Many of today’s software systems are parallel or concurrent. With the rise of Node.js and more generally event-loop architectures, many systems need to handle concurrency. However, its non-deterministic behavior makes it hard to reproduce bugs. Today’s interactive debuggers unfortunately do not support developers in debugging non-deterministic issues. They only allow us to explore a single execution path. Therefore, some bugs may never be reproduced in the debugging session, because the right conditions are not triggered. As a solution, we propose multiverse debugging, a new approach for debugging non-deterministic programs that allows developers to observe all possible execution paths of a parallel program and debug it interactively. We introduce the concepts of multiverse breakpoints and stepping, which can halt a program in different execution paths, i.e. universes. We apply multiverse debugging to AmbientTalk, an actor-based language, resulting in Voyager, a multiverse debugger implemented on top of the AmbientTalk operational semantics. We provide a proof of non-interference, i.e., we prove that observing the behavior of a program by the debugger does not affect the behavior of that program and vice versa. Multiverse debugging establishes the foundation for debugging non-deterministic programs interactively, which we believe can aid the development of parallel and concurrent systems.
@InProceedings{torreslopez_et_al:LIPIcs.ECOOP.2019.27, author = {Torres Lopez, Carmen and Gurdeep Singh, Robbert and Marr, Stefan and Gonzalez Boix, Elisa and Scholliers, Christophe}, title = {{Multiverse Debugging: Non-Deterministic Debugging for Non-Deterministic Programs}}, booktitle = {33rd European Conference on Object-Oriented Programming (ECOOP 2019)}, pages = {27:1--27:30}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-111-5}, ISSN = {1868-8969}, year = {2019}, volume = {134}, editor = {Donaldson, Alastair F.}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2019.27}, URN = {urn:nbn:de:0030-drops-108192}, doi = {10.4230/LIPIcs.ECOOP.2019.27}, annote = {Keywords: Debugging, Parallelism, Concurrency, Actors, Formal Semantics} }
Feedback for Dagstuhl Publishing