Patterns for Measuring Performance-Related QoS Properties in Distributed Systems
Ernst Oberortner, Uwe Zdun, Schahram Dustdar · 2010
In distributed systems, clients can access a server’s objects via a network. Service Level Agreements (SLA) can exist, which specify – among other things – performance-related Quality of Service (QoS) properties between the client and the server, such as round-trip time, processing time, or availability. For a provider, i.e., the server’s host, serious financial consequences or other penalties can follow in case of not fulfilling the SLAs. The consumer, i.e., the client, wants to evaluate that the provider complies with the guaranteed SLAs. Designing and developing a QoSaware distributed system means facing many design challenges, such as where and how to measure the performance-related QoS properties. This paper presents design practices and patterns for measuring such QoS properties by extending existing patterns. The pattern’s implementations are exemplified in a web service-oriented distributed system. The focus of the pattern lies on the QoS measuring impact on the client’s or server’s performance, the extend of separation of concerns, the property of reusability, the preciseness of the measured QoS properties, and the vulnerability to forgery by the server or the client. This paper’s patterns should help software architects and developers in building an efficient solution for measuring performance-related QoS properties in a distributed system. 1