RailsConf 2025: OpenTelemetry Workshop

This repository is still a work in progress. You may need to pull before the workshop to get the latest copy.

This repository accompanies a workshop titled "How to instrument your Rails app with OpenTelemetry" that will be held at RailsConf 2025 in Philadelphia on July 9, 2025.

Overview

This repository has two applications in it:

• hike-tracker_original: This is an uninstrumented copy of the application we'll be working with. It uses Rails 8.0 and Ruby 3.4.2.

• hike-tracker-instrumented: This is how the application will look at the end of the workshop, after being instrumented with OpenTelemetry.

For the workshop, please cd into hike-tracker_original and work from that application.

If you want to check your work, or copy/paste the code, consult hike-tracker-instrumented.

Hot tip: Bundling the hike-tracker_original application before the workshop will help reduce the burden on the Wifi in the conference room during the event!

Prerequsities

Before the workshop, I recommend that you have:

• Ruby 3.4.2 installed (you can use any version 3.1 or above, but will need to update the .ruby-version file)
• SQLite installed - brew install sqlite
• An observability backend to visualize your data

Initial setup

cd hike-tracker_original
bin/setup

This will:

• Bundle the application
• Prepare the database (this includes seeding if it creates the database)
• Start the Rails server

Development

To run the application:

cd hike-tracker_original
bin/rails db:seed # optional if you've already seeded
bin/rails server

In a separate terminal window, you can generate traffic for your application using:

cd hike-tracker_original
script/traffic.sh

This traffic script will make requests to the index and show pages for the Users, Trails, and Activities controllers. It may make requests to show pages with IDs that don't exist. This will help us see how OpenTelemetry handles errors.

To stop the script, enter: CTRL + C

You can also generate traffic by clicking around in the UI.

The Data model

During the workshop, we'll be using a simple Rails application designed to track hikes. There are three main resources: Users, Trails, and Activities.

An Activity belongs to a User and a Trail. Trails can also have many comments.

We'll put the majority of our custom instrumentation in the Activity-related code.

Observability backend recommendations

One of the beautiful things about OpenTelemetry is its vendor-agnostic nature. It doesn't deal with how to visualize your data, only how to collect and shape your data.

Evaluating your options for ingesting and storing your OpenTelemetry data is outside the scope of this workshop. OpenTelemetry's vendors page has an extensive list of available options.

The examples in this workshop use New Relic as the backend vendor. New Relic has has a free forever tier that you can sign up for here.

If you choose to use New Relic, you need a License Key for your account.

You can also follow the instructions for this workshop using a different vendor, or choose to export everything to the console and examine your data there.