README.md

Rack example

A simple Rack application which shows how to use prometheus' Rack::Exporter and Rack::Collector rack middlwares.

Run the example

Standalone

Execute the provided run script:

bundle install
bundle exec ./run

This will start the rack app, run a few requests against it, print the output of /metrics and terminate.

With a Prometheus server

Start a Prometheus server with the provided config:

prometheus -config.file ./prometheus.yaml

In another terminal, start the application server:

bundle install
bundle exec unicorn -c ./unicorn.conf

You can now open the example app and its metrics page to inspect the output. The running Prometheus server can be used to play around with the metrics.

Collector

The example shown in config.ru is a trivial rack application using the default collector and exporter middlewares.

In order to use a custom label builder in the collector, change the line to something like this:

use Prometheus::Client::Rack::Collector do |env|
  {
    method:       env['REQUEST_METHOD'].downcase,
    host:         env['HTTP_HOST'].to_s,
    path:         env['PATH_INFO'].to_s,
    http_version: env['HTTP_VERSION'].to_s,
  }
end