In a system containing several distributed servers, messages of random sizes generated at different locations must be disseminated and processed in the same order by all hosts. A ring protocol is defined, where a number of folders carrying messages circulate in one direction without overtaking each other. A model involving parallel queues is analysed in the steady state and is solved approximately, allowing the computation of performance measures. A number of example systems are evaluated numerically and by simulations, leading to a heuristic for choosing the optimal number of folders.

Mammoth transactions, which involve long-running operations that access many items, are common in graph workloads. Graph analytics tasks, including pattern matching and graph algorithms, can generate large read-write operations that impact significant portions of data, which makes their execution challenging under strict isolation guarantees. Consequently, we face an apparent trade-off between ensuring high isolation and achieving high performance, forcing users to choose between the two. In this work, we present TuskFlow, an experimental graph database based on Neo4j, designed to efficiently handle mammoth transactions on graphs (the technique is applicable to other models such as relational) while maintaining existing transactional semantics. TuskFlow employs a deterministic protocol that safely reorders regular transactions around mammoths within an epoch. Our protocol supports parallel mammoth execution inspired by graph-parallel algorithms. To minimize conflicts with regular transactions, TuskFlow introduces query- and workload-aware optimizations, including graph entity tagging and partitioning. Our experiments demonstrate that, unlike traditional protocols like two-phase locking or MVCC, TuskFlow avoids blocking write transactions and improves tail latency by up to 45×.

BIFROST is a novel query engine for graph databases that supports high-fidelity data modeling on arbitrary and evolving graph topologies. It dynamically optimizes queries according to meta-level changes in the underlying graph (i.e. changes in topology) without the need for any explicit schema. This is possible by using state-of-the-art techniques from managed programming languages, such as self-optimizing ASTs and deoptimization, to combine query optimization and compilation. The approach provides high fidelity for even highly irregular labeled property graphs and gives good performance when compared to other systems that depend on fixed schemas for query planning and optimization.

Distributed OLTP systems execute the high-overhead, two-phase commit (2PC) protocol at the end of every distributed transaction. Epoch-based commit proposes that 2PC be executed only once for all transactions processed within a time interval called an epoch. Increasing epoch duration allows more transactions to be processed before the common 2PC. It thus reduces 2PC overhead per transaction, increases throughput but also increases average transaction latency. Therefore, required is the ability to choose the right epoch size that offers the desired trade-off between throughput and latency. To this end, we develop two analytical models to estimate throughput and average latency in terms of epoch size taking into account load and failure conditions. Simulations affirm their accuracy and effectiveness. We then present epoch-based multi-commit which, unlike epoch-based commit, seeks to avoid all transactions being aborted when failures occur, and also performs identically when failures do not occur. Our performance study identifies workload factors that make it more effective in preventing transaction aborts and concludes that the analytical models can be equally useful in predicting its performance as well.

Despite their proliferation as a dominant computing paradigm, cloud computing systems lack effective mechanisms to manage their vast amounts of resources efficiently. Resources are stranded and fragmented, ultimately limiting cloud systems' applicability to large classes of critical applications that pose non-moderate resource demands. Eliminating current technological barriers of actual fluidity and scalability of cloud resources is essential to strengthen cloud computing's role as a critical cornerstone for the digital economy. ACTiCLOUD proposes a novel cloud architecture that breaks the existing scale-up and share-nothing barriers and enables the holistic management of physical resources both at the local cloud site and at distributed levels. Specifically, it makes advancements in the cloud resource management stacks by extending state-of-the-art hypervisor technology beyond the physical server boundary and localized cloud management system to provide a holistic resource management within a rack, within a site, and across distributed cloud sites. On top of this, ACTiCLOUD will adapt and optimize system libraries and runtimes (e.g., JVM) as well as ACTiCLOUD-native applications, which are extremely demanding, and critical classes of applications that currently face severe difficulties in matching their resource requirements to state-of-the-art cloud offerings.

The Web services and service-oriented architectures (SOA) vision by Helland, P. (2005) is about building large-scale distributed applications by composing coarse-grained autonomous services in a flexible architecture that can adapt to changing business requirements. These services interact by exchanging one-way messages through standardized message processing and transport protocols. This vision is being driven by economic imperatives for integration and automation across administrative and organizational boundaries. This paper presents a concise yet expressive model for service contracts to describe messaging behavior. The idea is simple: we use Boolean conditions to specify when a message can be sent and received, where the conditions refer only to other messages in the service contract - that is, conditions only refer to a service's externalized messaging state and not to internal state

Abstract The U.K. e‐Science Programme is a £250 million, five‐year initiative which has funded over 100 projects. These application‐led projects are underpinned by an emerging set of core middleware services that allow the coordinated, collaborative use of distributed resources. This set of middleware services runs on top of the research network and beneath the applications we call the ‘Grid’. Grid middleware is currently in transition from pre‐Web Service versions to a new version based on Web Services. Unfortunately, only a very basic set of Web Services embodied in the Web Services Interoperability proposal, WS‐I, are agreed by most IT companies. IBM and others have submitted proposals for Web Services for Grids—the Web Services ResourceFramework and Web Services Notification specifications—to the OASIS organization for standardization. This process could take up to 12 months from March 2004 and the specifications are subject to debate and potentially significant changes. Since several significant U.K. e‐Science projects come to an end before the end of this process, the U.K. needs to develop a strategy that will protect the U.K.'s investment in Grid middleware by informing the Open Middleware Infrastructure Institute's (OMII) roadmap and U.K. middleware repository in Southampton. This paper sets out an evolutionary roadmap that will allow us to capture generic middleware components from projects in a form that will facilitate migration or interoperability with the emerging Grid Web Services standards and with ongoing OGSA developments. In this paper we therefore define a set of Web Services specifications, which we call ‘WS‐I+’ to reflect the fact that this is a larger set than currently accepted by WS‐I, that we believe will enable us to achieve the twin goals of capturing these components and facilitating migration to future standards. We believe that the extra Web Services specifications we have included in WS‐I+ are both helpful in building e‐Science Grids and likely to be widely accepted. Copyright © 2005 John Wiley & Sons, Ltd.

Abstract This paper presents the motivation and design decisions for the Web Services Grid Application Framework (WS‐GAF), which is a mapping of Grid architecture requirements onto the Web Services Architecture. The goal for WS‐GAF is to describe a framework for building Grid applications that adheres to the principles of service‐oriented architectures and utilizes existing Web Services technologies. The proposed solution addresses issues including stateful interactions, logical resource naming, metadata, and lifetime management. Copyright © 2005 John Wiley & Sons, Ltd.