A mobile agent model for fault-tolerant manipulation on distributed objects |
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Authors: | Youhei Tanaka Naohiro Hayashibara Tomoya Enokido Makoto Takizawa |
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Institution: | (1) Dept. of Computers and Systems Engineering, Tokyo Denki University, Saitama, Japan;(2) Faculty of Business Administration, Rissho University, Tokyo, Japan |
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Abstract: | In this paper, we discuss how to realize fault-tolerant applications on distributed objects. Servers supporting objects can
be fault-tolerant by taking advantage of replication and checkpointing technologies. However, there is no discussion on how
application programs being performed on clients are tolerant of clients faults. For example, servers might block in the two-phase
commitment protocol due to the client fault. We newly discuss how to make application programs fault-tolerant by taking advantage
of mobile agent technologies where a program can move from a computer to another computer in networks. An application program
to be performed on a faulty computer can be performed on another operational computer by moving the program in the mobile
agent model. In this paper, we discuss a transactional agent model where a reliable and efficient application for manipulating objects in multiple computers is realized in the mobile agent
model. In the transactional agent model, only a small part of the application program named routing subagent moves around computers. A routing subagent autonomously finds a computer which to visit next. We discuss a hierarchical navigation
map which computer should be visited price to another computer in a transactional agent. A routing subagent makes a decision
on which computer visit for the hierarchical navigation map. Programs manipulating objects in a computer are loaded to the
computer on arrival of the routing subagent in order to reduce the communication overhead. This part of the transactional
agent is a manipulating subagent. The manipulation subagent still exists on the computer even after the routing subagent leaves the computer in order to hold
objects until the commitment. We assume every computer may stop by fault while networks are reliable. There are kinds of faulty
computers for a transactional agent; current, destination, and sibling computers where a transactional agent now exists, will move, and has visited, respectively. The types of faults are detected
by neighbouring manipulation subagents by communicating with each other. If some of the manipulation subagents are faulty,
the routing subagent has to be aborted. However, the routing subagent is still moving. We discuss how to efficiently deliver
the abort message to the moving routing subagent. We evaluate the transactional agent model in terms of how long it takes
to abort the routing subagent if some computer is faulty.
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Keywords: | Fault-tolerant Mobile agent model Distributed transaction |
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