VisOK: A flexible visualization system for distributed Java object application

Distributed Object Systems are known to be very complex. Consequently it is very difficult, if not impossible, to see the overall relationship among participating objects in the system. That complicates the issues connected with performance tuning and maintenance. An economical way to visualize the system is clearly needed. In this paper, we propose a tracing facility for Java-based distributed object system, especially Java RMI (Remote Method Invocation). Our visualization system VisOK (Visual Object-Kit) uses two-phase hybrid post-mortem/on-the-fly technique. The fundamental tracing part has a flexible and dynamic mechanism. The main idea behind the tracing technique is the Plug-in Sensor Model (PSM). There is a close relationship between tracing part and the visualization part. For effective visualization of a working system, the causality of events has to be preserved. VisOK supports global event ordering. And for collecting and assembling local states of objects, we propose a distributed snapshot algorithm.