message_pack_pool

# File activesupport/lib/active_support/message_pack/serializer.rb, line 47
        def message_pack_pool
          @message_pack_pool ||= begin
            unless message_pack_factory.frozen?
              Extensions.install(message_pack_factory)
              install_unregistered_type_handler
              message_pack_factory.freeze
            end
            message_pack_factory.pool(ENV.fetch("RAILS_MAX_THREADS", 5).to_i)
          end
        end