Monitoring Elixir Apps on Fly.io With Prometheus and PromEx
Fly.io takes Docker containers and converts them into fleets of Firecracker micro-vms running in racks around the world. If you have a working Docker container, you can run it close to your users, whether they're in Singapore or Amsterdam, with just a couple of commands. Fly.io is particularly nice for Elixir applications, because Elixir's first-class support for distributed computing meshes perfectly with Fly.io's first-class support for clusters of applications.
This post is about another cool Fly.io feature --- built-in Prometheus metrics --- and how easy it is to take advantage of them in an Elixir application. I wrote and maintain an Elixir library, PromEx, that makes it a snap to export all sorts of metrics from your Elixir applications and get them on dashboards in Grafana. Let's explore some of the concepts surrounding Prometheus and see how we can leverage the Fly.io monitoring tools in an Elixir application to get slick looking dashboards like this one:
When customers are paying for your application or service, they expect it to work every time they reach for it. When things break or errors occur, your customers will not be happy. If you are lucky, your customers send you an email letting you know that things are not working as expected. Unfortunately, many of these occurrences go unreported.
