Abstract. The Globus Toolkit Monitoring and Discovery System (MDS4) defines and implements mechanisms for service and resource discovery and monitoring in distributed environments. MDS4 is distinguished from previous similar systems by its extensive use of interfaces and behaviors defined in the WS-Resource Framework and WS-Notification specifications, and by its deep integration into essentially every component of the Globus Toolkit. We describe the MDS4 architecture and the Web service interfaces and behaviors that allow users to discover resources and services, monitor resource and service states, receive updates on current status, and visualize monitoring results. We present two current deployments to provide insights into the functionality that can be achieved via the use of these mechanisms. The resources available to a virtual organization (VO) in a Grid environment can change frequently as new resources and services are added and old ones are removed or become inaccessible. In addition, resource and service properties may change: for example, when a data server is upgraded to larger capacity, different access rates, or different access protocols. These dynamic behaviors can make both discovery-the process of finding suitable resources to perform a task-and monitoring-the process of observing resources or services to track their status for purposes such as fixing problems and tracking usage-significant undertakings. Typical monitoring and discovery use cases include providing data so that resource brokers can locate computing elements appropriate for a job, streaming data to a steering application so that adjustments can be made to a running application, and notifying system administrators when changes in system load or disk space availability occur, in order to identify possible performance anomalies. The Globus Toolkit's solution to these closely related problems is its Monitoring and Discovery System (MDS): a suite of components for monitoring and discovering resources and services. MDS4, the version in the Globus Toolkit 4 [1], uses standard interfaces defined within the WS-Resource Framework (WSRF) and WS-Notification (WS-N) specifications [2] to provide query and subscription interfaces to arbitrarily detailed resource data (modeled in XML). MDS4 builds heavily on capabilities provided by the WSRF and WS-N specifications; indeed, it can be viewed as an exemplary use case for those specifications, which define the mechanisms used to describe information sources, access information via both queries and subscriptions, and manage
The Globus toolkit REF Monitoring and Discovery System (MDS4) has developed a discovery techniques for a distributed systems based on WSRF (Web Services Resource Framework).
A.: Monitoring the grid with the Globus Toolkit MDS4
Journal of Physics Conference Series 46, 521–525
Computer Science