New created groups inherits integrations

When creating a new group, it should inherit the integrations following
the precedence of the closest integration from the ancestors of the
group or the instance-level integration.

app/models/service.rb

@@ -215,7 +215,7 @@ class Service < ApplicationRecord
     services_names.map { |service_name| "#{service_name}_service".camelize }
   end
 
-  def self.build_from_integration(project_id, integration)
+  def self.build_from_integration(id, integration, belongs_to_project = true)
     service = integration.dup
 
     if integration.supports_data_fields?
@@ -223,11 +223,17 @@ class Service < ApplicationRecord
       data_fields.service = service
     end
 
+    if belongs_to_project
+      service.group = nil
+      service.project_id = id
+    else
+      service.project = nil
+      service.group_id = id
+    end
+
     service.template = false
     service.instance = false
-    service.group = nil
     service.inherit_from_id = integration.id if integration.instance? || integration.group
-    service.project_id = project_id
     service.active = false if service.invalid?
     service
   end

app/services/groups/create_service.rb

@@ -28,9 +28,12 @@ module Groups
         @group.build_chat_team(name: response['name'], team_id: response['id'])
       end
 
+      Group.transaction do
         if @group.save
           @group.add_owner(current_user)
-        add_settings_record
+          @group.create_namespace_settings
+          create_services_from_active_default_integrations(@group) if Feature.enabled?(:group_level_integrations)
+        end
       end
 
       @group
@@ -84,8 +87,23 @@ module Groups
       params[:visibility_level] = Gitlab::CurrentSettings.current_application_settings.default_group_visibility
     end
 
-    def add_settings_record
-      @group.create_namespace_settings
+    # rubocop: disable CodeReuse/ActiveRecord
+    def create_services_from_active_default_integrations(group)
+      group_ids = group.ancestors.select(:id)
+
+      Service.from_union([
+        Service.active.where(instance: true),
+        Service.active.where(group_id: group_ids)
+      ]).order(by_type_group_ids_and_instance(group_ids)).group_by(&:type).each do |type, records|
+        Service.build_from_integration(group.id, records.first, false).save!
+      end
+    end
+    # rubocop: enable CodeReuse/ActiveRecord
+
+    def by_type_group_ids_and_instance(group_ids)
+      array = group_ids.to_sql.present? ? "array(#{group_ids.to_sql})" : 'ARRAY[]'
+
+      Arel.sql("type ASC, array_position(#{array}::bigint[], services.group_id), instance DESC")
     end
   end
 end

spec/models/service_spec.rb

@@ -360,7 +360,7 @@ RSpec.describe Service do
         end
 
         shared_examples 'service creation from an integration' do
-          it 'creates a correct service' do
+          it 'creates a correct service for a project integration' do
             service = described_class.build_from_integration(project.id, integration)
 
             expect(service).to be_active
@@ -373,6 +373,20 @@ RSpec.describe Service do
             expect(service.project).to eq(project)
             expect(service.group).to eq(nil)
           end
+
+          it 'creates a correct service for a group integration' do
+            service = described_class.build_from_integration(group.id, integration, false)
+
+            expect(service).to be_active
+            expect(service.url).to eq(url)
+            expect(service.api_url).to eq(api_url)
+            expect(service.username).to eq(username)
+            expect(service.password).to eq(password)
+            expect(service.template).to eq(false)
+            expect(service.instance).to eq(false)
+            expect(service.project).to eq(nil)
+            expect(service.group).to eq(group)
+          end
         end
 
         # this  will be removed as part of https://gitlab.com/gitlab-org/gitlab/issues/29404

spec/services/groups/create_service_spec.rb

@@ -138,4 +138,51 @@ RSpec.describe Groups::CreateService, '#execute' do
       expect(group.namespace_settings).to be_persisted
     end
   end
+
+  describe 'create service for the group' do
+    let(:service) { described_class.new(user, group_params) }
+    let(:created_group) { service.execute }
+
+    context 'with an active instance-level integration' do
+      let!(:instance_integration) { create(:prometheus_service, :instance, api_url: 'https://prometheus.instance.com/') }
+
+      it 'creates a service from the instance-level integration' do
+        expect(created_group.services.count).to eq(1)
+        expect(created_group.services.first.api_url).to eq(instance_integration.api_url)
+        expect(created_group.services.first.inherit_from_id).to eq(instance_integration.id)
+      end
+
+      context 'with an active group-level integration' do
+        let(:service) { described_class.new(user, group_params.merge(parent_id: group.id)) }
+        let!(:group_integration) { create(:prometheus_service, group: group, project: nil, api_url: 'https://prometheus.group.com/') }
+        let(:group) do
+          create(:group).tap do |group|
+            group.add_owner(user)
+          end
+        end
+
+        it 'creates a service from the group-level integration' do
+          expect(created_group.services.count).to eq(1)
+          expect(created_group.services.first.api_url).to eq(group_integration.api_url)
+          expect(created_group.services.first.inherit_from_id).to eq(group_integration.id)
+        end
+
+        context 'with an active subgroup' do
+          let(:service) { described_class.new(user, group_params.merge(parent_id: subgroup.id)) }
+          let!(:subgroup_integration) { create(:prometheus_service, group: subgroup, project: nil, api_url: 'https://prometheus.subgroup.com/') }
+          let(:subgroup) do
+            create(:group, parent: group).tap do |subgroup|
+              subgroup.add_owner(user)
+            end
+          end
+
+          it 'creates a service from the subgroup-level integration' do
+            expect(created_group.services.count).to eq(1)
+            expect(created_group.services.first.api_url).to eq(subgroup_integration.api_url)
+            expect(created_group.services.first.inherit_from_id).to eq(subgroup_integration.id)
+          end
+        end
+      end
+    end
+  end
 end