Acme Donuts

Example project in Ruby on Rails implementing the GrowthBook Ruby SDK.

The project uses SQLite for simplicity.

• Dependencies
• Development Server
• Usage
• Features
• Navigating the code
  • Caching

Dependencies

The required Ruby version is in .ruby-version.

Install the dependencies:

bundle install

Development Server

Run the migrations and seed the database with the sample users:

bundle exec rails db:migrate
bundle exec rails db:seed

This will create sample users in the database.

Run the development server:

bundle exec rails server -p 3333

This will run the dev server at: http://127.0.0.1:3333

You can access the REPL and models:

bundle exec rails console

Usage

You can make requests to any of the endpoints as any of the below users.

Include the access_token as the Authorization: Bearer {token} header.

id	email	access_token
1	[email protected]	user_tina_abc123
2	[email protected]	employee_acme_xyz987

Here's an example request as an employee of Acme:

curl --header "Authorization: Bearer employee_acme_xyz987" http://localhost:3333/user

You should see the following response:

{
  "growthbook_user_attributes": {
    "id": "user-employee-123456789",
    "country": "spain",
    "email": "[email protected]",
    "employee": true,
    "loggedIn": true
  }
}

Here's an example request as a non-employee of Acme:

curl --header "Authorization: Bearer user_tina_abc123" http://localhost:3333/user

You should see the following response:

{
  "growthbook_user_attributes": {
    "id": "user-abc123",
    "country": "france",
    "email": "[email protected]",
    "employee": false,
    "loggedIn": true
  }
}

You should get an error if you make any request without a token, e.g.:

curl -sI http://localhost:3333/user | grep HTTP

You should see the following response:

HTTP/1.1 401 Unauthorized

Features

Make a request to the features endpoint to evaluate features for a given user.

Here's an example request as an employee of Acme:

curl --header "Authorization: Bearer employee_acme_xyz987" http://localhost:3333/features

You should see the following response:

{
  "banner_text": "¡Bienvenidos y bienvenidas a Donas Acme!",
  "use_dark_mode": true,
  "donut_price": 0,
  "username_color": "orange"
}

Here's an example request as a non-employee of Acme:

curl --header "Authorization: Bearer user_tina_abc123" http://localhost:3333/features

You should see the following response:

{
  "banner_text": "Bienvenue au Beignets Acme !",
  "use_dark_mode": true,
  "donut_price": 2.5,
  "username_color": "yellow"
}

Navigating the code

The ApplicationController implements authentication as well as initializing the GrowthBook SDK for the authenticated user.

See the growthbook_sdk controller concern for implementation details. This implements cacheing of the GrowthBook features JSON. More on that below.

The UserController has one method that returns the user attributes that are assigned to the GrowthBook SDK.

The FeatureController is where the GrowthBook SDK is implemented:

• #eval_feature(feature_key)
• #on?(feature_key)
• #feature_value(feature_key, default_value)
• #run(experiment) with an inline experiment Growthbook::InlineExperiment

See the class GrowthbookImpressionListener for an example impression listener, which is evaluated whenever an inline experiment is run. Whenever the GET /features endpoint is evaluated, an inline experiment is run and the experiment results are stored using the Impression model. You can see them in the console by calling Impression.all. This is done for the username_color property.

The view layer uses blueprinter to serialize models into JSON but you can use active_model_serializers, jbuilder, or any other way of creating JSON for the GrowthBook attributes.

Impression.all output

[#<Impression:0x00007f79d8d184f0
  id: 1,
  experiment:
   {"key"=>"username-color",
    "variations"=>["red", "orange", "yellow", "green", "blue", "purple"],
    "active"=>true,
    "force"=>nil,
    "weights"=>nil,
    "coverage"=>1,
    "condition"=>nil,
    "namespace"=>nil,
    "hash_attribute"=>"id"},
  result:
   {"hash_used"=>true,
    "in_experiment"=>true,
    "variation_id"=>2,
    "value"=>"yellow",
    "hash_attribute"=>"id",
    "hash_value"=>"user-abc123",
    "feature_id"=>""},
  created_at: Wed, 07 Dec 2022 01:04:08.843090000 UTC +00:00,
  updated_at: Wed, 07 Dec 2022 01:04:08.843090000 UTC +00:00>,
 #<Impression:0x00007f79dbadb590
  id: 2,
  experiment:
   {"key"=>"username-color",
    "variations"=>["red", "orange", "yellow", "green", "blue", "purple"],
    "active"=>true,
    "force"=>nil,
    "weights"=>nil,
    "coverage"=>1,
    "condition"=>nil,
    "namespace"=>nil,
    "hash_attribute"=>"id"},
  result:
   {"hash_used"=>true,
    "in_experiment"=>true,
    "variation_id"=>1,
    "value"=>"orange",
    "hash_attribute"=>"id",
    "hash_value"=>"user-employee-123456789",
    "feature_id"=>""},
  created_at: Wed, 07 Dec 2022 01:04:17.700329000 UTC +00:00,
  updated_at: Wed, 07 Dec 2022 01:04:17.700329000 UTC +00:00>]

Caching

This example implements in-memory caching with MemoryStore, which is not persisted across server restarts. For a caching implementation more suitable for production, you can use another cache strategy, for example RedisCacheStore.

To see that caching is working, run the following:

bundle exec rails dev:cache

You should see the confirmation message that development mode is now being cached.

You can see the caching implementation in the growthbook_sdk controller concern.