The Fast and the Fair: A Fault-Injection-Driven Comparison of Restart Oracles for Reliable Web Services

Web services are typically deployed in Internet or Intranet environments, making message transfers susceptible to a wide variety of network, protocol and system failures. To mitigate these problems, reliable messaging solutions for Web services have been proposed that retry messages suspected to be lost. It is of interest to evaluate the performance of such reliable messaging solutions, and in this paper we therefore utilise a newly developed fault-injection environment for the analysis of time-out strategies for the Web services reliable messaging standard. We compare oracles that determine retransmission times with respect to the tradeoff between two metrics: the effective transfer time and the overhead in terms of additional message transmissions. Our fault-injection environment allows faults to be invoked in the IP layer, representing a variety of failure situations in the underlying system. The study presented in this paper includes two adaptive oracles, which set the length of the retransmission interval based on round trip time measurements, and two static oracles. The study considers both HTTP and Mail as SOAP transports. We conclude that adaptive oracles may significantly outperform static oracles when the underlying system exhibits more complex behaviour