We sometimes employ feature flags to develop features that aren't fully formed at the moment of deployment. They can also be employed to roll out features in production incrementally.
Feature flags are meant to be temporary and part of a rollout plan resulting in their removal.
To create a new feature flag, we use data update scripts so that they can be made available over the entire Forem fleet, for example:
bundle exec rails g data_update AddAwesomeAlgorithmFeatureFlag
This will generate a script and its spec. Once done, you can add the new feature flag like this:
module DataUpdateScripts class AddAwesomeAlgorithmFeatureFlag def run FeatureFlag.add(:awesome_algorithm) end endend
and then start using it right away.
Once the feature flag is added, you can start using it to hide the feature behind a boolean flag:
if FeatureFlag.enabled?(:awesome_algorithm) # call the new codeelse # call the previous codeend
or, for example in a view:
<% if FeatureFlag.enabled?(:blue_button) %> <%= render "blue_button" %><% else %> <%= render "good_old_button" %><% end %>
As mentioned, feature flags can be used to test a work in progress feature or to test a new approach directly in production.
To enable such a feature:
- Log in to the Forem
- Go to
/admin/feature_flags(it requires the
- Click on the flag you want to enable and press "Fully Enable".
Once the feature has been validated and finalized or discarded, please remember to remove its flag with a final data update script, for example:
bundle exec rails g data_update RemoveAwesomeAlgorithmFeatureFlag
module DataUpdateScripts class AwesomeAlgorithmFeatureFlag def run FeatureFlag.remove(:awesome_algorithm) end endend
This will ensure that the feature will be removed from all Forems.