The design of the Virtual Grid Execution System (vgES) was a collaboration amongst the entire VGrADS team, including both the Execution System and Programming Tools investigators.  This design was critical both to the notion of Virtual Grids (VGs), defining the two major interfaces between the VGrADS execution system and the programming tools / applications.  In addition, it defined the componentization of the internals of vgES, forming a framework for innovation in the research infrastructure by researchers across the entire VGrADS execution system team.

The system diagram and major components are depicted as follows:



The two major vgES application interfaces include:  1) the VG creation and management APIs through which the application submits a vgDL description, asks the vgES to create the VG, and receives the constructed VG, and 2) the VG itself, which provides an explicit, hierarchical representation of the resources that have been bound into the VG, and also presents all static and dynamic information about those resources through an extensible attribute-based interface.  The VG creation and management interface includes operations for extending, curtailing, and even merging a VG dynamically.  The VG interface provides primitives for navigating the VG structure, defining new attributes, reading attributes, and incorporating new information providers.  Together these two interfaces provide a simple, expressive interface for grid resource management.

The major elements of the vgES system architecture were originally implemented in five major components.   

• vgFAB is a “finder and binder” that performs integrated resource selection and binding.  The vgFAB is the primary implementer of vgDL and encompasses the creation of the VG abstraction.  
• vgAgent provides a critical interface function, retrieving static/dynamic resource information from existing information services systems and supporting the finding and binding in vgFAB, as well as the application access to static and dynamic resource information in the VG.  Currently, this system provides full access to MDS and NWS data.
• vgMON is a distributed monitoring component that tracks resource behavior against application expectations, notifying the application when things vary significantly from expected behavior.
• vgLaunch is an application launcher that initiates the application on the resources bound by vgFAB.  Future implementations may leverage scalable launchers from other research efforts.
• DVCW is the module that encapsulates the Distributed Virtual Computer (developed as part of the OptIPuter project), which in turn encapsulates the standard resource management interfaces provided by Globus.

These five components can each be implemented locally, or as a distributed service.  In addition, this clean factorization enables research and innovation in each of these areas (and above the vgES interface) with moderate effort.  This ensures that vgES serves the important role of providing a research platform for efforts to explore research issues within vgES and those properly framed outside of it.

The first implementation of vgES (version 0.7) was completed in March 2005 and distributed to VGrADS team members. It focused on the vgFAB, vgAgent, and DVCW components to allow its use in simple experiments. It was implemented as a standalone Java program.

Developments in 2006 included the addition of dynamic features (in particular, dynamic VG management) and vgMON capabilities. 2006 also saw the addition of slotted virtual grids, which incorporate start and end times for resource availability.

Because this is an ongoing research system, each of the vgES components is the subject of active research and will likely be reimplemented in several ways to explore new algorithms, grid strategies, or to reflect application needs and perform systematic research experiments.  Indeed, our research in resource selection and allocation has been driven by the requirements of the vgFAB component.

We have received numerous inquiries from large-scale application and infrastructure projects expressing interest in use of vgES in broader settings.  Unfortunately, we cannot accommodate those requests now since VGrADS is a computer science systems research project, with no charter (and insufficient resources) to produce software infrastructure for broader use. We are, however, exploring possibilities for follow-on projects that might be more infrastructure-oriented. If you are interested, please contact one of the VGrADS PIs.