Move pipeline creation on MR create to Sidekiq

Doing this in the HTTP request means that if pipeline creation is slow,
the whole request can time out - and stop the pipeline being created.

For now, this is behind a feature flag so we can see if there are any
adverse effects.

app/services/merge_requests/after_create_service.rb

@@ -6,6 +6,12 @@ module MergeRequests
       event_service.open_mr(merge_request, current_user)
       notification_service.new_merge_request(merge_request, current_user)
 
+      # https://gitlab.com/gitlab-org/gitlab/issues/208813
+      if ::Feature.enabled?(:create_merge_request_pipelines_in_sidekiq, project)
+        create_pipeline_for(merge_request, current_user)
+        merge_request.update_head_pipeline
+      end
+
       merge_request.diffs(include_stats: false).write_cache
       merge_request.create_cross_references!(current_user)
     end

app/services/merge_requests/create_service.rb

@@ -20,8 +20,13 @@ module MergeRequests
 
       todo_service.new_merge_request(issuable, current_user)
       issuable.cache_merge_request_closes_issues!(current_user)
-      create_pipeline_for(issuable, current_user)
-      issuable.update_head_pipeline
+
+      # https://gitlab.com/gitlab-org/gitlab/issues/208813
+      unless ::Feature.enabled?(:create_merge_request_pipelines_in_sidekiq, project)
+        create_pipeline_for(issuable, current_user)
+        issuable.update_head_pipeline
+      end
+
       Gitlab::UsageDataCounters::MergeRequestCounter.count(:create)
       link_lfs_objects(issuable)
 

spec/services/merge_requests/after_create_service_spec.rb

@@ -19,27 +19,53 @@ describe MergeRequests::AfterCreateService do
     end
 
     it 'creates a merge request open event' do
-      expect(event_service).to receive(:open_mr).with(merge_request, merge_request.author)
+      expect(event_service)
+        .to receive(:open_mr).with(merge_request, merge_request.author)
 
       after_create_service.execute(merge_request)
     end
 
     it 'creates a new merge request notification' do
-      expect(notification_service).to receive(:new_merge_request).with(merge_request, merge_request.author)
+      expect(notification_service)
+        .to receive(:new_merge_request).with(merge_request, merge_request.author)
 
       after_create_service.execute(merge_request)
     end
 
     it 'writes diffs to the cache' do
-      expect(merge_request).to receive_message_chain(:diffs, :write_cache)
+      expect(merge_request)
+        .to receive_message_chain(:diffs, :write_cache)
 
       after_create_service.execute(merge_request)
     end
 
     it 'creates cross references' do
-      expect(merge_request).to receive(:create_cross_references!).with(merge_request.author)
+      expect(merge_request)
+        .to receive(:create_cross_references!).with(merge_request.author)
 
       after_create_service.execute(merge_request)
     end
+
+    it 'creates a pipeline and updates the HEAD pipeline' do
+      expect(after_create_service)
+        .to receive(:create_pipeline_for).with(merge_request, merge_request.author)
+      expect(merge_request).to receive(:update_head_pipeline)
+
+      after_create_service.execute(merge_request)
+    end
+
+    # https://gitlab.com/gitlab-org/gitlab/issues/208813
+    context 'when the create_merge_request_pipelines_in_sidekiq flag is disabled' do
+      before do
+        stub_feature_flags(create_merge_request_pipelines_in_sidekiq: false)
+      end
+
+      it 'does not create a pipeline or update the HEAD pipeline' do
+        expect(after_create_service).not_to receive(:create_pipeline_for)
+        expect(merge_request).not_to receive(:update_head_pipeline)
+
+        after_create_service.execute(merge_request)
+      end
+    end
   end
 end

spec/services/merge_requests/create_service_spec.rb

@@ -129,7 +129,23 @@ describe MergeRequests::CreateService, :clean_gitlab_redis_shared_state do
         end
       end
 
-      context 'when head pipelines already exist for merge request source branch' do
+      # https://gitlab.com/gitlab-org/gitlab/issues/208813
+      context 'when the create_merge_request_pipelines_in_sidekiq flag is disabled' do
+        before do
+          stub_feature_flags(create_merge_request_pipelines_in_sidekiq: false)
+        end
+
+        it 'creates a pipeline and updates the HEAD pipeline' do
+          expect(service).to receive(:create_pipeline_for)
+          expect_next_instance_of(MergeRequest) do |merge_request|
+            expect(merge_request).to receive(:update_head_pipeline)
+          end
+
+          service.execute
+        end
+      end
+
+      context 'when head pipelines already exist for merge request source branch', :sidekiq_inline do
         let(:shas) { project.repository.commits(opts[:source_branch], limit: 2).map(&:id) }
         let!(:pipeline_1) { create(:ci_pipeline, project: project, ref: opts[:source_branch], project_id: project.id, sha: shas[1]) }
         let!(:pipeline_2) { create(:ci_pipeline, project: project, ref: opts[:source_branch], project_id: project.id, sha: shas[0]) }
@@ -175,7 +191,7 @@ describe MergeRequests::CreateService, :clean_gitlab_redis_shared_state do
         end
       end
 
-      describe 'Pipelines for merge requests' do
+      describe 'Pipelines for merge requests', :sidekiq_inline do
         before do
           stub_ci_pipeline_yaml_file(YAML.dump(config))
         end
@@ -216,7 +232,9 @@ describe MergeRequests::CreateService, :clean_gitlab_redis_shared_state do
               target_project.add_maintainer(user)
             end
 
-            it 'create legacy detached merge request pipeline for fork merge request', :sidekiq_might_not_need_inline do
+            it 'create legacy detached merge request pipeline for fork merge request' do
+              merge_request.reload
+
               expect(merge_request.actual_head_pipeline)
                 .to be_legacy_detached_merge_request_pipeline
             end
@@ -228,6 +246,8 @@ describe MergeRequests::CreateService, :clean_gitlab_redis_shared_state do
             end
 
             it 'create legacy detached merge request pipeline for non-fork merge request' do
+              merge_request.reload
+
               expect(merge_request.actual_head_pipeline)
                 .to be_legacy_detached_merge_request_pipeline
             end
@@ -262,6 +282,8 @@ describe MergeRequests::CreateService, :clean_gitlab_redis_shared_state do
             end
 
             it 'sets the latest detached merge request pipeline as the head pipeline' do
+              merge_request.reload
+
               expect(merge_request.actual_head_pipeline).to be_merge_request_event
             end
           end