| Summary: | This paper presents the results and experiences of adapting and improving the Many-Task Computing (MTC) framework Kestrel for use with bag of tasks applications and the STAR experiment in particular. Kestrel is a lightweight, highly available job scheduling framework for Virtual Organization Clusters (VOCs) constructed in the cloud. Kestrel uses the Extensible Message and Presence Protocol (XMPP) for increasing MTC platform scalability and mitigating faults in Wide Area Network (WAN) communications. Kestrel's architecture is based upon pilot job frameworks used extensively in Grid computing, with fault-tolerant communications inspired by command-and-control botnets. The extensibility of XMPP has allowed development of protocols for identifying manager nodes, discovering the capabilities of worker agents, and for distributing tasks. Presence notifications provided by XMPP allow Kestrel to monitor the global state of the pool and to perform task dispatching based on worker availability. Since its inception, Kestrel has been modified based on its performance managing operational scientific workloads from the STAR group at Brookhaven National Laboratories. STAR provided a virtual machine image with applications for simulating proton collisions using PYTHIA and GEANT3. A Kestrel-based Virtual Organization Cluster, created on top of Clemson University's Palmetto cluster, CERN, and Amazon EC2, was able to provide over 400,000 CPU hours of computation over the course of a month using an average of 800 virtual machine instances every day, generating nearly seven terabytes of data and the largest PYTHIA production run that STAR has achieved to date.
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