Rescue MR Dashboard searches from query timeout

app/controllers/concerns/issuable_collections_action.rb

@@ -2,6 +2,7 @@
 
 module IssuableCollectionsAction
   extend ActiveSupport::Concern
+  include GracefulTimeoutHandling
   include IssuableCollections
   include IssuesCalendar
 
@@ -33,6 +34,10 @@ def merge_requests
     @merge_requests = issuables_collection.page(params[:page])
 
     @issuable_meta_data = Gitlab::IssuableMetadata.new(current_user, @merge_requests).data
+  rescue ActiveRecord::QueryCanceled => exception # rubocop:disable Database/RescueQueryCanceled
+    log_exception(exception)
+
+    @search_timeout_occurred = true
   end
   # rubocop:enable Gitlab/ModuleWithInstanceVariables
 

app/views/dashboard/merge_requests.html.haml

@@ -19,5 +19,7 @@
 
 - if current_user && @no_filters_set
   = render 'shared/dashboard/no_filter_selected'
+- elsif @search_timeout_occurred
+  = render 'shared/dashboard/search_timeout_occurred'
 - else
   = render 'shared/merge_requests'

app/views/shared/dashboard/_search_timeout_occurred.html.haml

+.row.empty-state.text-center
+  .col-12
+    .svg-130.gl-mt-3
+      = image_tag 'illustrations/issue-dashboard_results-without-filter.svg'
+  .col-12
+    .text-content
+      %h4
+        = _("Too many results to display. Edit your search or add a filter.")

locale/gitlab.pot

@@ -44211,6 +44211,9 @@ msgstr ""
 msgid "Too many references. Quick actions are limited to at most %{max_count} user references"
 msgstr ""
+msgid "Too many results to display. Edit your search or add a filter."
+msgstr ""
+
 msgid "Too many users found. Quick actions are limited to at most %{max_count} users"
 msgstr ""

spec/controllers/dashboard_controller_spec.rb

@@ -46,6 +46,37 @@
     describe 'GET merge requests' do
       it_behaves_like 'issuables list meta-data', :merge_request, :merge_requests
       it_behaves_like 'issuables requiring filter', :merge_requests
+
+      context 'when an ActiveRecord::QueryCanceled is raised' do
+        before do
+          allow_next_instance_of(Gitlab::IssuableMetadata) do |instance|
+            allow(instance).to receive(:data).and_raise(ActiveRecord::QueryCanceled)
+          end
+        end
+
+        it 'sets :search_timeout_occurred' do
+          get :merge_requests, params: { author_id: user.id }
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(assigns(:search_timeout_occurred)).to eq(true)
+        end
+
+        context 'rendering views' do
+          render_views
+
+          it 'shows error message' do
+            get :merge_requests, params: { author_id: user.id }
+
+            expect(response.body).to have_content('Too many results to display. Edit your search or add a filter.')
+          end
+        end
+
+        it 'logs the exception' do
+          expect(Gitlab::ErrorTracking).to receive(:track_exception).and_call_original
+
+          get :merge_requests, params: { author_id: user.id }
+        end
+      end
     end
   end