Giuliano Losa

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Data stream processing applications are often expressed as data flow graphs, composed of operators connected via streams. This structured representation provides a simple yet powerful paradigm for building large-scale, distributed, high-performance applications. However, there are many tasks that require sharing data across operators, and across operators(More)
New multi-leader consensus protocols leverage the Generalized Consensus specification to enable low latency, even load balancing, and high parallelism. However, these protocols introduce inherent costs with significant performance impact: they need quorums bigger than the minimum required to solve consensus and need to track dependency relations among(More)
We define the Abortable Linearizable Module automaton (ALM for short) and prove its key composition property using the IOA theory of HOLCF. The ALM is at the heart of the Speculative Linearizabil-ity framework. This framework simplifies devising correct speculative algorithms by enabling their decomposition into independent modules that can be analyzed and(More)
Leaderless consensus algorithms in the vein of EPaxos have performance advantages, especially for geo-replication, but are also very intricate, making them hard to modify and adapt for specific use cases. In this paper we show that their core principle can be captured in a generic leaderless generalized-consensus algorithm that uses two new abstractions: a(More)
Decades of research in distributed computing have led to a variety of perspectives on what it means for a concurrent algorithm to be efficient, depending on model assumptions, progress guarantees, and complexity metrics. It is therefore natural to ask whether one could compose algorithms that perform efficiently under different conditions, so that the(More)
Suisse 2012 PAR Aleksandar Dragojević To Marija for all her love and support. Acknowledgements I would first like to thank my thesis supervisor Rachid Guerraoui without whose advice and guidance this thesis would not have been written. I also thank the president of the jury André Schiper and the members of the jury Tim Harris, Pascal Felber, and Viktor(More)
—This paper proposes CAESAR, a novel multi-leader Generalized Consensus protocol for geographically replicated sites. The main goal of CAESAR is to overcome one of the major limitations of existing approaches, which is the significant performance degradation when application workload produces conflicting requests. CAESAR does that by changing the way a fast(More)
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