Declarative debugging of concurrent Erlang programs

Despite the growing number of concurrent applications in nowadays systems, debugging concurrent programs remains an open issue due to its intrinsic complexity. In this work, we present a declarative debugger for the concurrent language Erlang. Following the ideas of algorithmic debugging, our tool asks questions to the user about the validity of transitions between those program points that involve message passing, and also about the expected results of the function calls occurred during the computation. The differences between the user answers, which represent the intended behavior of the program, and the actual program execution, allow the debugger to detect the function responsible for the error, and to point out the pieces of source code responsible for the bugs. The proposal is based on a concurrent calculus for Erlang programs, and we show a benchmark that assesses its scalability both in terms of resources usage and considering the number of questions asked to the user and their complexity. Furthermore, we check the usability of our proposal, applying the debugger to the Erlang library poolboy.