A synthetic workload generation technique for stress testing session-based systems

Enterprise applications are often business critical but lack effective synthetic workload generation techniques to evaluate performance. These workloads are characterized by sessions of interdependent requests that often cause and exploit dynamically generated responses. Interrequest dependencies must be reflected in synthetic workloads for these systems to exercise application functions correctly. This poses significant challenges for automating the construction of representative synthetic workloads and manipulating workload characteristics for sensitivity analyses. This paper presents a technique to overcome these problems. Given request logs for a system under study, the technique automatically creates a synthetic workload that has specified characteristics and maintains the correct interrequest dependencies. The technique is demonstrated through a case study involving a TPC-W e-commerce system. Results show that incorrect performance results can be obtained by neglecting interrequest dependencies, thereby highlighting the value of our technique. The study also exploits our technique to investigate the impact of several workload characteristics on system performance. Results establish that high variability in the distributions of session length, session idle times, and request service times can cause increased contention among sessions, leading to poor system responsiveness. To the best of our knowledge, these are the first results of this kind for a session-based system. We believe our technique is of value for studies where fine control over workload is essential

Effects of sugars and aminooxyacetic acid on the longevity of pollinated Oncidium Gower Ramsey flowers

The effects of sugars and aminooxyacetic acid (AOA) on the vase life of pollinated Oncidium Gower Ramsey flowers were investigated in this study. AOA was found to be an effective ethylene inhibitor as holding solutions containing 0.5 mM of AOA considerably prolonged the vase life of the flowers. The best treatment in delaying the senescence of pollinated Oncidium Gower Ramsey flowers were solutions of 4 sucrose + 0.5 mM AOA and 0.5 mM AOA. Both these treatments managed to delay the discolouration, furrowing and appearance of the veins up to nearly twice the length of time it took for the control flowers held in distilled water, to start senescing. The addition of glucose to the holding solution was not as effective as sucrose in delaying the senescence and prolonging the vase life of the flowers. Signs of senescence such as discolouration were measured using the Minolta chroma meter. Weight loss and pH of the holding solutions were also measured daily. AOA added in the solutions had a positive effect of lowering the pH of the holding solution thus inhibiting bacterial growth in the vial. A low pH also accounted for better water uptake by the flowers which delayed turgor loss and thus also delaying the wilting of the flowers

Integrating performance modeling in the software development process

We discuss the integration of performance modeling and analysis in the software development process. Various approaches have been recently defined to integrate performance models and specification languages and models to derive or validate non-functional properties of a software system. Such integration of quantitative performance analysis should provide feedback easily understandable by the software designer and system developers. A framework that allows the combination of different performance modeling techniques and methods, defined at different levels of abstraction, should better support performance analysis and validation of complex and heterogeneous software systems during the software development process

KlaperSuite: an integrated model-driven environment for reliability and performance analysis of component-based systems

Automatic prediction tools play a key role in enabling the application of non-functional requirements analysis to selection and assembly of components for Component-Based Systems, reducing the need for strong mathematical skills to software designers. Exploiting the paradigm of Model Driven Engineering (MDE), it is possible to automate transformations from design models to analytical models, enabling for formal property verification. MDE is the core paradigm of KlaperSuite presented in this paper, which exploits the KLAPER pivot language to fill the gap between Design and Analysis of Component-Based Systems for reliability and performance properties. KlaperSuite is a family of tools empowering designers with the ability to capture and analyze QoS views of their systems by building a one-click bridge towards a number of established verification instruments