Strategies for Token Monitoring

Monitoring distributed computations provides a practical way of learning about and coming to understand a class of applications that are becoming increasingly common. The beneets of distribution arise from processes cooperating together to achieve a common goal. Coordination among the processes is a fundamental ingredient for the cooperation to occur both correctly and eeciently. One common form of coordination is token passing, where a token enables the process holding it to perform some action(s). In this paper we examine some of the options available to monitor the process that holds the token , as the token moves from one process to another. The goal is to always be able to report information about whichever process is holding the token while minimizing the amount of perturbation introduced by monitoring. After presenting centralized and distributed strategies for token monitoring we discuss how agents can be employed. This paper also reports on our use of agents within the Pathhnder system to achieve token monitoring.