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1. Instability in Geo-Distributed Kubernetes Federation: Causes and Mitigation

Author

Guillaume Pierre, Mulugeta Ayalew Tamiru, Erik Elmroth, Johan Tordsson, Elastisys AB, Design and Implementation of Autonomous Distributed Systems (MYRIADS), Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-SYSTÈMES LARGE ÉCHELLE (IRISA-D1), Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), This work is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 765452. The information and views set out in this publication are those of the author(s) and do not necessarilyreflect the official opinion of the European Union. Neither the European Union institutions and bodies nor any person acting on their behalf maybe held responsible for the use which may be made of the information contained therein. Experiments presented in this paper were carried out using the Grid’5000 testbed, supported by a scientific interest group hosted by Inria and including CNRS, RENATER and several Universities as well as other organizations (see https://www.grid5000.fr), European Project: 765452,h2020,H2020-MSCA-ITN-2017,FogGuru(2017), Université de Bretagne Sud (UBS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National de Recherche en Informatique et en Automatique (Inria)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-CentraleSupélec-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université de Bretagne Sud (UBS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1)

Subjects
Computer science, Distributed computing, System stability, 020207 software engineering, Automatic configuration tuning, 02 engineering and technology, Fog Computing, Network connectivity, Instability, Self adaptation, Self-configuration, Fog computing, 020204 information systems, Kubernetes Federation, 0202 electrical engineering, electronic engineering, information engineering, Feedback controller, [INFO.INFO-OS]Computer Science [cs]/Operating Systems [cs.OS], Latency (engineering), Self-adaptation, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

International audience; As resources in geo-distributed environments are typically located in remote sites characterized by high latency and intermittent network connectivity, delays and transient network failures are common between the management layer and the remote resources. In this paper, we show that delays and transient network failures coupled with static configuration, including the default configuration parameter values, can lead to instability of application deployments in Kubernetes Federation, making applications unavailable for long periods of time. Leveraging on the benefits of configuration tuning, we propose a feedback controller to dynamically adjust the concerned configuration parameter to improve the stability of application deployments without slowing down the detection of hard failures. We show the effectiveness of our approach in a geo-distributed setup across five sites of Grid'5000, bringing system stability from 83-92% with no controller to 99.5-100% using the controller.

Published
2020

2. Vortex cycles at the inner edges of dead zones in protoplanetary disks

Author

S. Fromang, Heloise Meheut, Julien Faure, Henrik N. Latter, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Department of Applied Mathematics and Theoretical Physics (DAMTP), University of Cambridge [UK] (CAM), J.F., S.F., and H.M. acknowledge funding from the European Research Council underthe European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement No. 258729. HL acknowledges support via STFC grant ST/G/002584/1. The simulations presented in this paper were granted access to the HPC resources of Cines under the allocation x2013042231 and x2014042231 made by GENCI (Grand Equipement National de Calcul Intensif)., European Project: 258729,EC:FP7:ERC,ERC-2010-StG_20091028,PETADISK(2011), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), and Department of Applied Mathematics and Theoretical Physics / Centre for Mathematical Sciences (DAMTP/CMS)

Subjects
010504 meteorology & atmospheric sciences, FOS: Physical sciences, Context (language use), Astrophysics, Protoplanetary disk, 01 natural sciences, Instability, Physics::Fluid Dynamics, 0103 physical sciences, planets and satellites: formation, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Computer simulation, Turbulence, protoplanetary disks, Rossby wave, Astronomy and Astrophysics, Laminar flow, Mechanics, Vortex, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Earth and Planetary Astrophysics
Abstract

In protoplanetary disks, the inner boundary between the turbulent and laminar regions is a promising site for planet formation because solids may become trapped at the interface itself or in vortices generated by the Rossby wave instability. The disk thermodynamics and the turbulent dynamics at that location are entwined because of the importance of turbulent dissipation on thermal ionization and, conversely, of thermal ionisation on the turbulence. However, most previous work has neglected this dynamical coupling and have thus missed a key element of the physics in this region. In this paper, we aim to determine how the the interplay between ionization and turbulence impacts on the formation and evolution of vortices at the interface between the active and the dead zones. Using the Godunov code RAMSES, we have performed a 3D magnetohydrodynamic global numerical simulation of a cylindrical model of an MRI--turbulent protoplanetary disk, including thermodynamical effects as well as a temperature-dependant resistivity. The comparison with an analogous 2D viscous simulation has been extensively used to help identify the relevant physical processes and the disk's long-term evolution. We find that a vortex formed at the interface, due to Rossby wave instability, migrates inward and penetrates the active zone where it is destroyed by turbulent motions. Subsequently, a new vortex emerges a few tens of orbits later at the interface, and the new vortex migrates inward too. The sequence repeats itself, resulting in cycles of vortex formation, migration, and disruption. This behavior is successfully reproduced using two different codes. In this paper, we characterize this vortex life cycle and discuss its implications for planet formation at the dead/active interface. Our simulations highlight the importance of thermodynamical processes for the vortex evolution at the dead zone inner edge., Comment: 13 pages, 15 figures

Published
2015