Tutorial: Use GitLab Observability with a Ruby on Rails application

DETAILS: Tier: Ultimate Offering: GitLab.com Status: Beta

FLAG: The availability of this feature is controlled by a feature flag. For more information, see the history of the Distributed tracing feature.

In this tutorial, you'll learn how to create, configure, instrument, and monitor a Ruby on Rails application using GitLab Observability features.

Before you begin

Take a moment and make sure you have the following:

A GitLab Ultimate subscription for GitLab.com
A local installation of Ruby on Rails
Basic knowledge of Git, Ruby on Rails, and the core concepts of OpenTelemetry

Create a new GitLab project

First, create a new GitLab project and a corresponding access token. This tutorial uses the project name animals.

On the left sidebar, at the top, select Create new ({plus}) and New project/repository.
Select Create blank project.
Enter the project details.
- In the Project name field, enter animals.
Select Create project.
In the animals project, on the left sidebar, select Settings > Access tokens.
Create a new access token with the Owner role and the read_api and write_observability scopes. Store the token value somewhere safe—you'll need it later.

Create a Rails application

Next, we need a new Ruby on Rails application that we can instrument. For this tutorial, let's create a toy application to store a list of animals.

To create an application:

From the command line, run the following:
```
rails new animals
```
Go to the animals directory and run the application:
```
cd animals
rails server -p 8080
```
In a web browser, visit http://localhost:8080 and make sure the application is running correctly.

Create a model scaffold for an Animal class and run the generated database migrations:

rails generate scaffold Animal species:string number_of_legs:integer dangerous:boolean
rails db:migrate

Run the application again and visit the list of animals at http://localhost:8080/animals. Try creating, editing, and deleting an animal to make sure everything works as expected.

Add the OpenTelemetry and dotenv gems to the Gemfile:

bundle add opentelemetry-sdk opentelemetry-instrumentation-all opentelemetry-exporter-otlp dotenv

Create an initializer to handle the configuration, and add an .env file to store environment variables:
```
touch config/initializers/opentelemetry.rb
touch .env
```

Edit config/initializers/opentelemetry.rb and add the following code:

require 'opentelemetry/sdk'
require 'opentelemetry/instrumentation/all'
require 'opentelemetry-exporter-otlp'

OpenTelemetry::SDK.configure do |c|
  c.service_name = 'animals-rails'
  c.use_all()
end

Find your group ID:
1. On the left sidebar, select Search or go to and find the top-level group with the animal project. For example, if your project URL is https://gitlab.com/tankui/observability/animal, the top-level group is tanuki.
2. On the group overview page, in the upper-right corner, select Actions ({ellipsis_v}).
3. Select Copy group ID. Save the copied ID for later.
Find your project ID:
1. On the animal project overview page, in the upper-right corner, select Actions ({ellipsis_v}).
2. Select Copy project ID. Save the copied ID for later.

Edit .env and add the following code:

OTEL_EXPORTER = "otlphttp"
OTEL_EXPORTER_OTLP_ENDPOINT = "https://observe.gitlab.com/v3/{{GROUP_ID}}/{{PROJECT_ID}}/ingest"
OTEL_EXPORTER_OTLP_HEADERS = "PRIVATE-TOKEN={{ACCESS_TOKEN}}"
OTEL_LOG_LEVEL = "debug"

Be sure to replace the GROUP_ID, PROJECT_ID, and ACCESS_TOKEN with the values you obtained earlier.

View traces

Now that you have an application configured to use Observability tracing, you can view exported traces on GitLab.com.

To view exported traces:

Start the animals application again.
Visit http://localhost:8080/animals and perform some actions in the application.
In the animals project, on the left sidebar, select Monitor > Traces. If everything is working correctly, you should see a trace for each controller action.
Optional. Select a trace to view its span.

Congratulations! You successfully created an application, configured it to use GitLab Observability features, and examined the traces the application created. You can continue to experiment with this toy application, or try configuring a more complex application to export traces.

Remember that Observability Tracing is not yet ready for production use. There is no official support for logs or metrics using the OpenTelemetry collector with a Ruby on Rails application.