Hiding Grid Resources Behind Brokers

Grid computing is a relatively new and promising research area. Many problems regarding its deployment are still been studied and are not clearly solved yet. Scheduling on the grid is particular challenging since new aspects must be taken into account, such as grid size (which can be huge), heterogeneity of resources and their ownership by different entities. Globus Toolkit, perhaps the most successful grid infrastructure, copes with the scheduling on the grid problem with a solution that involves resource managers and brokers. Brokers schedule applications to resources that can only be accessed by their resource managers. The GRAM module is a uniform interface to different resource managers. Resources from different nature must adhere to the GRAM interface in order to be part of the grid. However, we found that GRAM interface is not enough to hide resource’s details from the GRAM client. Moreover, we found it extremely hard to place GRAM before intermittent resources (i.e. computational resources that appear and disappear with no previous notice, have unknown and varying power and may return incorrect results. Our proposal is to use the broker itself to hide heterogeneous resources. The broker communicates with the resources through a small set of methods necessary to perform its work. This approach is especially attractive when resources cannot cater for arbitrary applications (as with intermittent resources) and could largely simplify the deployment of the grid. We have used MyGrid broker, a grid computing solution for Bag-of-Tasks applications (i.e. those parallel applications whose tasks are independent) to implement these ideas. This broker, exposed as a compliant OGSA/OGSI grid service, was able to access heterogeneous resources, including intermittent resources as well as GRAM/fork resources.