Rajesh K. Mansharamani

Recovery from Failures Due to Mandelbugs in IT Systems

Several studies have been carried out on software bugs analysis and classification for life and mission critical systems, which include reproducible bugs called Bohrbugs, and hard to reproduce bugs called Mandelbugs. Although software reliability in IT systems has been studied for years, there are only a few formal analytic models for recovery from Mandelbugs. This paper discusses in detail several real cases of Mandelbugs and presents a simple flowchart which describes the recovery processes implemented in IT systems for a large variety of Mandelbugs. The flowchart is based on more than 10 IT systems that are running in production. The paper then presents a closed-form expression of the mean time to recovery from these bugs. Measures of interest including mean time to recovery and system unavailability are computed. A numerical and parametric sensitivity analysis of the model parameters are carried out. This analysis allows the designer to find out important parameter(s) for the recovery from failures due to Mandelbugs.

Performance Testing: Far from Steady State

The dot com era ushered in a number of industry standard load testing tools. While there is no doubt that these tools have helped improve the quality of IT systems, performance testing in the IT industry is far from steady state. There are still severe gaps between performance test results and production systems performance in IT projects. This paper proposes a number of areas where performance testing needs to improve radically, several of which can be incorporated in to load testing tools. Examples are also provided of simple analytics during single user performance testing to demonstrate the effectiveness of this extra but necessary step in the testing process.

Recovery From Software Failures Caused by Mandelbugs

Software failures are still a major concern in mission- and enterprise-critical contexts, despite significant efforts spent in software testing. In fact, while software testing is effective against easily-reproducible bugs (Bohrbugs), it is considerably less suitable for dealing with bugs that lead to hard-to-reproduce failures (Mandelbugs). On the positive side, the elusive nature of Mandelbugs provides opportunities for failure recovery, which are investigated in this paper. Based on real cases of Mandelbugs in eleven Information Technology (IT) systems running in production, the paper proposes a model that describes the recovery processes in IT systems. It then presents closed-form expressions, and a numerical analysis, of the mean time to recovery, and the software (un)availability. This analysis allows the designer to compare recovery strategies, as well as to determine the parameters having a high influence on the efficacy of recovery from failures caused by Mandelbugs.

Simulating Business Processes - A Review of Tools and Techniques

 Abstract—There is a great need for simulation of dynamic/temporal aspects of business processes. The current standard for modeling business processes is BPMN and in this review, the various techniques and tools that use BPMN for simulation are studied. The review also points to shortcomings in BPMN support for simulation and in the BPM tools claim to support simulation of business processes. We also present a case for general purpose DES tools to widen their scope and create components/plugins to convert BPMN output to DES input. Index Terms—BPM, BPMN; BPD; BPC; simulation; business process; discrete event; operations research; DES; DEVS.

DCPE Rollout: Scaling Performance Engineering Training and Certification across a Very Large Enterprise

Performance engineering is a badly needed skill for implementing and running IT systems, but performance engineers are hard to find in the market. This paper presents our experiences in rolling out training and certification in a first level course on performance engineering across a large enterprise. We present data and lessons learned on the nominations for the rollout, the design and analysis of theory and practical exams, and the methods used to ensure fairness in a rollout spanning hundreds of nominations. We present results that show trainees to perform exceeding well much against conventional wisdom, and we also show how the success of the rollout has led to a number of beneficial initiatives for the company.

RVGEN: a tool for generation of random variates

A number of applications in simulation and software testing require random number generation, both uniform and non-uniform. Although libraries are available for random number generation, there is no user-friendly tool to enable the user to use and build random number generators. This paper presents the RVGEN tool, developed at TRDDC. Using the tool, the software developer can design a random number generator specific to a particular pattern. The tool takes specifications at a high level and also partly in C++, and generates C++ code for a number of user-friendly functions. These include setting and getting of random variate parameters, GUIs for inputting parameters, validation of parameters, parameter input and output from a file, generation of random variate class declarations, generation of seeds for multiple streams, and testing of the random variate generator. The tool provides a number of classical, generalpurpose and empiric distributions by default.