Do not save user preferences on read-only mode

app/controllers/concerns/issuable_collections.rb

@@ -126,6 +126,8 @@ module IssuableCollections
     sort_param = params[:sort]
     sort_param ||= user_preference[issuable_sorting_field]
 
+    return sort_param if Gitlab::Database.read_only?
+
     if user_preference[issuable_sorting_field] != sort_param
       user_preference.update_attribute(issuable_sorting_field, sort_param)
     end

spec/controllers/projects/issues_controller_spec.rb

@@ -42,6 +42,8 @@ describe Projects::IssuesController do
 
       it_behaves_like "issuables list meta-data", :issue
 
+      it_behaves_like 'set sort order from user preference'
+
       it "returns index" do
         get :index, namespace_id: project.namespace, project_id: project
 

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -160,6 +160,8 @@ describe Projects::MergeRequestsController do
 
     it_behaves_like "issuables list meta-data", :merge_request
 
+    it_behaves_like 'set sort order from user preference'
+
     context 'when page param' do
       let(:last_page) { project.merge_requests.page().total_pages }
       let!(:merge_request) { create(:merge_request_with_diffs, target_project: project, source_project: project) }

spec/support/shared_examples/controllers/set_sort_order_from_user_preference_shared_examples.rb

+shared_examples 'set sort order from user preference' do
+  describe '#set_sort_order_from_user_preference' do
+    # There is no issuable_sorting_field defined in any CE controllers yet,
+    # however any other field present in user_preferences table can be used for testing.
+    let(:sorting_field) { :issue_notes_filter }
+    let(:sorting_param) { 'any' }
+
+    before do
+      allow(controller).to receive(:issuable_sorting_field).and_return(sorting_field)
+    end
+
+    context 'when database is in read-only mode' do
+      it 'it does not update user preference' do
+        allow(Gitlab::Database).to receive(:read_only?).and_return(true)
+
+        expect_any_instance_of(UserPreference).not_to receive(:update_attribute).with(sorting_field, sorting_param)
+
+        get :index, namespace_id: project.namespace, project_id: project, sort: sorting_param
+      end
+    end
+
+    context 'when database is not in read-only mode' do
+      it 'updates user preference' do
+        allow(Gitlab::Database).to receive(:read_only?).and_return(false)
+
+        expect_any_instance_of(UserPreference).to receive(:update_attribute).with(sorting_field, sorting_param)
+
+        get :index, namespace_id: project.namespace, project_id: project, sort: sorting_param
+      end
+    end
+  end
+end