Ruby gem for querying feature flags
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EightBall is a feature toggle querying gem


Add this line to your application's Gemfile:

gem 'eight_ball'

And then execute:

$ bundle

Or install it yourself as:

$ gem install eight_ball

Example Usage

require 'eight_ball'

# This could be read from the filesystem or be the response from an external service, etc.
json_input = %(
    "name": "Feature1",
    "enabledFor": [{
      "type": "range",
      "parameter": "accountId",
      "min": 1,
      "max": 10
    "disabledFor": [{
      "type": "list",
      "parameter": "accountId",
      "values": [2, 3]

# Transform the JSON into a list of Features
parser =
features = parser.parse json_input

# Tell EightBall about these Features
EightBall.provider = features

# Away you go
EightBall.enabled? "Feature1", { accountId: 4 } # true
EightBall.enabled? "Feature1", { accountId: 2 } # false

More examples here



A Feature is a part of your application that can be enabled or disabled based on various conditions. It has the following attributes:

  • name: The unique name of the Feature.
  • enabledFor: An array of Conditions for which the Feature is enabled.
  • disabledFor: An array of Conditions for which the Feature is disabled.


A Condition must either be true or false. It describes when a Feature is enabled or disabled.

Supported Conditions

  • Always: This condition is always satisfied.
  • List: This condition is satisfied if the given value belongs to its list of accepted values.
  • Never: This condition is never satisfied.
  • Range: This condition is satisfied if the given value is within the specified range (inclusive).


A Provider is able to give EightBall the list of Features it needs to answer queries.

Supported Providers

  • HTTP: Connect to a URL and use the given Parser to convert the response into a list of Features.
  • Static: Once initialized with a list of Features, always provides that same list of Features.


Some Providers are able to automatically "refresh" their list of Features using a RefreshPolicy.

Supported RefreshPolicies

  • Interval: The data is considered fresh for a given number of seconds, after which it is considered stale and should be refreshed.


A Parser converts the given input to an array of Features.

Supported Parsers


After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install.


Documentation is written using yard syntax. You can view the generated docs by running yard server and going to


Bug reports and pull requests are welcome on GitHub at