Add percentage of actors feature flag rollout

Currently only percentage of times rollout is possible on the feature
flag API. With that change we shall be able to use the chatops to set
percentage of actors rollout for any feature flag

changelogs/unreleased/214678-add-an-api-for-flipper-percentage-of-actors-rollout.yml

+---
+title: Add percentage of actors feature flag rollout
+merge_request: 29698
+author:
+type: added

lib/api/features.rb

@@ -16,6 +16,15 @@ module API
         end
       end
 
+      def gate_key(params)
+        case params[:key]
+        when 'percentage_of_actors'
+          :percentage_of_actors
+        else
+          :percentage_of_time
+        end
+      end
+
       def gate_targets(params)
         Feature::Target.new(params).targets
       end
@@ -40,15 +49,22 @@ module API
       end
       params do
         requires :value, type: String, desc: '`true` or `false` to enable/disable, an integer for percentage of time'
+        optional :key, type: String, desc: '`percentage_of_actors` or the default `percentage_of_time`'
         optional :feature_group, type: String, desc: 'A Feature group name'
         optional :user, type: String, desc: 'A GitLab username'
         optional :group, type: String, desc: "A GitLab group's path, such as 'gitlab-org'"
         optional :project, type: String, desc: 'A projects path, like gitlab-org/gitlab-ce'
+
+        mutually_exclusive :key, :feature_group
+        mutually_exclusive :key, :user
+        mutually_exclusive :key, :group
+        mutually_exclusive :key, :project
       end
       post ':name' do
         feature = Feature.get(params[:name])
         targets = gate_targets(params)
         value = gate_value(params)
+        key = gate_key(params)
 
         case value
         when true
@@ -64,7 +80,11 @@ module API
             feature.disable
           end
         else
-          feature.enable_percentage_of_time(value)
+          if key == :percentage_of_actors
+            feature.enable_percentage_of_actors(value)
+          else
+            feature.enable_percentage_of_time(value)
+          end
         end
 
         present feature, with: Entities::Feature, current_user: current_user

spec/requests/api/features_spec.rb

@@ -198,7 +198,7 @@ describe API::Features do
         end
       end
 
-      it 'creates a feature with the given percentage if passed an integer' do
+      it 'creates a feature with the given percentage of time if passed an integer' do
         post api("/features/#{feature_name}", admin), params: { value: '50' }
 
         expect(response).to have_gitlab_http_status(:created)
@@ -210,6 +210,19 @@ describe API::Features do
             { 'key' => 'percentage_of_time', 'value' => 50 }
           ])
       end
+
+      it 'creates a feature with the given percentage of actors if passed an integer' do
+        post api("/features/#{feature_name}", admin), params: { value: '50', key: 'percentage_of_actors' }
+
+        expect(response).to have_gitlab_http_status(:created)
+        expect(json_response).to eq(
+          'name' => 'my_feature',
+          'state' => 'conditional',
+          'gates' => [
+            { 'key' => 'boolean', 'value' => false },
+            { 'key' => 'percentage_of_actors', 'value' => 50 }
+          ])
+      end
     end
 
     context 'when the feature exists' do
@@ -298,7 +311,7 @@ describe API::Features do
         end
       end
 
-      context 'with a pre-existing percentage value' do
+      context 'with a pre-existing percentage of time value' do
         before do
           feature.enable_percentage_of_time(50)
         end
@@ -316,6 +329,25 @@ describe API::Features do
             ])
         end
       end
+
+      context 'with a pre-existing percentage of actors value' do
+        before do
+          feature.enable_percentage_of_actors(42)
+        end
+
+        it 'updates the percentage of actors if passed an integer' do
+          post api("/features/#{feature_name}", admin), params: { value: '74', key: 'percentage_of_actors' }
+
+          expect(response).to have_gitlab_http_status(:created)
+          expect(json_response).to eq(
+            'name' => 'my_feature',
+            'state' => 'conditional',
+            'gates' => [
+              { 'key' => 'boolean', 'value' => false },
+              { 'key' => 'percentage_of_actors', 'value' => 74 }
+            ])
+        end
+      end
     end
   end