Prometheus exporter

Any exporter that serves the Prometheus text format: node_exporter, windows_exporter, cAdvisor, blackbox_exporter, smartctl_exporter, a database exporter, or one you wrote. DumbMonit reads its /metrics page on every check and stores each series, so it shows up in the explorer and the graphs and can be used in threshold rules.

Network ports to open

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

Port	Protocol	Purpose
9100	TCP	Metrics page (HTTP, default for node_exporter)

Other exporters use their own port; the Exporter list fills in the usual one: windows_exporter 9182, cAdvisor 8080, blackbox_exporter 9115, snmp_exporter 9116, smartctl_exporter 9633, mysqld_exporter 9104, postgres_exporter 9187, redis_exporter 9121, nginx exporter 9113, Prometheus 9090.

Setup

1. Check that the exporter answers from the DumbMonit host.

   curl http://server.lan:9100/metrics

2. In DumbMonit, add a Prometheus exporter monitor, enter the host and pick the exporter (or leave custom and give the port).
3. Optional: restrict what is stored with Keep only or Ignore.
4. Optional: if the exporter is on another site, choose a relay agent to read it from there.

You can also paste the whole URL as the address, for example http://server.lan:9100/metrics or, for the blackbox exporter, http://bb.lan:9115/probe?target=example.org&module=http_2xx.

What it stores

Every series of the page is stored as dumbmonit_<name> with its own labels, plus target (the monitor) and host (its name). A label named target or host coming from the exporter is kept as exported_target or exported_host. Series declared counter (and the _bucket, _count, _sum of histograms and summaries) are stored as counters: graphs and rules turn them into rates with rate(). Everything else is a gauge. NaN and infinite values are not stored.

Two extra series tell how the read went:

Metric	What
scrape_series	Series stored by the last read.
scrape_series_dropped	Series left out because the limit was reached.

Options

Option	Default	Purpose
Exporter	custom	Preset for the port.
Protocol, Port	http, preset port	Where the exporter listens.
Path	/metrics	Page to read, with its query if any.
Keep only	empty	Regular expression: only the metrics whose name matches are stored.
Ignore	empty	Regular expression: the metrics whose name matches are not stored.
Series limit	5000	At most this many series per read (1 to 50000); the surplus is counted.
Accept an unverifiable certificate	off	For an HTTPS exporter with a private certificate.

Expressions are RE2-style (the Rust regex syntax), unanchored: write ^node_ to match a prefix. They apply to the metric name, after Keep only.

Authentication

None, a user name and password (HTTP basic) or a bearer token. Secrets are stored encrypted and never shown again.

Failures

An exporter that does not answer (connection refused, timeout, 5xx) marks the monitor down. A refused login (401, 403), a page that is not Prometheus metrics or a wrong path is a configuration problem: it is shown on the monitor but does not notify anyone.

Alerts

No rule is shipped, since the metrics depend on the exporter. Create a threshold rule on any series, for example 100 - avg by (target) (rate(dumbmonit_node_cpu_seconds_total{mode="idle"}[5m])) * 100 > 90 (see Alert rules).