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Dynamic Adaptation of Distributed Systems

Francisco Silva
( brazilian )

University of São Paulo
Av. 9 de Julho, 2021, apto 64, Bela Vista 01313-001 São Paulo - SP
tel: 55+11+2515926
fax:
fssilva@ime.usp.br

Keywords:

distribution frameworks adaptive software

Abstract:

Adaptation techniques allow software to modify its own functions and configuration in response to changes in its execution environment. They are particularly useful in distributed and mobile computing because of the intrinsic characteristics that make their execution environment susceptible to great variations.

In order to incorporate an adaptable behavior, an application must have a way to monitor the execution environment and discover relevant variations than requires reconfiguration.

The developer of an adaptive software must take care of several issues such as the selection of what elements of the environment should be monitored and how to perform the monitoring, what adaptations of the software behavior should be performed and when they should take place.

Our work aims at addressing the problem of how to change computing systems at runtime in order to adapt to variations in the execution environment, such as resource availability and user mobility. Our main interest is on adapting distributed information systems composed of several components spread over a network where data are also decentralized and users are mobile.

We began by designing an object oriented model to serve as a base for the implementation of an adaptation framework that helps building adaptable distributed applications which support dynamic reconfiguration of its components as changes in the execution environment take place.

The model is composed of three main packages. The first is responsible for monitoring the entities present in the system. The data collected by this package is stored in logs or sent directly to the event detection and notification package. The latter is responsible for analyzing that data and determining the occurrence of events in which there is interest. These events are sent to the dynamic reconfiguration package, which is responsible for applying the required reconfiguration actions to adapt the system.

In order to validate the framework we are using as a reference application a prototype derived from the SIDAM project. SIDAM stands for Distributed Information Systems for Mobile Agents. The research aims at studying the main problems related to the design and implementation of decentralized information systems for mobile users. The SIDAM reference application is a distributed information service disseminating road traffic information for a large metropolis.

The SIDAM reference architecture is a interesting example of a highly dynamic and distributed application since the generation, storage and query of information are decentralized and clients are mobile. In this case, adaptation becomes essential for achieving high service availability, dynamic load balancing, and short response times for clients.

The PhD work started: 01/03/1999

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Last modified on Mon Aug 15 14:59:24 2005