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About

Nuno Machado is a post-doctoral researcher at the High-Assurance Software Laboratory (HASLab) of University of Minho and INESC TEC.

His current research focuses on designing scalable and resilient distributed systems for storing and analyzing massive amounts of data.  He also works/has interest on privacy-aware solutions for cloud computing and IoT.

 

Nuno got a Ph.D. in Computer Science and Engineering from Instituto Superior Técnico (University of Lisbon), under the supervision of Luís Rodrigues. He worked on automated debugging techniques for multithreaded applications that allow developers to deterministically replay concurrency bugs, as well as isolate their root cause.

 

In the summer of 2014, Nuno was an intern at Microsoft Research (Redmond), working with Brandon Lucia on concurrency debugging.

Interest
Topics
Details

Details

  • Name

    Nuno Almeida Machado
  • Role

    External Research Collaborator
  • Since

    13th July 2016
  • Nationality

    Portugal
  • Contacts

    +351253604440
    nuno.a.machado@inesctec.pt
001
Publications

2019

Minha: Large-scale distributed systems testing made practical

Authors
Machado, N; Maia, F; Neves, F; Coelho, F; Pereira, J;

Publication
Leibniz International Proceedings in Informatics, LIPIcs

Abstract
Testing large-scale distributed system software is still far from practical as the sheer scale needed and the inherent non-determinism make it very expensive to deploy and use realistically large environments, even with cloud computing and state-of-the-art automation. Moreover, observing global states without disturbing the system under test is itself difficult. This is particularly troubling as the gap between distributed algorithms and their implementations can easily introduce subtle bugs that are disclosed only with suitably large scale tests. We address this challenge with Minha, a framework that virtualizes multiple JVM instances in a single JVM, thus simulating a distributed environment where each host runs on a separate machine, accessing dedicated network and CPU resources. The key contributions are the ability to run off-the-shelf concurrent and distributed JVM bytecode programs while at the same time scaling up to thousands of virtual nodes; and enabling global observation within standard software testing frameworks. Our experiments with two distributed systems show the usefulness of Minha in disclosing errors, evaluating global properties, and in scaling tests orders of magnitude with the same hardware resources. © Nuno Machado, Francisco Maia, Francisco Neves, Fábio Coelho, and José Pereira; licensed under Creative Commons License CC-BY 23rd International Conference on Principles of Distributed Systems (OPODIS 2019).

2019

Concurrency Debugging with MaxSMT

Authors
Terra Neves, M; Machado, N; Lynce, I; Manquinho, V;

Publication
THIRTY-THIRD AAAI CONFERENCE ON ARTIFICIAL INTELLIGENCE / THIRTY-FIRST INNOVATIVE APPLICATIONS OF ARTIFICIAL INTELLIGENCE CONFERENCE / NINTH AAAI SYMPOSIUM ON EDUCATIONAL ADVANCES IN ARTIFICIAL INTELLIGENCE

Abstract
Current Maximum Satisfiability (MaxSAT) algorithms based on successive calls to a powerful Satisfiability (SAT) solver are now able to solve real-world instances in many application domains. Moreover, replacing the SAT solver with a Satisfiability Modulo Theories (SMT) solver enables effective MaxSMT algorithms. However, MaxSMT has seldom been used in debugging multi-threaded software. Multi-threaded programs are usually non-deterministic due to the huge number of possible thread operation schedules, which makes them much harder to debug than sequential programs. A recent approach to isolate the root cause of concurrency bugs in multi-threaded software is to produce a report that shows the differences between a failing and a non-failing execution. However, since they rely solely on heuristics, these reports can be unnecessarily large. Hence, reports may contain operations that are not relevant to the bug's occurrence. This paper proposes the use of MaxSMT for the generation of minimal reports for multi-threaded software with concurrency bugs. The proposed techniques report situations that the existing techniques are not able to identify. Experimental results show that using MaxSMT can significantly improve the accuracy of the generated reports and, consequently, their usefulness in debugging the root cause of concurrency bugs.

2018

CoopREP: Cooperative record and replay of concurrency bugs

Authors
Machado, N; Romano, P; Rodrigues, L;

Publication
Software Testing, Verification and Reliability

Abstract

2018

Falcon: A Practical Log-Based Analysis Tool for Distributed Systems

Authors
Neves, F; Machado, N; Pereira, J;

Publication
48th Annual IEEE/IFIP International Conference on Dependable Systems and Networks, DSN 2018, Luxembourg City, Luxembourg, June 25-28, 2018

Abstract
Programmers and support engineers typically rely on log data to narrow down the root cause of unexpected behaviors in dependable distributed systems. Unfortunately, the inherently distributed nature and complexity of such distributed executions often leads to multiple independent logs, scattered across different physical machines, with thousands or millions entries poorly correlated in terms of event causality. This renders log-based debugging a tedious, time-consuming, and potentially inconclusive task. We present Falcon, a tool aimed at making log-based analysis of distributed systems practical and effective. Falcon's modular architecture, designed as an extensible pipeline, allows it to seamlessly combine several distinct logging sources and generate a coherent space-time diagram of distributed executions. To preserve event causality, even in the presence of logs collected from independent unsynchronized machines, Falcon introduces a novel happens-before symbolic formulation and relies on an off-the-shelf constraint solver to obtain a coherent event schedule. Our case study with the popular distributed coordination service Apache Zookeeper shows that Falcon eases the log-based analysis of complex distributed protocols and is helpful in bridging the gap between protocol design and implementation. © 2018 IEEE.

2018

Totally Ordered Replication for Massive Scale Key-Value Stores

Authors
Ribeiro, J; Machado, N; Maia, F; Matos, M;

Publication
Distributed Applications and Interoperable Systems - 18th IFIP WG 6.1 International Conference, DAIS 2018, Held as Part of the 13th International Federated Conference on Distributed Computing Techniques, DisCoTec 2018, Madrid, Spain, June 18-21, 2018, Proceedings

Abstract