Monitoring Erlang Applications with Prometheus

Professional

You can instrument your Erlang application with deadtrickster/prometheus.erl and let the Glouton agent scrape its /metrics endpoint.

Install the client library

Add the dependencies to your rebar.config:

{deps, [
    {prometheus, "4.11.0"},
    {prometheus_httpd, "2.1.12"}
]}.

Minimal example

The snippet below defines a counter and exposes it on http://localhost:8081/metrics using the bundled HTTP exporter:

-module(myapp).
-export([start/0]).

start() ->
    {ok, _} = application:ensure_all_started(prometheus),
    {ok, _} = application:ensure_all_started(prometheus_httpd),

    prometheus_counter:declare([
        {name, myapp_requests_total},
        {help, "Total number of processed requests."}
    ]),
    prometheus_counter:inc(myapp_requests_total),

    prometheus_httpd:start([{port, 8081}]).

Scrape with Glouton

Configure Glouton to scrape your application by adding the following to /etc/glouton/conf.d/50-prometheus-metrics.conf:

metric:
  prometheus:
    targets:
      - url: "http://localhost:8081/metrics"
        name: "my_erlang_application"
        allow_metrics:
          - "myapp_requests_total"

Restart the agent to apply the configuration. See Prometheus Monitoring for the full list of options, including Docker label auto-discovery and Kubernetes annotations.