3 KiB
Manage feature flags
Starting from GitLab 9.3 we support feature flags for features in GitLab via
Flipper. You should use the Feature
class (defined in lib/feature.rb) in your code to get, set and list feature
flags.
During runtime you can set the values for the gates via the features API (accessible to admins only).
Feature groups
Starting from GitLab 9.4 we support feature groups via Flipper groups.
Feature groups must be defined statically in lib/feature.rb (in the
.register_feature_groups method), but their implementation can obviously be
dynamic (querying the DB etc.).
Once defined in lib/feature.rb, you will be able to activate a
feature for a given feature group via the feature_group param of the features API
For GitLab.com, team members have access to feature flags through chatops. Only
percentage gates are supported at this time. Setting a feature to be used 50% of
the time, you should execute /chatops run feature set my_feature_flag 50.
Feature flags for user applications
GitLab does not yet support the use of feature flags in deployed user applications. You can follow the progress on that in the issue on our issue tracker.
Developing with feature flags
In general, it's better to have a group- or user-based gate, and you should prefer
it over the use of percentage gates. This would make debugging easier, as you
filter for example logs and errors based on actors too. Futhermore, this allows
for enabling for the gitlab-org group first, while the rest of the users
aren't impacted.
# Good
Feature.enabled?(:feature_flag, project)
# Avoid, if possible
Feature.enabled?(:feature_flag)
To use feature gates based on actors, the model needs to respond to
flipper_id. For example, to enable for the Foo model:
class Foo < ActiveRecord::Base
include FeatureGate
end
Features that are developed and are intended to be merged behind a feature flag should not include a changelog entry. The entry should be added in the merge request removing the feature flags.
In the rare case that you need the feature flag to be on automatically, use
default_enabled: true when checking:
Feature.enabled?(:feature_flag, project, default_enabled: true)
For more information about rolling out changes using feature flags, refer to the Rolling out changes using feature flags guide.
Specs
In the test environment Feature.enabled? is stubbed to always respond to true,
so we make sure behavior under feature flag doesn't go untested in some non-specific
contexts.
Whenever a feature flag is present, make sure to test both states of the feature flag. You can stub a feature flag as follows:
stub_feature_flags(my_feature_flag: false)