DumbMonit host: it must show Active connections.

4. In DumbMonit, enter the Nginx host, for example nginx.lan, and the path if it is not /basic_status.

5. If NGINX Plus is installed, tick Read the NGINX Plus API to add upstream health and per-zone counters.

Warning

stub_status only counts connections and requests: a configuration error in a server block or an unreachable backend does not show there.

Good to know

Nginx ships stub_status built in: it only needs a location that turns it on, in the server block Nginx already serves or in a server block of its own on another port. The allow and deny lines restrict it to the DumbMonit host, so no one else can read it. The open-source build has no notion of upstream: that only exists in NGINX Plus, read through its own API when enabled.

Vendor documentation: https://nginx.org/en/docs/http/ngx_http_stub_status_module.html

Credentials

Credential	Fields
No password	Nothing: the status page is filtered so that only DumbMonit reaches it.
Basic auth	The user and password of the block protecting the status page, if any.

Address: a host name or IP, with the port if it is not 80. Options: protocol (HTTP by default), port, status path (/basic_status by default), certificate check, request timeout (10 s), and the NGINX Plus API switch and version.