Table of Contents
This section is a loose collection of frequently asked questions about the WS MDS. It includes mostly information about what the WS MDS is and what Information Services are included in the Globus Toolkit 4+. The goal is to have it grow over time with common user questions and for this to become a frequently used resource.
Q: What's the difference between Pre-WS MDS, MDS2, WS-MDS, and WS MDS?
A: MDS2 (also known as Pre-WS MDS) was the LDAP based monitoring/discovery/information publishing system implementation distributed with various Globus Toolkit versions starting with GT2. GT4 also includes a deprecated release of MDS2, but its use is generally discouraged due to operational and scalability limitations as well as security issues. WS-MDS (also know as WS MDS) is the more recent WebService based Monitoring and Discovery Service that is fully integrated with the rest of GT4. You can view more information about MDS2 and WS MDS (respectively) here: http://www.globus.org/toolkit/docs/4.0/info/prewsmds/PreWSMDSFacts.html and http://www.globus.org/toolkit/docs/4.0/info/
Q: What is the WS MDS Index Service?
A: The Index Service collects monitoring and discovery information from Grid resources, and publishes it in a single location; generally, it is expected that a virtual organization will deploy one or more index services which will collect data on all of the Grid resources available within that virtual organization. Read more information about it here: http://www.globus.org/toolkit/docs/4.0/info/index/
Q: What is the WS MDS Trigger Service?
A: The Trigger Service collects data from resources on the grid and, if administrator defined rules match, can perform various actions. An example use is to send email when queue length on a compute resource goes over a threshold value. Read more information about it here: http://www.globus.org/toolkit/docs/4.0/info/trigger/
Q: How do I query the WS MDS Index?
A: There are a number of ways to access the information in the Index Service. The most common is using the command line tools described here: http://www.globus.org/toolkit/docs/4.0/info/index/user-index.html Some common queries are also described here: http://www-unix.mcs.anl.gov/~robertm/xpath-queries.html You can also access the information programmatically using the Java based API See http://www.globus.org/api/javadoc-4.0/globus_java_ws_core/org/globus/wsrf/query/package-tree.html for some more detail.
Q: I've already installed Ganglia/Hawkeye, but it isn't showing up in the WS MDS Index when I start it. How do I configure the Index so that the Ganglia or Hawkeye data is in it?
A: Read how to configure either of these here: http://globus.org/toolkit/docs/4.0/info/key/gluerp.html
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