Erik Klintskog

The Design and Evaluation of a Middleware Library for Distribution of Language Entities

The paper presents a modular design of a distribution middleware that supports the wide variety of entities that exist in high level languages. Such entities are classified into mutables, immutables and transients. The design is factorized in order to allow multiple consistency protocols for the same entity type, and multiple coordination strategies for implementing the protocols that differ in their failure behavior. The design is implemented and evaluated. It shows a very competitive performance.

The DSS, a middleware library for efficient and transparent distribution of language entities

This paper describes a novel language independent model for distribution of language entities, which allows for fine-grained instrumentation of entity consistency protocols on a per-entity basis. The model is implemented as a middleware component, designed to enhance arbitrary high-level programming languages with distribution support on the language entity level. The middleware library is extendable using internal interfaces to add new protocols over three different aspects of distribution.

A peer-to-peer approach to enhance middleware connectivity

One of the problems of middleware for shared state is that they are designed, explicitly or implicitly, for symmetric networks. However, since the Internet is not symmetric, end-to-end process connectivity cannot be guaranteed. Our solution to this is to provide the middleware with a network abstraction layer that masks the asymmetry of the network and provides the illusion of a symmetric network. We describe the communication service of our middleware, the Distribution Subsystem (DSS), which carefully separates connections to remote processes from the protocols that communicate over them. This separation is used to plug-in a peer-to-peer module to provide symmetric and persistent connectivity. The P2P module can provide both up-to-date addresses for mobile processes as well as route discovery to overcome asymmetric links.

Fractional Weighted Reference Counting

We introduce a scheme for distributed garbage collection that is an extension of Weighted Reference Counting. This scheme represents weights as fractions. It solves the problem of limited weight, preserves the property of third-party independence, and does not induce extra messages for reference merging.