RTZen: Highly Predictable, Real-Time Java Middleware for Distributed and Embedded Systems

Distributed real-time and embedded (DRE) applications possess stringent quality of service (QoS) requirements, such as predictability, latency, and throughput constraints. Real-Time CORBA, an open middleware standard, allows DRE applications to allocate, schedule, and control resources to ensure predictable end-to-end QoS. The Real-Time Specification for Java (RTSJ) has been developed to provide extensions to Java so that it can be used for real-time systems, in order to bring Java's advantages, such as portability and ease of use, to real-time applications.In this paper, we describe RTZen, an implementation of a Real-Time CORBA Object Request Broker (ORB), designed to comply with the restrictions imposed by RTSJ. RTZen is designed to eliminate the unpredictability caused by garbage collection and improper support for thread scheduling through the use of appropriate data structures, threading models, and memory scopes. RTZen's architecture is also designed to hide the complexities of RTSJ related to distributed programming from the application developer. Empirical results show that RTZen is highly predictable and has acceptable performance. RTZen therefore demonstrates that Real-Time CORBA middleware implemented in real-time Java can meet stringent QoS requirements of DRE applications, while supporting safer, easier, cheaper, and faster development in real-time Java

Adaptive Quality of Service Control in Distributed Real-Time Embedded Systems

An increasing number of distributed real-time embedded systems face the critical challenge of providing Quality of Service (QoS) guarantees in open and unpredictable environments. For example, such systems often need to enforce CPU utilization bounds on multiple processors in order to avoid overload and meet end-to-end dead-lines, even when task execution times deviate significantly from their estimated values or change dynamically at run-time. This dissertation presents an adaptive QoS control framework which includes a set of control design methodologies to provide robust QoS assurance for systems at different scales. To demonstrate its effectiveness, we have applied the framework to the end-to-end CPU utilization control problem for a common class of distributed real-time embedded systems with end-to-end tasks. We formulate the utilization control problem as a constrained multi-input-multi-output control model. We then present a centralized control algorithm for small or medium size systems, and a decentralized control algorithm for large-scale systems. Both algorithms are designed systematically based on model predictive control theory to dynamically enforce desired utilizations. We also introduce novel task allocation algorithms to ensure that the system is controllable and feasible for utilization control. Furthermore, we integrate our control algorithms with fault-tolerance mechanisms as an effective way to develop robust middleware systems, which maintain both system reliability and real-time performance even when the system is in face of malicious external resource contentions and permanent processor failures. Both control analysis and extensive experiments demonstrate that our control algorithms and middleware systems can achieve robust utilization guarantees. The control framework has also been successfully applied to other distributed real-time applications such as end-to-end delay control in real-time image transmission. Our results show that adaptive QoS control middleware is a step towards self-managing, self-healing and self-tuning distributed computing platform

Timed Automata Models for Principled Composition of Middleware

Middleware for Distributed Real-time and Embedded (DRE) systems has grown more and more complex in recent years due to the varying functional and temporal requirements of complex real-time applications. To enable DRE middleware to be configured and customized to meet the demands of different applications, a body of ongoing research has focused on applying model-driven development techniques to developing QoS-enabled middleware. While current approaches for modeling middleware focus on easing the task of as-assembling, deploying and configuring middleware and middleware-based applications, a more formal basis for correct middleware composition and configuration in the context of individual applications is needed. While the modeling community has used application-level formal models that are more abstract to uncover certain flaws in system design, a more fundamental and lower-level set of models is needed to be able to uncover more subtle safety and timing errors introduced by interference between application computations, particularly in the face of alternative concurrency strategies in the middleware layer. In this research, we have examined how detailed formal models of lower-level middle-ware building blocks provide an appropriate level of abstraction both for modeling and synthesis of a variety of kinds of middleware from these building blocks. When combined with model checking techniques, these formal models can help developers in composing correct combinations of middleware mechanisms, and configuring those mechanisms for each particular application

A framework for configuration and management of resources and components in open distributed multimedia systems

Orientador: Mauricio Ferreira MagalhãesTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: Em sistemas multimídia distribuídos existe uma diversidade de dispositivos de hardware, sistemas operacionais e tecnologias de comunicação. Para tratar os requisitos destas aplicações, os componentes do sistema precisam interagir entre eles considerando os aspectos de QoS de cada um dos elementos envolvidos. Neste contexto, esta tese apresenta o Cosmos ? um framework baseado em componentes proposto para dar suporte à configuração e gerenciamento de recursos em sistemas multimídia. Como prova de conceito do Cosmos, o framework definido foi usado no projeto do middleware AdapTV ? um middleware para sistemas de televisão digital interativa. O projeto do AdapTV explora os principais componentes dos modelos que foram definidos no Cosmos: o modelo de descrição de aplicações de forma independente de linguagens; o modelo de interconexão, que trata as questões de comunicação entre componentes heterogêneos usando diferentes tecnologias de comunicação; e o modelo de gerenciamento de QoS, que permite o monitoramento e a adaptação do sistema. Estes modelos foram explorados na implementação de um protótipo do middleware AdapTV e de uma aplicação distribuída que realiza a captura, transmissão e apresentação de um fluxo de vídeo. Para dar suporte à reusabilidade, o modelo explora o conceito de propriedades para estabelecer acordos de configuração (estáticos e dinâmicos) envolvendo negociações entre os requisitos dos componentes e as características da plataformaAbstract: Distributed multimedia applications involve a diversity of hardware devices, operating systems and communication technologies. In order to fulfill the requirements of such applications, their constituting components need to interact with each other, as well as to consider QoS issues related to devices and transmission media. In such a context, this thesis presents the Cosmos component-based framework for configuration and management of resources of open, distributed multimedia systems. As a proof of concept, the framework was used in the design of the AdapTV middleware ? a middleware for interactive television which explores the major components of the Cosmos, including: the model to describe and represent applications independently of language aspects; the interconnection model that allows communication between components in heterogeneous and distributed multimedia environments; and the QoS management model that provides support for adaptation in the middleware player, triggered by QoS and user requirements changes. These models have been explored in the implementation of a prototype, which includes the AdapTV middleware and a distributed application example that captures, transmits and presents a video flow. In order to provide a generic and reusable approach, and to establish configuration agreements among component requirements and platform features, the framework explores the concept of propertiesDoutoradoEngenharia de ComputaçãoDoutor em Engenharia Elétric