    # File lib/phusion_passenger/abstract_server_collection.rb, line 170
            def delete(key)
                    raise ArgumentError, "cleanup() has already been called." if @done
                    must_be_in_synchronize_block
                    server = @collection[key]
                    if server
                            if server.started?
                                    server.stop
                            end
                            @collection.delete(key)
                            if server.next_cleaning_time == @next_cleaning_time
                                    @next_cleaning_time = nil
                            end
                    end
            end