Remove FF merge_trains_parallel_pipelines

This commit also removes merge_trains_high_concurrency,
merge_trains_medium_concurrency

ee/app/services/merge_trains/refresh_merge_requests_service.rb

@@ -4,10 +4,7 @@ module MergeTrains
     include ::Gitlab::ExclusiveLeaseHelpers
     include ::Gitlab::Utils::StrongMemoize
 
-    HIGH_CONCURRENCY = 20
-    MEDIUM_CONCURRENCY = 10
-    LOW_CONCURRENCY = 4
-    NO_CONCURRENCY = 1
+    DEFAULT_CONCURRENCY = 20
 
     ##
     # merge_request ... A merge request pointer in a merge train.
@@ -56,17 +53,7 @@ module MergeTrains
 
     def max_concurrency
       strong_memoize(:max_concurrency) do
-        if Feature.enabled?(:merge_trains_parallel_pipelines, project, default_enabled: true)
-          if Feature.enabled?(:merge_trains_high_concurrency, project, default_enabled: true)
-            HIGH_CONCURRENCY
-          elsif Feature.enabled?(:merge_trains_medium_concurrency, project)
-            MEDIUM_CONCURRENCY
-          else
-            LOW_CONCURRENCY
-          end
-        else
-          NO_CONCURRENCY
-        end
+        DEFAULT_CONCURRENCY
       end
     end
   end

ee/changelogs/unreleased/remove-ff-merge_trains_parallel_pipelines.yml

+---
+title: Change default concurrency of merge trains to twenty
+merge_request: 30599
+author:
+type: changed

ee/spec/services/merge_trains/refresh_merge_requests_service_spec.rb

@@ -55,19 +55,6 @@ describe MergeTrains::RefreshMergeRequestsService do
         subject
       end
 
-      context 'when merge_trains_parallel_pipelines feature flag is disabled' do
-        before do
-          stub_feature_flags(merge_trains_parallel_pipelines: false)
-        end
-
-        it 'does not refresh merge request 2' do
-          expect(refresh_service_1).to receive(:execute).with(merge_request_1)
-          expect(refresh_service_2).not_to receive(:execute).with(merge_request_2)
-
-          subject
-        end
-      end
-
       context 'when refresh service 1 returns error status' do
         let(:refresh_service_1_result) { { status: :error, message: 'Failed to create ref' } }
 
@@ -186,60 +173,4 @@ describe MergeTrains::RefreshMergeRequestsService do
       end
     end
   end
-
-  describe '#max_concurrency' do
-    subject { service.send(:max_concurrency) }
-
-    context 'when `merge_trains_parallel_pipelines` feature flag is enabled' do
-      before do
-        stub_feature_flags(merge_trains_parallel_pipelines: true)
-      end
-
-      context 'when `merge_trains_high_concurrency` feature flag is enabled' do
-        before do
-          stub_feature_flags(merge_trains_high_concurrency: true)
-        end
-
-        it 'returns high concurrency' do
-          is_expected.to eq(described_class::HIGH_CONCURRENCY)
-        end
-      end
-
-      context 'when `merge_trains_high_concurrency` feature flag is disabled' do
-        before do
-          stub_feature_flags(merge_trains_high_concurrency: false)
-        end
-
-        context 'when `merge_trains_medium_concurrency` feature flag is enabled' do
-          before do
-            stub_feature_flags(merge_trains_medium_concurrency: true)
-          end
-
-          it 'returns medium concurrency' do
-            is_expected.to eq(described_class::MEDIUM_CONCURRENCY)
-          end
-        end
-
-        context 'when `merge_trains_medium_concurrency` feature flag is disabled' do
-          before do
-            stub_feature_flags(merge_trains_medium_concurrency: false)
-          end
-
-          it 'returns low concurrency' do
-            is_expected.to eq(described_class::LOW_CONCURRENCY)
-          end
-        end
-      end
-    end
-
-    context 'when `merge_trains_parallel_pipelines` feature flag is disabled' do
-      before do
-        stub_feature_flags(merge_trains_parallel_pipelines: false)
-      end
-
-      it 'returns no concurrency' do
-        is_expected.to eq(described_class::NO_CONCURRENCY)
-      end
-    end
-  end
 end