Andrew Tjang

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In this paper, we propose a management framework for protecting large computer systems against operator mistakes. By detecting and confining mistakes to isolated portions of the managed system, our framework facilitates correct operation even by inexperienced operators. We built a prototype management system called Barricade based on our framework. We(More)
Operator mistakes are a significant source of unavailability in Internet services. In our previous work, we proposed operator action validation as an approach for detecting mistakes while hiding them from the service and its users. Previous validation strategies have limitations, however, including the need for instances of correct behavior for comparison.(More)
In this work, we explore active tapes, a novel sensor network architecture. An active tape is a sequence of sensor nodes and related units (such as batteries) organized around a bus. A bus of programmable sensor nodes is, in effect, a programmable linear array, thus the term active tape. A bus provides a simple mechanism to share resources. In a sensor(More)
Operator mistakes have been identified as a significant source of unavailability in Internet services. In this paper, we propose a new language, A, for service engineers to write assertions about expected behaviors, proper configurations, and proper structural characteristics. This formalized specification of correct behavior can be used to bolster system(More)
Distributed system fault detection and analysis has, until recently, focused on building passive monitoring tools without any system level knowledge. It is only now that new approaches, such as instrumenting the software used in the system to collect data about request path, have been used. In this paper we present a new monitoring and fault detection tool(More)
With the number of Computer Science (CS) jobs on the rise, there is a greater need for Computer Science graduates than ever. At the same time, most CS departments across the country are only seeing 25-30% of female students in their classes, meaning that we are failing to draw interest from a large portion of the population. In this work, we explore the(More)
Online services are rapidly becoming the supporting infrastructure for numerous users' work and leisure, placing higher demands on their availability and correct functioning. Increasingly, these services are comprised of complex conglomerates of distributed hardware and software components. Added to this complexity, these services evolve quite frequently(More)
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