ABMeter is a feature-flag and A/B-testing platform. You define parameters, experiments, and feature flags in the ABMeter Lab; this gem reads the value assigned to each user in your Ruby app and reports events back.

Breaking change in 0.3.0: ABMeter.reset! now discards queued data without any network I/O; use ABMeter.reset for the previous drain-on-exit behavior.

abmeter supports Ruby 3.2 and newer.

Add this line to your application's Gemfile:

gem 'abmeter'

And then execute:

$ bundle install

Sign up at abmeter.ai, then in the Lab open API Keys and create one. Expose it to your app (e.g. as ABMETER_API_KEY).

Configure the client once at startup:

ABMeter.configure do |config|
  config.api_key = ENV['ABMETER_API_KEY']
end

The example below assumes a parameter welcome_text (in a space, with a variant, controlled by a running experiment or feature flag) and an event type user_purchases_plan already exist — create them through the ABMeter API or, more easily, your AI assistant over MCP. Until they do, resolve_parameter just returns the parameter's default and track_event rejects unknown event types.

# In request handling: read the value assigned to this user. `user_id` is the
# only required field; an optional `email:` is available for predicate-based
# (email-pattern) audience targeting.
user = ABMeter::User.new(user_id: current_user.id)
text = ABMeter.resolve_parameter(user: user, parameter_slug: 'welcome_text')

# In business logic: record an action that feeds a metric.
ABMeter.track_event('user_purchases_plan', current_user.id, { plan: purchased_plan.name, price: purchased_plan.price })

The two calls are one loop: the experiment varies welcome_text, and the event feeds a metric whose effect the experiment measures across variants. Note that resolve_parameter is not a pure read — it resolves the value locally and records an exposure in the background; use get_exposure for the same resolution without submitting. Full guides live at abmeter.ai.

# Graceful — bounded blocking, flushes pending exposures/events.
# Returns true on clean shutdown, false if the timeout elapsed.
ABMeter.reset(timeout: 5.0)

# Immediate — non-blocking, discards anything still queued.
# Use only when the process is exiting *right now* and you cannot afford I/O.
ABMeter.reset!

The gem uses mise to pin Ruby (mise.toml). Pure-Ruby — no Postgres / Redis required.

brew install mise            # one-time
mise install                 # one-time: install pinned Ruby
bundle install
bundle exec rspec            # tests
bundle exec rubocop          # lint (if .rubocop.yml present)

The gem is tested against Ruby 3.2, 3.3, 3.4, and 4.0.

The gem is available as open source under the terms of the MIT License.