Abstract
In this chapter our survey of methods and structures for application-level fault-tolerance continues, getting closer to the programming language: Indeed, tools such as compilers and translators work at the level of the language—they parse, interpret, compile or transform our programs, so they are interesting candidates for managing dependability aspects in the application layer. An important property of this family of methods is the fact that fault-tolerance complexity is extracted from the program and turned into architectural complexity in the compiler or the translator. Apart from continuing with our survey, this chapter also aims at providing the reader with two practical examples: • Reflective and refractive variables, that is, a syntactical structure to express adaptive feedback loops in the application layer. This is useful to resilient computing because a feedback loop can attach error recovery strategies to error detection events. • Redundant variables, that is, a tool that allows designers to make use of adaptively redundant data structures with commodity programming languages such as C or Java. Designers using such tools can define redundant data structures in which the degree of redundancy is not fixed once and for all at design time, but rather it changes dynamically with respect to the disturbances experienced during the run time. Both tools are new research activities that are currently being carried out by the author of this book at the PATS research group of the University of Antwerp. It is shown how through a simple translation approach it is possible to provide sophisticated features such as adaptive fault-tolerance to programs written in any language, even plain old C.
TopIntroduction And Objectives
In this chapter our survey of methods and structures for application-level fault-tolerance continues, getting closer to the programming language: Indeed, tools such as compilers and translators work at the level of the language—they parse, interpret, compile or transform our programs, so they are interesting candidates for managing dependability aspects in the application layer. An important property of this family of methods is the fact that fault-tolerance complexity is extracted from the program and turned into architectural complexity in the compiler or the translator.Apart from continuing with our survey, this chapter also aims at providing the reader with two practical examples:
- •
Reflective and refractive variables, that is, a syntactical structure to express adaptive feedback loops in the application layer. This is useful to resilient computing because a feedback loop can attach error recovery strategies to error detection events.
- •
Redundant variables, that is, a tool that allows designers to make use of adaptively redundant data structures with commodity programming languages such as C or Java. Designers using such tools can define redundant data structures in which the degree of redundancy is not fixed once and for all at design time, but rather it changes dynamically with respect to the disturbances experienced during the run time.
Both tools are new research activities that are currently being carried out by the author of this book at the PATS research group of the University of Antwerp. It is shown how through a simple translation approach it is possible to provide sophisticated features such as adaptive fault-tolerance to programs written in any language, even plain old C.
TopFault-Tolerant Protocols Using Compilers And Translators
Our first subject is tools that work “within” the compiler: Meta-object protocols. Most of such tools are based on the concept of reflection: The ability to mirror the feature of a system by creating a causal connection between sub-systems and internal objects. In other words, events experienced by a reflected sub-system trigger events on the object representing that sub-system, and vice-versa.