Classified Advertisements

Classified Advertisements (classads) are the lingua franca of Condor. They are used for describing jobs, workstations, and other resources. They are exchanged by Condor processes to schedule jobs. They are logged to files for statistical and debugging purposes. They are used to enquire about current state of the system.

A classad is a mapping from attribute names to expressions. In the simplest cases, the expressions are simple constants (integer, floating point, or string). A classad is thus a form of property list. Attribute expressions can also be more complicated. There is a protocol for evaluating an attribute expression of a classad vis a vis another ad. For example, the expression "other.size > 3" in one ad evaluates to true if the other ad has an attribute named size and the value of that attribute is (or evaluates to) an integer greater than three. Two classads match if each ad has an attribute requirements that evaluates to true in the context of the other ad. Classad matching is used by the Condor central manager to determine the compatibility of jobs and workstations where they may be run.

The classad library is available as a separate stand-alone package for use in applications other than Condor.

If you use the ClassAd library, we encourage you to subscribe to the classad-users mailing list. This list is for discussion among all ClassAd users, and for occasional announcements related to ClassAds. There is a web page for subscribing to the mailing list. At least one of the ClassAd developers reads this mailing list.

Papers and Slides

• Policy Driven Heterogeneous Resource Co-Allocation with Gangmatching Proceedings of the Twelfth IEEE International Symposium on High-Performance Distributed Computing, June, 2003, Seattle, WA.
  Matchmaking extended from two-way to multiway matches, and a variety of techniques to make it fast.
• Matchmaking: Distributed Resource Management for High Throughput Computing Proceedings of the Seventh IEEE International Symposium on High Performance Distributed Computing, July 28-31, 1998, Chicago, IL.
  A high-level overview of the ClassAd language and its use in Condor.
• Matchmaking Frameworks for Distributed Resource Management Ph.d Dissertation of Rajesh Raman, , October 2000
  
• Overview of the ClassAd Language; PostScript slides of language features
• The ClassAd Language Reference Manual. A formal specification of the syntax and semantics of the ClassAd language.
  • Postscript
  • PDF
  • HTML

ClassAd Distribution Downloads

C++ Implementation

• A tutorial for programming the C++ implementation. The tutorial also includes an informal description of the language.
• Documentation of the C++ ClassAd Distribution.
• Version 1.0.3 of the ClassAd library (10-Mar-2008)
  Some bugfixes and build system improvements in this version. Changelog
• Version 1.0.1 of the ClassAd library (1-Dec-2008)
  A few new features and some bugfixes are in this version. Changelog
• Version 0.9.9 of the ClassAd library (15-Jun-2007)
  A few new features and some bugfixes are in this version. Changelog
• Version 0.9.8 of the ClassAd library (14-Jun-2006)
  A few new features and some bugfixes are in this version. Changelog
• Version 0.9.7 of the ClassAd library (28-Oct-2004)
  Very few changes are in this version. Changelog
• Version 0.9.6 of the ClassAd library (07-Oct-2004)
  Many bugfixes are in this version. Changelog

Java Implementation

• Version 1.1
  • API Documentation
  • classad.jar
  • Java ClassAd source
• Verison 2.1
  • API Documentation
  • classad.jar
  • Java ClassAd source
• Verison 2.2
  • API Documentation
  • classad.jar
  • Java ClassAd source
• Version 2.3
  • Documentation: see Version 2.2 above. There were no documentation changes.
  • classad.jar
  • Java ClassAd source
• Version 2.4
  • Documentation: see Version 2.2 above. There were no documentation changes. This version simply fixed a threading error. (Fix contributed by Luigi Zangrando.)
  • classad.jar
  • Java ClassAd source

Sample Applications

• ClassAd Catalog

Acknowledgement