Generic and Efficient Program Monitoring by trace analysis

E. Jahier and M. Ducass'e "Generic Program Monitoring by Trace Analysis" in the Theory and Practice of Logic Programming journal, Volume 2 part 4&5, pp 613-645, September 2002, Special Issue Program Development, Cambridge University Press Program execution monitoring consists of checking whole executions for given properties in order to collect global run-time information. Monitoring is very useful to maintain programs. However, application developers face the following dilemma: either they use existing tools which never exactly fit their needs, or they invest a lot of effort to implement monitoring code. In this article we argue that, when an event-oriented tracer exists, the compiler developers can enable the application developers to easily code their own, relevant, monitors which will run efficiently. We propose a high-level operator, called foldt, which operates on execution traces. One of the key advantages of our approach is that it allows a clean separation of concerns; the definition of monitors is neither intertwined in the user source code nor in the language compiler. We give a number of applications of the foldt operator to compute monitors for Mercury program executions: execution profiles, graphical abstract views, and two test coverage measurements. Each example is implemented by a few simple lines of Mercury. Detailed measurements show acceptable performance of the basic mechanism of foldt for executions of several millions of execution events.