32,071 research outputs found
Creating a Distributed Programming System Using the DSS: A Case Study of OzDSS
This technical report describes the integration of the Distribution Subsystem (DSS) to the programming system Mozart. The result, OzDSS, is described in detail. Essential when coupling a programming system to the DSS is how the internal model of threads and language entities are mapped to the abstract entities of the DSS. The model of threads and language entities of Mozart is described at a detailed level to explain the design choices made when developing the code that couples the DSS to Mozart. To show the challenges associated with different thread implementations, the C++DSS system is introduced. C++DSS is a C++ library which uses the DSS to implement different types of distributed language entities in the form of C++ classes. Mozart emulates threads, thus there is no risk of multiple threads accessing the DSS simultaneously. C++DSS, on the other hand, makes use of POSIX threads, thus simultaneous access to the DSS from multiple POSIX threads can happen. The fundamental differences in how threads are treated in a system that emulates threads (Mozart) to a system that make use of native-threads~(C++DSS) is discussed. The paper is concluded by a performance comparison between the OzDSS system and other distributed programming systems. We see that the OzDSS system outperforms ``industry grade'' Java-RMI and Java-CORBA implementations
FRIENDS - A flexible architecture for implementing fault tolerant and secure distributed applications
FRIENDS is a software-based architecture for implementing fault-tolerant and, to some extent, secure applications. This architecture is composed of sub-systems and libraries of metaobjects. Transparency and separation of concerns is provided not only to the application programmer but also to the programmers implementing metaobjects for fault tolerance, secure communication and distribution. Common services required for implementing metaobjects are provided by the sub-systems. Metaobjects are implemented using object-oriented techniques and can be reused and customised according to the application needs, the operational environment and its related fault assumptions. Flexibility is increased by a recursive use of metaobjects. Examples and experiments are also described
A metaobject architecture for fault-tolerant distributed systems : the FRIENDS approach
The FRIENDS system developed at LAAS-CNRS is a metalevel architecture providing libraries of metaobjects for fault
tolerance, secure communication, and group-based distributed applications. The use of metaobjects provides a nice separation of concerns between mechanisms and applications. Metaobjects can be used transparently by applications and can be composed according to the needs of a given application, a given architecture, and its underlying properties. In FRIENDS, metaobjects are used recursively to add new properties to applications. They are designed using an object oriented design method and implemented on top of basic system services. This paper describes the FRIENDS software-based architecture, the object-oriented development of metaobjects, the experiments that we have done, and summarizes the advantages and drawbacks of a metaobject approach for building fault-tolerant system
System Support for Managing Invalid Bindings
Context-aware adaptation is a central aspect of pervasive computing
applications, enabling them to adapt and perform tasks based on contextual
information. One of the aspects of context-aware adaptation is reconfiguration
in which bindings are created between application component and remote services
in order to realize new behaviour in response to contextual information.
Various research efforts provide reconfiguration support and allow the
development of adaptive context-aware applications from high-level
specifications, but don't consider failure conditions that might arise during
execution of such applications, making bindings between application and remote
services invalid. To this end, we propose and implement our design approach to
reconfiguration to manage invalid bindings. The development and modification of
adaptive context-aware applications is a complex task, and an issue of an
invalidity of bindings further complicates development efforts. To reduce the
development efforts, our approach provides an application-transparent solution
where the issue of the invalidity of bindings is handled by our system,
Policy-Based Contextual Reconfiguration and Adaptation (PCRA), not by an
application developer. In this paper, we present and describe our approach to
managing invalid bindings and compare it with other approaches to this problem.
We also provide performance evaluation of our approach
Implementing fault tolerant applications using reflective object-oriented programming
Abstract: Shows how reflection and object-oriented programming can be used to ease the implementation of classical fault tolerance mechanisms in distributed applications. When the underlying runtime system does not provide fault tolerance transparently, classical approaches to implementing fault tolerance mechanisms often imply mixing functional programming with non-functional programming (e.g. error processing mechanisms). The use of reflection improves the transparency of fault tolerance mechanisms to the programmer and more generally provides a clearer separation between functional and non-functional programming. The implementations of some classical replication techniques using a reflective approach are presented in detail and illustrated by several examples, which have been prototyped on a network of Unix workstations. Lessons learnt from our experiments are drawn and future work is discussed
A Configurable Transport Layer for CAF
The message-driven nature of actors lays a foundation for developing scalable
and distributed software. While the actor itself has been thoroughly modeled,
the message passing layer lacks a common definition. Properties and guarantees
of message exchange often shift with implementations and contexts. This adds
complexity to the development process, limits portability, and removes
transparency from distributed actor systems.
In this work, we examine actor communication, focusing on the implementation
and runtime costs of reliable and ordered delivery. Both guarantees are often
based on TCP for remote messaging, which mixes network transport with the
semantics of messaging. However, the choice of transport may follow different
constraints and is often governed by deployment. As a first step towards
re-architecting actor-to-actor communication, we decouple the messaging
guarantees from the transport protocol. We validate our approach by redesigning
the network stack of the C++ Actor Framework (CAF) so that it allows to combine
an arbitrary transport protocol with additional functions for remote messaging.
An evaluation quantifies the cost of composability and the impact of individual
layers on the entire stack
Internal Design of the DSS
This technical report describes the implementation of the DSS middleware with focus on the design of the abstract entity interface and the coordination layer. Key concepts are highlighted and described, on the level of C++ classes
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