Arturo provides feature sliders for Rails. It lets you turn features on and off just like feature flippers, but offers more fine-grained control. It supports deploying features only for a given percentage of your users and whitelisting and blacklisting users based on any criteria you can express in Ruby.
The selection is deterministic. So if a user has a feature on Monday, the user will still have it on Tuesday (unless you decrease the feature's deployment percentage or change its white- or blacklist settings).
Trish, a developer is working on a new feature: a live feed of recent postings in the user's city that shows up in the user's sidebar. First, she uses Arturo's view helpers to control who sees the sidebar widget:
<%# in app/views/layout/_sidebar.html.erb: %>
<% if_feature_enabled(:live_postings) do %>
<div class='widget'>
<h3>Recent Postings</h3>
<ol id='live_postings'>
</ol>
</div>
<% end %>
Then Trish writes some Javascript that will poll the server for recent postings and put them in the sidebar widget:
// in public/javascript/live_postings.js:
$(function() {
var livePostingsList = $('#live_postings');
if (livePostingsList.length > 0) {
var updatePostingsList = function() {
livePostingsList.load('/listings/recent');
setTimeout(updatePostingsList, 30);
}
updatePostingsList();
}
});
Trish uses Arturo's Controller filters to control who has access to the feature:
# in app/controllers/postings_controller:
class PostingsController < ApplicationController
require_feature :live_postings, only: :recent
# ...
end
Trish then deploys this code to production. Nobody will see the feature yet,
since it's not on for anyone. (In fact, the feature doesn't yet exist
in the database, which is the same as being deployed to 0% of users.) A week
later, when the company is ready to start deploying the feature to a few
people, the product manager, Vijay, signs in to their site and navigates
to /features
, adds a new feature called "live_postings" and sets its
deployment percentage to 3%. After a few days, the operations team decides
that the increase in traffic is not going to overwhelm their servers, and
Vijay can bump the deployment percentage up to 50%. A few more days go by
and they clean up the last few bugs they found with the "live_postings"
feature and deploy it to all users.
gem 'arturo'
rails g arturo:migration
rails g arturo:initializer
rails g arturo:routes
rails g arturo:assets
rails g arturo:feature_model
rake db:migrate
By default, the generated model Arturo::Feature
inherits from ActiveRecord::Base
. However, if you’re using multiple databases your models should inherit from an abstract class that specifies a database connection, not directly from ActiveRecord::Base
. Update the generated model in app/models/arturo/feature.rb
to make it use a correct database.
Open up the newly-generated config/initializers/arturo_initializer.rb
.
There are configuration options for the following:
- logging capabilities (see logging)
- the method that determines whether a user has permission to manage features (see admin permissions)
- the method that returns the object that has features (e.g. User, Person, or Account; see feature recipients)
- whitelists and blacklists for features (see white- and blacklisting)
Open up the newly-generated public/stylesheets/arturo_customizations.css
.
You can add any overrides you like to the feature configuration page styles
here. Do not edit public/stylesheets/arturo.css
as that file may be
overwritten in future updates to Arturo.
Arturo is a Rails engine. I want to promote reuse on other frameworks by extracting key pieces into mixins, though this isn't done yet. Open an issue and I'll be happy to work with you on support for your favorite framework.
You can provide a logger in order to inspect Arturo usage. A potential implementation for Rails would be:
Arturo.logger = Rails.logger
Arturo::FeatureManagement#may_manage_features?
is a method that is run in
the context of a Controller or View instance. It should return true
if
and only if the current user may manage permissions. The default implementation
is as follows:
current_user.present? && current_user.admin?
You can change the implementation in
config/initializers/arturo_initializer.rb
. A reasonable implementation
might be
Arturo.permit_management do
signed_in? && current_user.can?(:manage_features)
end
Clients of Arturo may want to deploy new features on a per-user, per-project, per-account, or other basis. For example, it is likely Twitter deployed "#newtwitter" on a per-user basis. Conversely, Facebook -- at least in its early days -- may have deployed features on a per-university basis. It wouldn't make much sense to deploy a feature to one user of a Basecamp project but not to others, so 37Signals would probably want a per-project or per-account basis.
Arturo::FeatureAvailability#feature_recipient
is intended to support these
many use cases. It is a method that returns the current "thing" (a user, account,
project, university, ...) that is a member of the category that is the basis for
deploying new features. It should return an Object
that responds to #id
.
The default implementation simply returns current_user
. Like
Arturo::FeatureManagement#may_manage_features?
, this method can be configured
in config/initializers/arturo_initializer.rb
. If you want to deploy features
on a per-account basis, a reasonable implementation might be
Arturo.feature_recipient do
current_account
end
or
Arturo.feature_recipient do
current_user.account
end
If the block returns nil
, the feature will be disabled.
Whitelists and blacklists allow you to control exactly which users or accounts
will have a feature. For example, if all premium users should have the
:awesome
feature, place the following in
config/initializers/arturo_initializer.rb
:
Arturo::Feature.whitelist(:awesome) do |user|
user.account.premium?
end
If, on the other hand, no users on the free plan should have the
:awesome
feature, place the following in
config/initializers/arturo_initializer.rb
:
Arturo::Feature.blacklist(:awesome) do |user|
user.account.free?
end
If you want to whitelist or blacklist large groups of features at once, you can move the feature argument into the block:
Arturo::Feature.whitelist do |feature, user|
user.account.has?(feature.to_sym)
end
All that configuration is just a waste of time if Arturo didn't modify the behavior of your application based on feature availability. There are a few ways to do so.
If an action should only be available to those with a feature enabled,
use a before filter. The following will raise a 403 Forbidden error for
every action within BookHoldsController
that is invoked by a user who
does not have the :hold_book
feature.
class BookHoldsController < ApplicationController
require_feature :hold_book
end
require_feature
accepts as a second argument a Hash
that it passes on
to before_action
, so you can use :only
and :except
to specify exactly
which actions are filtered.
If you want to customize the page that is rendered on 403 Forbidden
responses, put the view in
RAILS_ROOT/app/views/arturo/features/forbidden.html.erb
. Rails will
check there before falling back on Arturo's forbidden page.
Both controllers and views have access to the if_feature_enabled?
and
feature_enabled?
methods. The former is used like so:
<% if_feature_enabled?(:reserve_table) %>
<%= link_to 'Reserve a table', new_restaurant_reservation_path(:restaurant_id => @restaurant) %>
<% end %>
The latter can be used like so:
def widgets_for_sidebar
widgets = []
widgets << twitter_widget if feature_enabled?(:twitter_integration)
...
widgets
end
require 'arturo'
use Arturo::Middleware, feature: :my_feature
If you want to check availability outside of a controller or view (really
outside of something that has Arturo::FeatureAvailability
mixed in), you
can ask either
Arturo.feature_enabled_for?(:foo, recipient)
or the slightly fancier
Arturo.foo_enabled_for?(recipient)
Both check whether the foo
feature exists and is enabled for recipient
.
Note: Arturo has support for caching Feature
lookups, but doesn't yet
integrate with Rails's caching. This means you should be very careful when
caching actions or pages that involve feature detection as you will get
strange behavior when a user who has access to a feature requests a page
just after one who does not (and vice versa).
To enable caching Feature
lookups, mix Arturo::FeatureCaching
into
Arturo::Feature
and set the cache_ttl
. This is best done in an
initializer:
Arturo::Feature.extend(Arturo::FeatureCaching)
Arturo::Feature.cache_ttl = 10.minutes
You can also warm the cache on startup:
Arturo::Feature.warm_cache!
This will pre-fetch all Feature
s and put them in the cache.
To use the current cache state when you can't fetch updates from origin:
Arturo::Feature.extend_cache_on_failure = true
The following is the intended support for integration with view caching:
Both the require_feature
before filter and the if_feature_enabled
block
evaluation automatically append a string based on the feature's
last_modified
timestamp to cache keys that Rails generates. Thus, you don't
have to worry about expiring caches when you increase a feature's deployment
percentage. See Arturo::CacheSupport
for more information.
Arturo gets its name from Professor Maximillian Arturo on Sliders.