An approach to rollback recovery of collaborating mobile agents

Fault-tolerance is one of the main problems that must be resolved to improve the adoption of the agents' computing paradigm. In this paper, we analyse the execution model of agent platforms and the significance of the faults affecting their constituent components on the reliable execution of agent-based applications, in order to develop a pragmatic framework for agent systems fault-tolerance. The developed framework deploys a communication-pairs independent check pointing strategy to offer a low-cost, application-transparent model for reliable agent- based computing that covers all possible faults that might invalidate reliable agent execution, migration and communication and maintains the exactly-one execution property

DNAgents: Genetically Engineered Intelligent Mobile Agents

Mobile agents are a useful paradigm for network coding providing many advantages and disadvantages. Unfortunately, widespread adoption of mobile agents has been hampered by the disadvantages, which could be said to outweigh the advantages. There is a variety of ongoing work to address these issues, and this is discussed. Ultimately, genetic algorithms are selected as the most interesting potential avenue. Genetic algorithms have many potential benefits for mobile agents. The primary benefit is the potential for agents to become even more adaptive to situational changes in the environment and/or emergent security risks. There are secondary benefits such as the natural obfuscation of functions inherent to genetic algorithms. Pitfalls also exist, namely the difficulty of defining a satisfactory fitness function and the variable execution time of mobile agents arising from the fact that it exists on a network. DNAgents 1.0, an original application of genetic algorithms to mobile agents is implemented and discussed, and serves to highlight these difficulties. Modifications of traditional genetic algorithms are also discussed. Ultimately, a combination of genetic algorithms and artificial life is considered to be the most appropriate approach to mobile agents. This allows the consideration of agents to be organisms, and the network to be their environment. Towards this end, a novel framework called DNAgents 2.0 is designed and implemented. This framework allows the continual evolution of agents in a network without having a seperate training and deployment phase. Parameters for this new framework were defined and explored. Lastly, an experiment similar to DNAgents 1.0 is performed for comparative purposes against DNAgents 1.0 and to prove the viability of this new framework

Envelhecimento e rejuvenescimento de software: 20 anos (19952014) - panorama e desafios

Although software aging and rejuvenation is a young research held, in its first 20 years a lot of knowledge has been produced. Nowadays, important scientific journals and conferences include SAR-related topics in their scope of interest. This fast growing and wide range of dissemination venues pose a challenge to researchers to keep tracking of the new findings and trends in this area. In this work, we collected and analyzed SAR research data to detect trends, patterns, and thematic gaps, in order to provide a comprehensive view of this research held over its hrst 20 years. Adopted the systematic mapping approach to answer research questions such as: How the main topics investigated in SAR have evolved over time? Which are the most investigated aging effects? Which rejuvenation techniques and strategies are more frequently used?CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorDissertação (Mestrado)Embora o envelhecimento e rejuvenescimento de software seja um campo de pesquisa novo, em seus primeiros 20 anos muito conhecimento foi produzido. Hoje em dia, revistas e conferências científicas importantes incluem temas relacionados a SAR no seu âmbito de interesse. Este crescimento rápido e a grande variedade de locais de disseminação representam um desafio para os pesquisadores para manter o acompanhamento das novas descobertas e tendências nesta área. Neste trabalho, foram coletados e analisados dados de pesquisa em SAR para detectar tendências, padrões e lacunas temáticas, a hm de proporcionar uma visão abrangente deste campo de pesquisa em seus primeiros 20 anos. Adotou-se a abordagem de mapeamento sistemático para responder a perguntas de pesquisa, tais como: Como os principais temas investigados em SAR têm evoluído ao longo do tempo? Quais são os efeitos do envelhecimento mais investigados? Quais técnicas e estratégias de rejuvenescimento são mais frequentemente usadas

Using mobility and exception handling to achieve mobile agents that survive server crash failures

Mobile agent technology, when designed and used effectively, can minimize bandwidth consumption and autonomously provide a snapshot of the current context of a distributed system. Protecting mobile agents from server crashes is a challenging issue, since developers normally have no control over remote servers. Server crash failures can leave replicas, instable storage, unavailable for an unknown time period. Furthermore, few systems have considered the need for using a fault tolerant protocol among a group of collaborating mobile agents. This thesis uses exception handling to protect mobile agents from server crash failures. An exception model is proposed for mobile agents and two exception handler designs are investigated. The first exists at the server that created the mobile agent and uses a timeout mechanism. The second, the mobile shadow scheme, migrates with the mobile agent and operates at the previous server visited by the mobile agent. A case study application has been developed to compare the performance of the two exception handler designs. Performance results demonstrate that although the second design is slower it offers the smaller trip time when handling a server crash. Furthermore, no modification of the server environment is necessary. This thesis shows that the mobile shadow exception handling scheme reduces complexity for a group of mobile agents to survive server crashes. The scheme deploys a replica that monitors the server occupied by the master, at each stage of the itinerary. The replica exists at the previous server visited in the itinerary. Consequently, each group member is a single fault tolerant entity with respect to server crash failures. Other schemes introduce greater complexity and performance overheads since, for each stage of the itinerary, a group of replicas is sent to servers that offer an equivalent service. In addition, future research is established for fault tolerance in groups of collaborating mobile agents

Fault-tolerant and transactional mobile agent execution

Mobile agents constitute a computing paradigm of a more general nature than the widely used client/server computing paradigm. A mobile agent is essentially a computer program that acts autonomously on behalf of a user and travels through a network of heterogeneous machines. However, the greater flexibility of the mobile agent paradigm compared to the client/server computing paradigm comes at additional costs. These costs include, among others, the additional complexity of developing and managing mobile agent-based applications. This additional complexity comprises such issues as reliability. Before mobile agent technology can appear at the core of tomorrow's business applications, reliability mechanisms for mobile agents must be established. In this context, fault tolerance and transaction support are mechanisms of considerable importance. Various approaches to fault tolerance and transaction support exist. They have different strengths and weaknesses, and address different environments. Because of this variety, it is often difficult for the application programmer to choose the approach best suited to an application. This thesis introduces a classification of current approaches to fault-tolerant and transactional mobile agent execution. The classification, which focuses on algorithmic aspects, aims at structuring the field of fault-tolerant and transactional mobile agent execution and facilitates an understanding of the properties and weaknesses of particular approaches. In a distributed system, any software or hardware component may be subject to failures. A single failing component (e.g., agent or machine) may prevent the agent from proceeding with its execution. Worse yet, the current state of the agent and even its code may be lost. We say that the agent execution is blocked. For the agent owner, i.e., the person or application that has configured the agent, the agent does not return. To achieve fault-tolerance, the agent owner can try to detect the failure of the agent, and upon such an event launch a new agent. However, this requires the ability to correctly detect the crash of the agent, i.e., to distinguish between a failed agent and an agent that is delayed by slow processors or slow communication links. Unfortunately, this cannot be achieved in systems such as the Internet. An agent owner who tries to detect the failure of the agent thus cannot prevent the case in which the agent is mistakenly assumed to have crashed. In this case, launching a new agent leads to multiple executions of the agent, i.e., to the violation of the desired exactly-once property of agent execution. Although this may be acceptable for certain applications (e.g., applications whose operations do not have side-effects), others clearly forbid it. In this context, launching a new agent is a form of replication. In general, replication prevents blocking, but may lead to multiple executions of the agent, i.e., to a violation of the exactly-once execution property. This thesis presents an approach that ensures the exactly-once execution property using a simple principle: the mobile agent execution is modeled as a sequence of agreement problems. This model leads to an approach based on two well-known building blocks: consensus and reliable broadcast. We validate this approach with the implementation of FATOMAS, a Java-based FAult-TOlerant Mobile Agent System, and measure its overhead. Transactional mobile agents execute the mobile agent as a transaction. Assume, for instance, an agent whose task is to buy an airline ticket, book a hotel room, and rent a car at the flight destination. The agent owner naturally wants all three operations to succeed or none at all. Clearly, the rental car at the destination is of no use if no flight to the destination is available. On the other hand, the airline ticket may be useless if no rental car is available. The mobile agent's operations thus need to execute atomically, i.e., either all of them or none at all. Execution atomicity also needs to be ensured in the event of failures of hardware or software components. The approach presented in this thesis is non-blocking. A non-blocking transactional mobile agent execution has the important advantage that it can make progress despite failures. In a blocking transactional mobile agent execution, by contrast, progress is only possible when the failed component has recovered. Until then, the acquired locks generally cannot be freed. As no other transactional mobile agents can acquire the lock, overall system throughput is dramatically reduced. The present approach reuses the work on fault-tolerant mobile agent execution to prevent blocking. We have implemented the proposed approach and present the evaluation results

Specification of Fault-Tolerant Mobile Agent Execution and its Building Block

Mobile agent technology is one of the fastest growing areas of research for application development on the Internet today. The potential of mobile agents to perform many tasks, from the menial and routine, to the more complex ones has been widely recognized and thus spurred. However, the lack of a fault tolerant infrastructure and methodologies that address fault tolerant execution of mobile agents highlights a major draw back of this technology. In this paper, we explore the conditions of fault tolerant mobile agent execution and investigate a possible building block for a faulttolerant execution platform.

Analysis of mobile agents' fault-tolerant behavior

The original publication is available at www.springerlink.comMobile agent-based technology has attracted considerable interest in both academia and industry in recent years. Many agent-based execution models have been proposed and their effectiveness have been demonstrated in the literature. However, these models require a high overhead to achieve the reliable execution of mobile agents. In this paper, we propose a new mobile agent-based execution model. Extensive theoretical analysis on the population distribution of mobile agents is provided to evaluate the performance of our model. The analytical results reveal new theoretical insights into the fault-tolerant execution of mobile agents. Our model provides an efficient way to increase overall performance and a promising method in achieving mobile agent system reliability.Wenyu Qu and Hong She

Providing Reliability for transactional mobile agents

International audienceA transactional agent is a mobile agent which migrates from a site to another site to execute a distributed transaction assigned by a user. Works on transactional mobile agents have identified two problems that can't be solved by the agent alone. The first one is related to the reliability. The lack of a fault tolerant infrastructure and methodologies that address fault tolerant execution of mobile agents highlights a major drawback of this technology. The second problem for which the agent needs assistance is related to the atomic validation of the transaction. In this paper we address mobile agent fault tolerance and a transactional support.Un agent transactionnel est un agent mobile qui migre d'un site à un autre pour exécuter une transaction qui lui a été confiée par un utilisateur. Les travaux sur les agents mobiles transactionnels ont identifié deux problèmes qui ne peuvent être résolu uniquement par l'agent. Le premier est lié à la fiabilité. L'absence d'infrastructure et de méthodologie permettant de rendre les agents tolérants aux défaillances est un premier problème. La deuxième raison pour laquelle un agent a besoin d'une aide extérieure est liée au problème de la validation atomique