A HYBRID MONITOR FOR BEHAVIOR AND PERFORMANCE ANALYSIS OF DISTRIBUTED SYSTEMS

This paper describes a hybrid monitor for measuring the performance and observing the behavior of distributed systems during execution. Major problems are the interference of the monitoring system with the system to be monitored and the presentation of meaningful data to users. Monitoring becomes even more difficult in distributed systems since these systems feature asynchronous concurrent activities, nondeterministic behavior and lack central control, precise global time and accurate global state. We emphasize the data collection, analysis and presentation of execution data. A special hardware support, which consists of a test and measurement processor (TMP), was designed and has been implemented in the nodes of an experimental multicomputer system consisting of eleven nodes. The operations of the TMP are completely transparent with a minimal, less than 0.1 percent, overhead to the measured system. In the experimental system, all the TMP's were connected with a central monitoring station, using an independent communication network, in order to provide a global view of the monitored system. The central monitoring station displays the resulting information in easy-to-read charts and graphs. Our experience with the TMP shows that it promotes an improved understanding of run-time behavior and performance measurements, to derive qualitative and quantitative assessments of distributed systems. © 1990 IEEE