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Reforge.init

context = {
  user: {
    key: 123,
    email: "alice@example.com"
  }
  team: {
    key: 456,
    name: "AliceCorp"
  }
}

result = Reforge.enabled? "my-first-feature-flag", context

puts "my-first-feature-flag is: #{result}"

Initialize Client

If you set REFORGE_BACKEND_SDK_KEY as an environment variable, initializing the client is as easy as

Reforge.init # reads REFORGE_BACKEND_SDK_KEY env var by default

Rails Applications

Initializing Reforge in your application.rb will allow you to reference dynamic configuration in your environment (e.g. staging.rb) and initializers. This is useful for setting environment-specific config like your redis connection URL.

#application.rb
module MyApplication
  class Application < Rails::Application
    #...

    Reforge.init
  end
end

Special Considerations with Forking servers like Puma & Unicorn that use workers

Many ruby web servers fork. In order to work properly we should have a Reforge Client running independently in each fork. You do not need to do this if you are only using threads and not workers. If using SemanticLogger, you will also need to reopen the logger in each fork.

Puma

If using workers in Puma, you can initialize inside an on_worker_boot hook in your puma.rb config file.

# puma.rb
on_worker_boot do
  Reforge.fork
  SemanticLogger.reopen # if you are using SemanticLogger
end

Unicorn

If using workers in Unicorn, you can initialize inside an after_fork hook in your unicorn.rb config file:

# unicorn.rb
after_fork do |server, worker|
  Reforge.fork
  SemanticLogger.reopen # if you are using SemanticLogger
end

Feature Flags

For boolean flags, you can use the enabled? convenience method:

if Reforge.enabled?("my-first-feature-flag")
  # ...
else
  # ...
end

Feature flags don't have to return just true or false.

You can get other data types using get:

Reforge.get("ff-with-string")
Reforge.get("ff-with-int")

Context

Feature flags become more powerful when we give the flag evaluation rules more information to work with. We do this by providing context of the current user (and/or team, request, etc.)

Global Context

When initializing the client, you can set a global context that will be used for all evaluations.

Reforge.init(
  global_context: {
    application: {key: "my.corp.web"},
    cpu: {count: 4},
    clock: {timezone: "UTC"}
  }
)

Global context is the least specific context and will be overridden by more specific context passed in at the time of evaluation.

Thread-local (Request-scoped)

To make the best use of Reforge, we recommend setting context in an around_action in your ApplicationController. Setting this context for the life-cycle of the request means the Reforge logger can be aware of your user/etc and you won't have to explicitly pass context into your .enabled? and .get calls.

# application_controller.rb
class ApplicationController < ActionController::Base
  around_action do |_, block|
    Reforge.with_context(reforge_context, &block)
  end

  def reforge_context
    {
      device: {
        mobile: mobile?
        # ...
      },
    }.merge(reforge_user_context)
  end

  def reforge_user_context
    return {} unless current_user

    {
      key: current_user.tracking_id,
      id: current_user.id,
      email: current_user.email,
      country: current_user.country,
      # ...
    }
  end
end

Just-in-time Context

You can also pass context when evaluating individual flags or config values.

context = {
  user: {
    id: 123,
    key: 'user-123',
    subscription_level: 'pro',
    email: "alice@example.com"
  },
  team: {
    id: 432,
    key: 'team-abc',
  },
  device: {
    key: "abcdef",
    mobile: true,
  }
}
result = Reforge.enabled?("my-first-feature-flag", context)

puts "my-first-feature-flag is: #{result} for #{context.inspect}"

Dynamic Config

Config values are accessed the same way as feature flag values. You can use enabled? as a convenience for boolean values, and get works for all data types

config_key = "my-first-int-config"
puts "#{config_key} is: #{Reforge.get(config_key)}"

Default Values for Configs

Here we ask for the value of a config named max-jobs-per-second, and we specify 10 as a default value if no value is available.

Reforge.get("max-jobs-per-second", 10) # => returns `10` if no value is available

If we don't provide a default and no value is available, a Reforge::Errors::MissingDefaultError error will be raised.

Reforge.get("max-jobs-per-second") # => raises if no value is available

note

You can modify this behavior by setting the option on_no_default to Reforge::Options::ON_NO_DEFAULT::RETURN_NIL

Telemetry

By default, Reforge uploads telemetry that enables a number of useful features. You can alter or disable this behavior using the following options:

Name	Description	Default
collect_evaluation_summaries	Send counts of config/flag evaluation results back to Reforge to view in web app	true
collect_logger_counts	Send counts of logger usage back to Reforge to power log-levels configuration screen	true
context_upload_mode	Upload either context "shapes" (the names and data types your app uses in Reforge contexts) or periodically send full example contexts	:periodic_example

If you want to change any of these options, you can pass an options object when initializing the Reforge client.

#application.rb
module MyApplication
  class Application < Rails::Application
    #...

    options = Reforge::Options.new(
      collect_evaluation_summaries: true,
      collect_logger_counts: true,
      context_upload_mode: :periodic_example,
    )

    Reforge.init(options)
  end
end

Debugging

In the rare case that you are trying to debug issues that occur within the library, set env var

REFORGE_LOG_CLIENT_BOOTSTRAP_LOG_LEVEL = debug

Asset Precompilation in Rails

Developers trying to run rake assets:precompile or rails assets:precompile in CI/CD know the pain of missing environment variables. Reforge can help with this, but you don't want to hardcode your Reforge SDK key in your Dockerfile. What should you do instead?

We recommend using a datafile for assets:precompile. You can generate a datafile for your environment using the Reforge CLI:

reforge download --environment test

This will generate a JSON file (e.g., reforge.test.108.config.json) based on your Reforge project’s test environment. You can check into your repo for use in CI/CD and automated testing.

Now you can use the datafile for assets:precompile:

REFORGE_DATAFILE=reforge.test.108.config.json bundle exec rake assets:precompile

Of course, you can generate a datafile for any environment you like and use it in the same way.

Bootstrap & Stub Client-side JavaScript flags and configs

If you're using JavaScript on the client side, you can use the Reforge Ruby client to bootstrap your client-side flags and configs. This helps you avoid loading states while you wait on an HTTP request to Reforge's evaluation endpoint. You can skip the HTTP request altogether.

With the Frontend SDKs

If you want the power of the JavaScript SDK or React SDK, you can use the Ruby client to bootstrap the page with the evaluated flags and configs for the current user context. Just put this in the DOM (perhaps in your application layout) before you load your Reforge frontend SDK.

<%== Reforge.bootstrap_javascript(context) %>

Things work as they normally would with the frontend SDKs, you'll just skip the HTTP request.

Without the Frontend SDKs

If you don't want to use the frontend SDKs, you can get a global window.reforge object to call get and isEnabled on the client side.

<%= Reforge.generate_javascript_stub(context, callback = nil) %>

This will give you feature flags and config values for your current context. You can provide an optional callback to record experiment exposures or other metrics. No HTTP request or SDK needed!

Testing

Test Setup

You can use a datafile for consistency, reproducibility, and offline testing. See Testing with DataFiles.

If you need to test multiple scenarios that depend on a single config or feature key, you can change the Reforge value using a mock or stub.

Example Test

Imagine we want to test a batches method on our Job class. batches depends on job.batch.size and the value for job.batch.size in our default config file is 3.

We can test how batches performs with different values for job.batch.size by mocking the return value of Reforge.get.

class Job < Array
  def batches
    slice_size = Reforge.get('job.batch.size')
    each_slice(slice_size)
  end
end

RSpec.describe Job do
  describe '#batches' do
    it 'returns batches of jobs' do
      jobs = Job.new([1, 2, 3, 4, 5])

      expect(jobs.batches.map(&:size)).to eq([3, 2])

      allow(Reforge).to receive(:get).with('job.batch.size').and_return(2)
      expect(jobs.batches.map(&:size)).to eq([2, 2, 1])
    end
  end
end

Reference

Client Initialization Options

For more control, you can initialize your client with options. Here are the defaults with explanations.

options = Reforge::Options.new(
  sdk_key: ENV['REFORGE_BACKEND_SDK_KEY'],
  on_no_default: ON_NO_DEFAULT::RAISE, # options :raise, :warn_and_return_nil,
  initialization_timeout_sec: 10, # how long to wait before on_init_failure
  on_init_failure: ON_INITIALIZATION_FAILURE::RAISE, # choose to crash or continue with local data only if unable to fetch config data from prefab at startup
  datafile: ENV['REFORGE_DATAFILE'] || ENV['PREFAB_DATAFILE'],
  collect_logger_counts: true, # send counts of logger usage back to Reforge to power log-levels configuration screen
  collect_max_paths: DEFAULT_MAX_PATHS,
  collect_sync_interval: nil,
  context_upload_mode: :periodic_example, # :periodic_example, :shape_only, :none
  context_max_size: DEFAULT_MAX_EVAL_SUMMARIES,
  collect_evaluation_summaries: true, # send counts of config/flag evaluation results back to Reforge to view in web app
  collect_max_evaluation_summaries: DEFAULT_MAX_EVAL_SUMMARIES,
  allow_telemetry_in_local_mode: false,
  global_context: {}
)

Reforge.init(options)