689 research outputs found
Hosting Byzantine Fault Tolerant Services on a Chord Ring
In this paper we demonstrate how stateful Byzantine Fault Tolerant services
may be hosted on a Chord ring. The strategy presented is fourfold: firstly a
replication scheme that dissociates the maintenance of replicated service state
from ring recovery is developed. Secondly, clients of the ring based services
are made replication aware. Thirdly, a consensus protocol is introduced that
supports the serialization of updates. Finally Byzantine fault tolerant
replication protocols are developed that ensure the integrity of service data
hosted on the ring.Comment: Submitted to DSN 2007 Workshop on Architecting Dependable System
A Framework for Constraint-Based Deployment and Autonomic Management of Distributed Applications
We propose a framework for deployment and subsequent autonomic management of
component-based distributed applications. An initial deployment goal is
specified using a declarative constraint language, expressing constraints over
aspects such as component-host mappings and component interconnection topology.
A constraint solver is used to find a configuration that satisfies the goal,
and the configuration is deployed automatically. The deployed application is
instrumented to allow subsequent autonomic management. If, during execution,
the manager detects that the original goal is no longer being met, the
satisfy/deploy process can be repeated automatically in order to generate a
revised deployment that does meet the goal.Comment: Submitted to ICAC-0
H2O: An Autonomic, Resource-Aware Distributed Database System
This paper presents the design of an autonomic, resource-aware distributed
database which enables data to be backed up and shared without complex manual
administration. The database, H2O, is designed to make use of unused resources
on workstation machines. Creating and maintaining highly-available, replicated
database systems can be difficult for untrained users, and costly for IT
departments. H2O reduces the need for manual administration by autonomically
replicating data and load-balancing across machines in an enterprise.
Provisioning hardware to run a database system can be unnecessarily costly as
most organizations already possess large quantities of idle resources in
workstation machines. H2O is designed to utilize this unused capacity by using
resource availability information to place data and plan queries over
workstation machines that are already being used for other tasks. This paper
discusses the requirements for such a system and presents the design and
implementation of H2O.Comment: Presented at SICSA PhD Conference 2010 (http://www.sicsaconf.org/
Autonomic Management of Maintenance Scheduling in Chord
This paper experimentally evaluates the effects of applying autonomic
management to the scheduling of maintenance operations in a deployed Chord
network, for various membership churn and workload patterns. Two versions of an
autonomic management policy were compared with a static configuration. The
autonomic policies varied with respect to the aggressiveness with which they
responded to peer access error rates and to wasted maintenance operations. In
most experiments, significant improvements due to autonomic management were
observed in the performance of routing operations and the quantity of data
transmitted between network members. Of the autonomic policies, the more
aggressive version gave slightly better results
Applying constraint solving to the management of distributed applications
Submitted to DOA08We present our approach for deploying and managing distributed component-based applications. A Desired State Description (DSD), written in a high-level declarative language, specifies requirements for a distributed application. Our infrastructure accepts a DSD as input, and from it automatically configures and deploys the distributed application. Subsequent violations of the original requirements are detected and, where possible, automatically rectified by reconfiguration and redeployment of the necessary application components. A constraint solving tool is used to plan deployments that meet the application requirements.Postprin
A Comparative Case Study to Determine the Correlation That Exists Between the Irish PPP and the UK PFI Policies
This research attempts to examine the previous pathway and current state of play in relation to the Irish PPP policy. Commentators have identified that the origins and progression of the Irish PPP programme can be traced back to the UK PFI (PPP) policy. The focus of this study is to examine the relationship, notably âthe correlationâ that exists between both the Irish PPP and the UK PFI policies. In doing so we examine the components of both policies to try to ascertain what drove Ireland and the UK to introduce such measures, alongside the subsequent amendments that were deemed necessary. In addition, we attempt to understand what incentivises the state to engage in this form of procurement and to acknowledge the element of change that is occurring within that landscape. Our focus is centred upon the Economic, Legal, and Public Policy perspectives and how each element retains an influence over that process. In doing so we identify that the Irish authorities developed an astuteness âa niche approachâ towards the class of investment that it was willing to invest in as part of its national procurement plan; however, as the findings suggest, this was alluded to during the negotiations surrounding the NBP. In contrast, the approach taken by the Irish authorities appears to counteract the actions of the UK government who regarded the offerings of PFI as a panacea, regardless of the cost. As a consequence of which, the then UK Chancellor of the Exchequer Philip Hammond announced in October 2018, that the UK would no longer engage in PFI on the basis that the policy had become untenable. As a consequence of the UKâs departure from the EU, Ireland is now facing an uncertain future in relation to its reliance upon UK case law âlegal precedentâ; as means of addressing challenges made against its procurement decisions. From a public policy perspective, we expose the influence of the Department of Finance upon the decision-making process, alongside the homogenisation that has evolved between the EIB, the NTMA, and the NFDA. We conclude this study by reaching a determination, as to where this policy now sits as a component of the public procurement regime
A Peer-to-Peer Middleware Framework for Resilient Persistent Programming
The persistent programming systems of the 1980s offered a programming model
that integrated computation and long-term storage. In these systems, reliable
applications could be engineered without requiring the programmer to write
translation code to manage the transfer of data to and from non-volatile
storage. More importantly, it simplified the programmer's conceptual model of
an application, and avoided the many coherency problems that result from
multiple cached copies of the same information. Although technically
innovative, persistent languages were not widely adopted, perhaps due in part
to their closed-world model. Each persistent store was located on a single
host, and there were no flexible mechanisms for communication or transfer of
data between separate stores. Here we re-open the work on persistence and
combine it with modern peer-to-peer techniques in order to provide support for
orthogonal persistence in resilient and potentially long-running distributed
applications. Our vision is of an infrastructure within which an application
can be developed and distributed with minimal modification, whereupon the
application becomes resilient to certain failure modes. If a node, or the
connection to it, fails during execution of the application, the objects are
re-instantiated from distributed replicas, without their reference holders
being aware of the failure. Furthermore, we believe that this can be achieved
within a spectrum of application programmer intervention, ranging from minimal
to totally prescriptive, as desired. The same mechanisms encompass an
orthogonally persistent programming model. We outline our approach to
implementing this vision, and describe current progress.Comment: Submitted to EuroSys 200
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