Add migration mode for db migrations

Can be executed with `bundle exec rake db:migrate WITH_BENCHMARK=true`

Author: johha

lib/cloud_controller/db_migrator.rb

@@ -29,7 +29,25 @@ def initialize(db, max_migration_duration_in_minutes=nil, max_migration_statemen
   def apply_migrations(opts={})
     Sequel.extension :migration
     require 'vcap/sequel_case_insensitive_string_monkeypatch'
-    Sequel::Migrator.run(@db, SEQUEL_MIGRATIONS, opts)
+
+    if ENV.fetch('WITH_BENCHMARK', false)
+      # rubocop:disable Rails/Output
+      puts('######################################')
+      puts('# Starting migrations with benchmark #')
+      puts('######################################')
+      require 'benchmark'
+      bm_output = Benchmark.measure { Sequel::Migrator.run(@db, SEQUEL_MIGRATIONS, opts) }
+      puts('###########')
+      puts('# Results #')
+      puts('###########')
+      puts("Total time for all migrations: #{bm_output.total} seconds")
+      puts("System time for all migrations: #{bm_output.stime} seconds")
+      puts("User time for all migrations: #{bm_output.utime} seconds")
+      puts("Real time for all migrations: #{bm_output.real} seconds")
+      # rubocop:enable Rails/Output
+    else
+      Sequel::Migrator.run(@db, SEQUEL_MIGRATIONS, opts)
+    end
   end
 
   def rollback(number_to_rollback)

spec/unit/lib/cloud_controller/db_migrator_spec.rb

@@ -76,4 +76,22 @@
       DBMigrator.new(db, nil, nil, 1234)
     end
   end
+
+  describe 'benchmark' do
+    let(:migrator) { DBMigrator.new(db) }
+
+    it 'runs migrations without benchmark' do
+      expect(Benchmark).not_to receive(:measure)
+      migrator.apply_migrations
+    end
+
+    context 'when setting WITH_BENCHMARK env' do
+      before { ENV['WITH_BENCHMARK'] = 'true' }
+
+      it 'runs migrations with benchmark' do
+        expect(Benchmark).to receive(:measure).and_return(double(:bm_output, total: 1, stime: 2, utime: 3, real: 4))
+        expect { migrator.apply_migrations }.to output(/Starting migrations with benchmark/).to_stdout
+      end
+    end
+  end
 end