An environment for prototyping distributed applications

Designing a distributed application is an extremely complex task. Proper facilities for prototyping distributed applications can be useful in evaluating a design, and also in understanding the effect of different parameters on the performance of an application. We describe a language for prototyping distributed applications, that supports different communication primitives with specified delay, and provides primitives to aid debugging and evaluation. Our environment for executing distributed programs supports heterogeneous computation in which processes can execute on different hardware. Different source languages can be used for coding different modules of the processes. The system has a centralized control and monitoring facility which is based on the Suntools window system.     

Distributed Data Mining in Peer-to-Peer Networks

Peer-to-peer (P2P) networks are gaining popularity in many applications such as file sharing, e-commerce, and social networking, many of which deal with rich, distributed data sources that can benefit from data mining. P2P networks are, in fact,well-suited to distributed data mining (DDM), which deals with the problem of data analysis in environments with distributed data,computing nodes,and users. This article offers an overview of DDM applications and algorithms for P2P environments,focusing particularly on local algorithms that perform data analysis by using computing primitives with limited communication overhead. The authors describe both exact and approximate local P2P data mining algorithms that work in a decentralized and communication-efficient manner.     

Synchronization Algebras with Mobility for Graph Transformations

We propose a generalization of synchronization algebras that allows to deal with mobility and local resource handling. We show how it can be used to model communication primitives for distributed and mobile computations, such as the ones used in the global computing area. We propose a graph transformation formalism in the Synchronized Hyperedge Replacement approach which is parametric w.r.t. the synchronization algebra and thus allows to model complex systems based on the chosen communication primitives. We thus unify different models described in the literature and we allow to easily define new ones. We present various examples and a case study on Fusion Calculus, showing how different semantics for it can be derived using different synchronization algebras.     

Vartalaap: A distributed multicast communication system

With the increasing proliferation of computer networks and distributed systems, there is a growing number of applications using multicast communication. This paper presents the Vartalaap system developed at IIT, Bombay. Vartalaap is an hierarchical distributed system for multicast communication over a network, implemented in a hardware-independent fashion. The multicast is achieved without resorting to unnecessary broadcasting of messages over the network. Issues covered in this paper include the primitives for multicast, the multicast model and the system architecture. We discuss the implementation of Vartalaap and compare it with some other systems. We conclude with a discussion on the limitations of the current implementation and directions for future work.     

Flexibility and coordination in event-based,loosely coupled,distributed systems

The scale and diversity of interactions in current wide-area distributed programming environments, specially in Internet-based applications, point to the fact that there is no single solution for coordinating distributed applications. Instead, what is needed is the ability to easily build and combine different coordination abstractions. In this paper, we discuss the role of some language features, such as first-class function values, closures, and coroutines, in allowing different coordination mechanisms to be constructed out of a small set of communication primitives, and to be easily mixed and combined. Using the Lua programming language, we define a basic asynchronous primitive, which allows programming in a direct event-driven style with the syntax of function calls, and, based on this primitive, we build different well-known coordination abstractions for distributed computing.     

Open Heterogeneous Computing in Actorspace

A number of efforts in heterogeneous computing involve the development of basic architecture independent communication primitives. We present a new programming paradigm, called ActorSpace, which provides a new communication model based on destination patterns. An actorspace is a computationally passive container of actors which acts as a context for matching patterns. Patterns are matched against listed attributes of actors and actorspaces that are visible in the actorspace. Both visibility and attributes are dynamic. Messages may be sent to one or all members of a group defined by a pattern. The paradigm provides powerful support for component-based construction of heterogeneous scalable distributed applications. In particular, it supports open interfaces to servers and pattern-directed access to software repositories.     

MOVIE model for open-systems-based high-performance distributed computing

MOVIE (Multitasking Object-oriented Visual Interactive Environment) is a new software system for high-performance distributed computing (HPDC), currently in the advanced design and implementation stage at Northeast Parallel Architectures Center (NPAC), Syracuse University. The MOVIE system is structured as a multiserver network of interpreters of the high-level object-oriented programming language MovieScript. MovieScript derives from PostScript and extends it in the C⁺⁺ syntax-based object-oriented interpreted style towards 3D graphics, high-performance computing and general-purpose high-level communication protocol for distributed and MIMD-parallel computing. The paper describes the overall open systems-based MOVIE design and itemizes currently implemented, developed and planned components of the system.     

The SATIN Component System-A Metamodel for Engineering Adaptable Mobile Systems

Mobile computing devices, such as personal digital assistants and mobile phones, are becoming increasingly popular, smaller, and more capable. We argue that mobile systems should be able to adapt to changing requirements and execution environments. Adaptation requires the ability-to reconfigure the deployed code base on a mobile device. Such reconfiguration is considerably simplified if mobile applications are component-oriented rather than monolithic blocks of code. We present the SATIN (system adaptation targeting integrated networks) component metamodel, a lightweight local component metamodel that offers the flexible use of logical mobility primitives to reconfigure the software system by dynamically transferring code. The metamodel is implemented in the SATIN middleware system, a component-based mobile computing middleware that uses the mobility primitives defined in the metamodel to reconfigure both itself and applications that it hosts. We demonstrate the suitability of SATIN in terms of lightweightedness, flexibility, and reusability for the creation of adaptable mobile systems by using it to implement, port, and evaluate a number of existing and new applications, including an active network platform developed for satellite communication at the European space agency. These applications exhibit different aspects of adaptation and demonstrate the flexibility of the approach and the advantages gained     

Using optimistic atomic broadcast in transaction processing systems

Atomic broadcast primitives are often proposed as a mechanism to allow fault-tolerant cooperation between sites in a distributed system. Unfortunately, the delay incurred before a message can be delivered makes it difficult to implement high performance, scalable applications on top of atomic broadcast primitives. Recently, a new approach has been proposed for atomic broadcast which, based on optimistic assumptions about the communication system, reduces the average delay for message delivery to the application. We develop this idea further and show how applications can take even more advantage of the optimistic assumption by overlapping the coordination phase of the atomic broadcast algorithm with the processing of delivered messages. In particular, we present a replicated database architecture that employs the new atomic broadcast primitive in such a way that communication and transaction processing are fully overlapped, providing high performance without relaxing transaction correctness.     

Communication and Synchronization Primitives for Distributed Programs

A distributed program is a collection of several processes which execute concurrently, possibly in different nodes of a distributed system, and which cooperate with each other to realize a common goal. In this paper, we present a design of communication and synchronization primitives for distributed programs. The primitives are designed such that they can be provided by a kernel of a distributed operating system. An important feature of the design is that the configuration of a process, i.e., identities of processes with which the process communicates, is specified separately from the computation performed by the process. This permits easy configuration and reconfiguration of processes. We identify different kinds of communication failures, and provide distinct mechanisms for handling them. The communication primitives are not atomic actions. To enable the construction of atomic actions, two new program components, atomic agent and manager are introduced. These are devoid of policy decisions regarding concurrency control and atomic commitment. We introduce the notion of conflicts relation using which a designer can construct either an optimistic or a pessimistic concurrency control scheme. The design also incorporates primitives for constructing nested atomic actions.     

Communication Optimizations for Irregular Scientific Computations on Distributed Memory Architectures

This paper describes a number of optimizations that can be used to support the efficient execution of irregular problems on distributed memory parallel machines. These primitives (1) coordinate interprocessor data movement, (2) manage the storage of, and access to, copies of off-processor data, (3) minimize interprocessor communication requirements, and (4) support a shared name space. We present a detailed performance and scalability analysis of the communication primitives. This performance and scalability analysis is carried out using a workload generator, kernels from real applications, and a large unstructured adaptive application (the molecular dynamics code CHARMM).     

In-kernel integration of operating system and infiniband functions for high performance computing clusters: a DSM example

The infiniband (IB) system area network (SAN) enables applications to access hardware directly from user level, reducing the overhead of user-kernel crossings during data transfer. However, distributed applications that exhibit close coupling between network and OS services may benefit from accessing IB from the kernel through IB's native verbs interface, which permits tight integration of these services. We assess this approach using a sequential-consistency distributed shared memory (DSM) system as an example. We first develop primitives that abstract the low-level communication and kernel details, and efficiently serve the application's communication, memory, and scheduling needs. Next, we combine the primitives to form a kernel DSM protocol. The approach is evaluated using our full-fledged Linux kernel DSM implementation over infiniband. We show that overheads are reduced substantially, and overall application performance is improved in terms of both absolute execution time and scalability relative to an entirely user level implementation.     

Cost-effective designs of WDM optical interconnects

Optical communication, in particular, wavelength-division-multiplexing (WDM) technique, has become a promising networking choice to meet ever-increasing demands on bandwidth from emerging bandwidth-intensive computing/communication applications, such as data browsing in the World Wide Web, multimedia conferencing, e-commerce, and video-on-demand services. As optics becomes a major networking media in all communications needs, optical interconnects will inevitably play an important role in interconnecting processors in parallel and distributed computing systems. We consider a cost-effective design of WDM optical interconnects for current and future generation parallel and distributed computing and communication systems. We first categorize WDM optical interconnects into two different connection models based on their target applications: the wavelength-based model and the fiber-link-based model. Most of existing WDM optical interconnects belong to the first category. We then present a minimum cost design for WDM optical interconnects under wavelength-based model by using sparse crossbar switches instead of full crossbar switches in combination with wavelength converters. For applications that use the fiber-link-based model, we show that network cost can be significantly reduced, and present such a minimum cost design for WDM optical interconnects under this model. Finally, we generalize the idea used in the design for the fiber-link-based model to WDM optical interconnects under the wavelength-based model, and obtain another new design that can trade off switch cost with wavelength converter cost in this type of WDM optical interconnect. The results in this paper are applicable to any emerging optical switching technologies, such as SOA-based and MEMS-based technologies.     

Partitioned encryption and achieving simultaneity by partitioning

We present a method called Partitioned Encryption whose main property is its simplicity. It is an extension of Probabilistic Public-Key Encryption, which can be used in designing cryptographic protocols and can be applied to distributed problem solving. We also give a modification of Secret Sharing called Partitioned Secret Sharing. We demonstrate the power of Partitioned Encryption: combining it with the partitioning of the user set gives a solution scheme for ‘Verifiable Secret Sharing’ and ‘Simultaneous Broadcast in the Presence of Faults’, which are important primitives of fault-tolerant distributed computing introduced by Chor, Goldwasser, Micali and Awerbuch (1985). The scheme is fully polynomial, simple, and efficient in terms of communication rounds. The basic partitioning methods are suggested as general tools for distributed computing, which are easy to implement and analyze.     

CARISMA: context-aware reflective middleware system for mobile applications

Mobile devices, such as mobile phones and personal digital assistants, have gained wide-spread popularity. These devices will increasingly be networked, thus enabling the construction of distributed applications that have to adapt to changes in context, such as variations in network bandwidth, battery power, connectivity, reachability of services and hosts, etc. In this paper, we describe CARISMA, a mobile computing middleware which exploits the principle of reflection to enhance the construction of adaptive and context-aware mobile applications. The middleware provides software engineers with primitives to describe how context changes should be handled using policies. These policies may conflict. We classify the different types of conflicts that may arise in mobile computing and argue that conflicts cannot be resolved statically at the time applications are designed, but, rather, need to be resolved at execution time. We demonstrate a method by which policy conflicts can be handled; this method uses a microeconomic approach that relies on a particular type of sealed-bid auction. We describe how this method is implemented in the CARISMA middleware architecture and sketch a distributed context-aware application for mobile devices to illustrate how the method works in practice. We show, by way of a systematic performance evaluation, that conflict resolution does not imply undue overheads, before comparing our research to related work and concluding the paper.     

Supporting Cost-Effective Fault Tolerance in Distributed Message-Passing Applications with File Operations

In this paper we present an approach to reliable distributed computing, which incorporates fault tolerance into applications at low cost, in terms of both run-time performance and programming effort required to construct reliable application software. In our model fault tolerance is based on distributed consistent checkpointing and rollback-recovery integrated with a user-level reliable transmission protocol. By employing novel techniques 8and algorithms, our approach is distinguished from other consistent checkpointing schemes by the following features: first, minimum communication overhead for constructing a consistent distributed checkpoint and catching messages in transit during checkpointing; second, tolerance to message losses due to site failures or unreliable non-FIFO networks; and third, efficient checkpointing and recovery of persistent state, i.e., user files. Based on the model, a software library prototype called Libra has been implemented for supporting fault tolerance in distributed message-passing applications with file operations. The library provides an easy to use programming interface including message-passing and file I/O primitives, which hides the complexity of both fault-tolerant network communications and checkpointing and recovering user files from the application level. Experience with a number of long-running distributed applications shows that Libra can provide fault tolerance in a cost-effective manner.     

分布式计算机及其应用发展浅析

随着信息技术不断进步的脚步,信息交流的频繁程度和多样化交流方式也日益增强。分布式计算在计算机网络的出现之后成为可能,本文通过对分布式计算机的介绍和现阶段的应用情况概述来预测未来分布式计算的应用发展方向。     

Live Distributed Objects: Enabling the Active Web

Distributed computing has lagged behind the productivity revolution that has transformed the desktop in recent years. Programmers still generally treat the Web as a separate technology space and develop network applications using low-level message-passing primitives or unreliable Web services method invocations. Live distributed objects are designed to offer developers a scalable multicast infrastructure that's tightly integrated with a runtime environment.     

Transactions involving multicast

Multicast is concurrent data transmission to a well-defined and restricted set of destinations. Although this would seem to be a useful facility for many applications in distributed computing, very little use is made of it in practice. This is in spite of the fact that several multicast protocols exist which offer one or more multicast primitives to the applications programmer^1–5. This paper investigates the reasons for their limited acceptance, discussing the difficulties involved in using multicast, and where applicable, gives a review of approaches and solutions to be found in the literature.     

An analysis of VI Architecture primitives in support of parallel and distributed communication

We present the results of a detailed study of the Virtual Interface (VI) paradigm as a communication foundation for a distributed computing environment. Using Active Messages and the Split‐C global memory model, we analyze the inherent costs of using VI primitives to implement these high‐level communication abstractions. We demonstrate a minimum mapping cost (i.e. the host processing required to map one abstraction to a lower abstraction) of 5.4 μs for both Active Messages and Split‐C using four‐way 550 MHz Pentium III SMPs and the Myrinet network. We break down this cost to the use of individual VI primitives in supporting flow control, buffer management and event processing and identify the completion queue as the source of the highest overhead. Bulk transfer performance plateaus at 44 Mbytes/s for both implementations are due to the addition of fragmentation requirements. Based on this analysis, we present the implications for the VI successor, Infiniband. Copyright © 2002 John Wiley & Sons, Ltd.