417,614 research outputs found
DYNAMIC CONFIGURATION FOR DISTRIBUTED SYSTEMS
Published versio
Tight Bounds for Asymptotic and Approximate Consensus
We study the performance of asymptotic and approximate consensus algorithms
under harsh environmental conditions. The asymptotic consensus problem requires
a set of agents to repeatedly set their outputs such that the outputs converge
to a common value within the convex hull of initial values. This problem, and
the related approximate consensus problem, are fundamental building blocks in
distributed systems where exact consensus among agents is not required or
possible, e.g., man-made distributed control systems, and have applications in
the analysis of natural distributed systems, such as flocking and opinion
dynamics. We prove tight lower bounds on the contraction rates of asymptotic
consensus algorithms in dynamic networks, from which we deduce bounds on the
time complexity of approximate consensus algorithms. In particular, the
obtained bounds show optimality of asymptotic and approximate consensus
algorithms presented in [Charron-Bost et al., ICALP'16] for certain dynamic
networks, including the weakest dynamic network model in which asymptotic and
approximate consensus are solvable. As a corollary we also obtain
asymptotically tight bounds for asymptotic consensus in the classical
asynchronous model with crashes.
Central to our lower bound proofs is an extended notion of valency, the set
of reachable limits of an asymptotic consensus algorithm starting from a given
configuration. We further relate topological properties of valencies to the
solvability of exact consensus, shedding some light on the relation of these
three fundamental problems in dynamic networks
Collaborative Computation in Self-Organizing Particle Systems
Many forms of programmable matter have been proposed for various tasks. We
use an abstract model of self-organizing particle systems for programmable
matter which could be used for a variety of applications, including smart paint
and coating materials for engineering or programmable cells for medical uses.
Previous research using this model has focused on shape formation and other
spatial configuration problems (e.g., coating and compression). In this work we
study foundational computational tasks that exceed the capabilities of the
individual constant size memory of a particle, such as implementing a counter
and matrix-vector multiplication. These tasks represent new ways to use these
self-organizing systems, which, in conjunction with previous shape and
configuration work, make the systems useful for a wider variety of tasks. They
can also leverage the distributed and dynamic nature of the self-organizing
system to be more efficient and adaptable than on traditional linear computing
hardware. Finally, we demonstrate applications of similar types of computations
with self-organizing systems to image processing, with implementations of image
color transformation and edge detection algorithms
Dynamic Firewall Configuration Using Mobile Agents
The nearly omnipresence ofthe Internet and the steady increase ofwireless computing
and mobile devices require highly dynamic adaptable distributed system architectures.
Building such architectures needs a combination ofkey concepts from component
technology and distributed systems. Mobile agents provide this combination. We use
mobile agents as the building blocks ofacomponent-based system for remote supervision
and control of both hard- and software in a distributed environment. In this paper we
concentrate on the configuration ofindividual components and component relationships
in our system. We identify requirements for remote configuration ofagent-based
component systems and discuss architectural and user interface related issues ofour
approaches. We use acode-on-demand approach for supporting elaborate user interfaces.
We use a generative approach based on enhanced meta-information for reducing
development effort. The presented approaches are applicable for remote configuration of
component-based systems in general and consider additional requirements imposed
through the use of mobile agenttechnology
Autonomic Management in a Distributed Storage System
This thesis investigates the application of autonomic management to a
distributed storage system. Effects on performance and resource consumption
were measured in experiments, which were carried out in a local area test-bed.
The experiments were conducted with components of one specific distributed
storage system, but seek to be applicable to a wide range of such systems, in
particular those exposed to varying conditions. The perceived characteristics
of distributed storage systems depend on their configuration parameters and on
various dynamic conditions. For a given set of conditions, one specific
configuration may be better than another with respect to measures such as
resource consumption and performance. Here, configuration parameter values were
set dynamically and the results compared with a static configuration. It was
hypothesised that under non-changing conditions this would allow the system to
converge on a configuration that was more suitable than any that could be set a
priori. Furthermore, the system could react to a change in conditions by
adopting a more appropriate configuration. Autonomic management was applied to
the peer-to-peer (P2P) and data retrieval components of ASA, a distributed
storage system. The effects were measured experimentally for various workload
and churn patterns. The management policies and mechanisms were implemented
using a generic autonomic management framework developed during this work. The
experimental evaluations of autonomic management show promising results, and
suggest several future research topics. The findings of this thesis could be
exploited in building other distributed storage systems that focus on
harnessing storage on user workstations, since these are particularly likely to
be exposed to varying, unpredictable conditions.Comment: PhD Thesis, University of St Andrews, 2009. Supervisor: Graham Kirb
Configuration Management for Distributed Software Services
The paper describes the SysMan approach to interactive configuration management of distributed software components (objects). Domains are used to group objects to apply policy and for convenient naming of objects. Configuration Management involves using a domain browser to locate relevant objects within the domain service; creating new objects which form a distributed service; allocating these objects to physical nodes in the system and binding the interfaces of the objects to each other and to existing services. Dynamic reconfiguration of the objects forming a service can be accomplished using this tool. Authorisation policies specify which domains are accessible by which managers and which interfaces can be bound together. Keywords Domains, object creation, object binding, object allocation, graphical management interface. 1 INTRODUCTION The object-oriented approach brings considerable benefits to the design and implementation of software for distributed systems (Kramer 1992). Con..
Modeling and Validation of the Dynamic Host Configuration Protocol with Colored Petri Nets
Petri Networks with a graphical language are based on mathematical logic which have many uses and have capability for modeling and validation of distributed systems and concurrent applications. Colored Petri Networks (CPNs) are a type of Petri Network models that are used in modeling of systems which contain discrete and scattered events. In general, CPNs are used to evaluate system performance and demonstrate the correctness of systems. Dynamic Host Configuration Protocol (DHCP) is one of the main systems of protocols special for servers that are used for dynamic allocation of IP to the network computers (clients). In this paper, we highlight to analyze the correctness and authenticity of DHCPs with the use of CPNs with using the CPN Tools and to prove the accuracy of our protocol's performance.DOI:http://dx.doi.org/10.11591/ijece.v2i3.48
Design and Analysis of a Logless Dynamic Reconfiguration Protocol
Distributed replication systems based on the replicated state machine model
have become ubiquitous as the foundation of modern database systems. To ensure
availability in the presence of faults, these systems must be able to
dynamically replace failed nodes with healthy ones via dynamic reconfiguration.
MongoDB is a document oriented database with a distributed replication
mechanism derived from the Raft protocol. In this paper, we present
MongoRaftReconfig, a novel dynamic reconfiguration protocol for the MongoDB
replication system. MongoRaftReconfig utilizes a logless approach to managing
configuration state and decouples the processing of configuration changes from
the main database operation log. The protocol's design was influenced by
engineering constraints faced when attempting to redesign an unsafe, legacy
reconfiguration mechanism that existed previously in MongoDB. We provide a
safety proof of MongoRaftReconfig, along with a formal specification in TLA+.
To our knowledge, this is the first published safety proof and formal
specification of a reconfiguration protocol for a Raft-based system. We also
present results from model checking its safety properties on finite protocol
instances. Finally, we discuss the conceptual novelties of MongoRaftReconfig,
how it can be understood as an optimized and generalized version of the single
server reconfiguration algorithm of Raft, and present an experimental
evaluation of how its optimizations can provide performance benefits for
reconfigurations.Comment: 35 pages, 2 figure
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