Fly.io Prometheus Metrics

An example repository showing how to instrument a Laravel application, so it creates Prometheus metrics.

There are a few elements:

1. Creates a /metrics endpoint for Prometheus to scrape
2. Stores metrics in Redis so they persist long enough for Prometheus to get when periodically calling the /metrics endpoint
3. Generates user (programmer) defined metrics

The Code

In this specific repository, we use the promphp/prometheus_client_php composer package in Laravel.

Files to check out:

1. app/Providers/PrometheusServiceProvider - registered in config/app.php, creates a singleton for the Prometheus library CollectorRegistry class (the main one you use for that library)
   • Also sets up Redis to persist metrics
2. app/Prometheus - classes corresponding to metrics created in the app, along with the Prom facade
3. app/Http/Controllers/Metrics.php - The controller that generates metrics output for Prometheus to read at the /metrics route, registered in routes/web.php
4. app/Console/Commands/GenerateMetricsCommand.php - A console command, called every few minutes by the scheduler. This generate some metrics with some randomness, simulating what might be real-ish metrics.

The metrics this app collects is related to the corresponding article found at https://fly.io/laravel-bytes.