1 files changed, 78 insertions, 0 deletions
diff --git a/spec/services/loose_foreign_keys/batch_cleaner_service_spec.rb b/spec/services/loose_foreign_keys/batch_cleaner_service_spec.rb
index d3d57ea2444..538d9638879 100644
--- a/spec/services/loose_foreign_keys/batch_cleaner_service_spec.rb
+++ b/spec/services/loose_foreign_keys/batch_cleaner_service_spec.rb
@@ -115,4 +115,82 @@ RSpec.describe LooseForeignKeys::BatchCleanerService do
       expect(loose_fk_child_table_2.where(parent_id_with_different_column: other_parent_record.id).count).to eq(2)
     end
   end
+
+  describe 'fair queueing' do
+    context 'when the execution is over the limit' do
+      let(:modification_tracker) { instance_double(LooseForeignKeys::ModificationTracker) }
+      let(:over_limit_return_values) { [true] }
+      let(:deleted_record) { LooseForeignKeys::DeletedRecord.load_batch_for_table('public._test_loose_fk_parent_table', 1).first }
+      let(:deleted_records_rescheduled_counter) { Gitlab::Metrics.registry.get(:loose_foreign_key_rescheduled_deleted_records) }
+      let(:deleted_records_incremented_counter) { Gitlab::Metrics.registry.get(:loose_foreign_key_incremented_deleted_records) }
+
+      let(:cleaner) do
+        described_class.new(parent_table: '_test_loose_fk_parent_table',
+                            loose_foreign_key_definitions: loose_foreign_key_definitions,
+                            deleted_parent_records: LooseForeignKeys::DeletedRecord.load_batch_for_table('public._test_loose_fk_parent_table', 100),
+                            modification_tracker: modification_tracker
+                           )
+      end
+
+      before do
+        parent_record_1.delete
+        allow(modification_tracker).to receive(:over_limit?).and_return(*over_limit_return_values)
+        allow(modification_tracker).to receive(:add_deletions)
+      end
+
+      context 'when the deleted record is under the maximum allowed cleanup attempts' do
+        it 'updates the cleanup_attempts column', :aggregate_failures do
+          deleted_record.update!(cleanup_attempts: 1)
+
+          cleaner.execute
+
+          expect(deleted_record.reload.cleanup_attempts).to eq(2)
+          expect(deleted_records_incremented_counter.get(table: loose_fk_parent_table.table_name, db_config_name: 'main')).to eq(1)
+        end
+
+        context 'when the deleted record is above the maximum allowed cleanup attempts' do
+          it 'reschedules the record', :aggregate_failures do
+            deleted_record.update!(cleanup_attempts: LooseForeignKeys::BatchCleanerService::CLEANUP_ATTEMPTS_BEFORE_RESCHEDULE + 1)
+
+            freeze_time do
+              cleaner.execute
+
+              expect(deleted_record.reload).to have_attributes(
+                cleanup_attempts: 0,
+                consume_after: 5.minutes.from_now
+              )
+              expect(deleted_records_rescheduled_counter.get(table: loose_fk_parent_table.table_name, db_config_name: 'main')).to eq(1)
+            end
+          end
+        end
+
+        describe 'when over limit happens on the second cleanup call without skip locked' do
+          # over_limit? is called twice, we test here the 2nd call
+          # - When invoking cleanup with SKIP LOCKED
+          # - When invoking cleanup (no SKIP LOCKED)
+          let(:over_limit_return_values) { [false, true] }
+
+          it 'updates the cleanup_attempts column' do
+            expect(cleaner).to receive(:run_cleaner_service).twice
+
+            deleted_record.update!(cleanup_attempts: 1)
+
+            cleaner.execute
+
+            expect(deleted_record.reload.cleanup_attempts).to eq(2)
+          end
+        end
+      end
+
+      context 'when the lfk_fair_queueing FF is off' do
+        before do
+          stub_feature_flags(lfk_fair_queueing: false)
+        end
+
+        it 'does nothing' do
+          expect { cleaner.execute }.not_to change { deleted_record.reload.cleanup_attempts }
+        end
+      end
+    end
+  end
 end