A Transient Overload Generator forWeb Servers

Transient overload is a short term event characterized by a sudden and unexpected rise of the arrival rate in a Web server. Transient overload events in Web servers have been observed more frequently as the number of Internet users grows and the Web services become more popular. This paper deals with the non-trivial problem of generating overload for Web server testing. In this paper we present a new Web server workload generator called TORO, which is able to overload a Web server based on the maximum effective capacity of the server. The load generator TORO allows the usage of both real and synthetic loads. The results show that the load generator is able to deliver thousands of requests per second in a variety of workload patterns. Additionally, this paper presents an evaluation of the Apache HTTP Server under transient overload events. The results can be applied to the design of new Web servers.