Gautier Berthou

Gautier Berthou

Stockholm, Stockholms län, Sverige
425 följare 413 kontakter

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Erfarenhet

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    Stockholm, Sweden

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    Stockholm, Sweden

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    Stockholm, Sweden

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    Stockholm, Sweden

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    Stockholm, Sweden

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    Grenoble Area, France

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    Grenoble Area, France

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Utbildning

  • Université Grenoble Alpes-bild

    Université Grenoble Alpes

    This Ph.D. focused on information dissemination in computer networks. I studied two aspects of this topic: anonymous communication on Internet with rational nodes and uniform total order broadcast in a computer cluster. Concerning the first aspect, I observed that no anonymous communication protocol is capable of working with rational nodes while scaling existed. Therefore, I proposed RAC, the first anonymous communication protocol functioning with rational nodes and able of scaling. Concerning…

    This Ph.D. focused on information dissemination in computer networks. I studied two aspects of this topic: anonymous communication on Internet with rational nodes and uniform total order broadcast in a computer cluster. Concerning the first aspect, I observed that no anonymous communication protocol is capable of working with rational nodes while scaling existed. Therefore, I proposed RAC, the first anonymous communication protocol functioning with rational nodes and able of scaling. Concerning the second aspect, I observed that no existing uniform total order broadcast protocol is capable of ensuring both a good latency and an optimal throughput. In order to fill this lack I proposed FastCast, the first uniform total order broadcast ensuring both an optimal throughput and a low latency.

  • Aktiviteter och föreningar:PromenadorQuestern

  • Aktiviteter och föreningar:grand cercle 2007-2008

    TOFL (ibt) : 95/120

  • Aktiviteter och föreningar:grand cercle 2007-2008

    ENSIMAG
    TOFL (ibt) : 95/120

Publikationer

  • A digital nervous system aiming toward personalized IoT healthcare

    Nature Scientific reports

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  • HopsFS-S3: Extending Object Stores with POSIX-like Semantics and more

    In Proccedings of the 21st International Middleware Conference Industrial Track

    Object stores have become the de-facto platform for storage in the cloud due to their scalability, high availability, and low cost. However, they provide weaker metadata semantics and lower performance compared to distributed hierarchical file systems. In this paper, we introduce HopsFS-S3, a hybrid distributed hierarchical file system backed by an object store while preserving the file system's strong consistency semantics. We base our implementation on HopsFS, a next-generation distribution…

    Object stores have become the de-facto platform for storage in the cloud due to their scalability, high availability, and low cost. However, they provide weaker metadata semantics and lower performance compared to distributed hierarchical file systems. In this paper, we introduce HopsFS-S3, a hybrid distributed hierarchical file system backed by an object store while preserving the file system's strong consistency semantics. We base our implementation on HopsFS, a next-generation distribution of HDFS with distributed metadata. We redesigned HopsFS' block storage layer to transparently use an object store to store the file's blocks without sacrificing the file system's semantics. We also introduced a new block caching service to leverage faster NVMe storage for hot blocks. In our experiments, we show that HopsFS-S3 outperforms EMRFS for IO-bound workloads, with up to 20% higher performance and delivers up to 3 AX the aggregated read throughput of EMRFS. Moreover, we demonstrate that metadata operations on HopsFS-S3 (such as directory rename) are up to two orders of magnitude faster than EMRFS. Finally, HopsFS-S3 opens up the currently closed metadata in object stores, enabling correctly-ordered change notifications with HopsFS' change data capture (CDC) API and customized extensions to metadata.

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  • Hopsworks: Improving user experience and development on hadoop with scalable, strongly consistent metadata

    In Proccedings of the IEEE 37th International Conference on Distributed Computing Systems (ICDCS)

    Hadoop is a popular system for storing, managing,and processing large volumes of data, but it has bare-bonesinternal support for metadata, as metadata is a bottleneck andless means more scalability. The result is a scalable platform withrudimentary access control that is neither user- nor developer-friendly. Also, metadata services that are built on Hadoop, suchas SQL-on-Hadoop, access control, data provenance, and datagovernance are necessarily implemented as eventually consistentservices…

    Hadoop is a popular system for storing, managing,and processing large volumes of data, but it has bare-bonesinternal support for metadata, as metadata is a bottleneck andless means more scalability. The result is a scalable platform withrudimentary access control that is neither user- nor developer-friendly. Also, metadata services that are built on Hadoop, suchas SQL-on-Hadoop, access control, data provenance, and datagovernance are necessarily implemented as eventually consistentservices, resulting in increased development effort and morebrittle software. In this paper, we present a new project-based multi-tenancymodel for Hadoop, built on a new distribution of Hadoopthat provides a distributed database backend for the HadoopDistributed Filesystem's (HDFS) metadata layer. We extendHadoop's metadata model to introduce projects, datasets, andproject-users as new core concepts that enable a user-friendly, UI-driven Hadoop experience. As our metadata service is backed bya transactional database, developers can easily extend metadataby adding new tables and ensure the strong consistency ofextended metadata using both transactions and foreign keys.

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  • Leader election using NewSQL database systems

    In Proccedings of the IFIP International Conference on Distributed Applications and Interoperable Systems

    Leader election protocols are a fundamental building block for replicated distributed services. They ease the design of leader-based coordination protocols that tolerate failures. In partially synchronous systems, designing a leader election algorithm, that does not permit multiple leaders while the system is unstable, is a complex task. As a result many production systems use third-party distributed coordination services, such as ZooKeeper and Chubby, to provide a reliable leader election…

    Leader election protocols are a fundamental building block for replicated distributed services. They ease the design of leader-based coordination protocols that tolerate failures. In partially synchronous systems, designing a leader election algorithm, that does not permit multiple leaders while the system is unstable, is a complex task. As a result many production systems use third-party distributed coordination services, such as ZooKeeper and Chubby, to provide a reliable leader election service. However, adding a third-party service such as ZooKeeper to a distributed system incurs additional operational costs and complexity. ZooKeeper instances must be kept running on at least three machines to ensure its high availability. In this paper, we present a novel leader election protocol using NewSQL databases for partially synchronous systems, that ensures at most one leader at any given time. The leader election protocol uses the database as distributed shared memory. Our work enables distributed systems that already use NewSQL databases to save the operational overhead of managing an additional third-party service for leader election. Our main contribution is the design, implementation and validation of a practical leader election algorithm, based on NewSQL databases, that has performance comparable to a leader election implementation using a state-of-the-art distributed coordination service, ZooKeeper.

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  • FastCast: A Throughput- and Latency-Efficient Total Order Broadcast Protocol

    Middleware 2013

    Many uniform total order broadcast protocols have been designed in the last 30 years. Unfortunately, none of them achieves both optimal throughput and low latency. Indeed, protocols achieving optimal throughput rely on a ring dissemination pattern, which induces high latencies. Protocols achieving low latency rely on IP multicast and fail to achieve good throughput because of message losses. In this paper, we describe FastCast, the first protocol that achieves both optimal throughput and low…

    Many uniform total order broadcast protocols have been designed in the last 30 years. Unfortunately, none of them achieves both optimal throughput and low latency. Indeed, protocols achieving optimal throughput rely on a ring dissemination pattern, which induces high latencies. Protocols achieving low latency rely on IP multicast and fail to achieve good throughput because of message losses. In this paper, we describe FastCast, the first protocol that achieves both optimal throughput and low latency. To achieve low latency, FastCast relies on IP multicast. To achieve optimal throughput, FastCast defines a protocol responsible for dynamically computing the throughput at which processes can send IP multicast messages. Thanks to this dynamic bandwidth allocation protocol, FastCast allows multiple processes to simultaneously send messages, while avoiding message losses. An evaluation of FastCast on a cluster of 8 machines shows that it indeed achieves optimal throughput and a very low latency.

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  • RAC : a Freerider-resilient, Scalable, Anonymous Communication Protocol

    ICDCS 2013

    Enabling anonymous communication over the Internet is crucial. The first protocols that have been devised for anonymous communication are subject to freeriding. Recent protocols have thus been proposed to deal with this issue. However, these protocols do not scale to large systems, and some of them further assume the existence of trusted servers. In this paper, we present RAC, the first anonymous communication protocol that tolerates freeriders and that scales to large systems. Scalability…

    Enabling anonymous communication over the Internet is crucial. The first protocols that have been devised for anonymous communication are subject to freeriding. Recent protocols have thus been proposed to deal with this issue. However, these protocols do not scale to large systems, and some of them further assume the existence of trusted servers. In this paper, we present RAC, the first anonymous communication protocol that tolerates freeriders and that scales to large systems. Scalability comes from the fact that the complexity of RAC in terms of the number of message exchanges is independent from the number of nodes in the system. Another important aspect of RAC is that it does not rely on any trusted third party. We theoretically prove, using game theory, that our protocol is a Nash equilibrium, i.e, that freeriders have no interest in deviating from the protocol. Further, we experimentally evaluate RAC using simulations. Our evaluation shows that, whatever the size of the system (up to 100.000 nodes), the nodes participating in the system observe the same throughput.

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  • P2P VoD using the self-organizing gradient overlay network

    Proceedings of the second international workshop on Self-organizing architectures

    Peer-to-peer (P2P) video-on-demand (VoD) requires that nodes collaborate in the downloading of video files as a number of file pieces. In general for VoD, a node is only interested in another node's video file pieces if its download position in the video file precedes the download position of the other node. In this paper, we capture this neighbour relation using the Gradient overlay network, a gossip-generated P2P topology. The Gradient network topology self-organizes into logical concentric…

    Peer-to-peer (P2P) video-on-demand (VoD) requires that nodes collaborate in the downloading of video files as a number of file pieces. In general for VoD, a node is only interested in another node's video file pieces if its download position in the video file precedes the download position of the other node. In this paper, we capture this neighbour relation using the Gradient overlay network, a gossip-generated P2P topology. The Gradient network topology self-organizes into logical concentric rings, such that nodes at earlier download positions in the file are found at increasing distances from the centre, while nodes that have downloaded the whole file are located in the centre of the topology. We build a P2PVoD protocol that uses nodes sampled from the Gradient overlay, and we evaluate its performance in simulation. We also present the layered gossiping architecture and discuss the role of self-organizing mechanisms in the Gradient overlay network's architecture, including positive and negative feedback, decay, and external events from the environment.

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Språk

  • French

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  • English

    Professionell yrkeskunskap

  • Swedish

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