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Service Scheduler in a Trustworthy Web Server Yinong Chen 1 Assumptions Use off-the-shelf client software Use .Net framework .Net framework cannot be modified Not use off-the-shelf web server, e.g. MS IIS (Internet Information Service) We will write a simple server software We will write simple service agents 2 Implementation Overview Clients off-the-shelf Web Server Service Provider Agents Service Agents Service Scheduler 3 C# Multithreading in .Net Framework Service Scheduler requests from Service Provider Distributor QS1 QS2 QS3 QS2 Priority queues Service Scheduler Dispatcher (service activator) S1 S3 S2 S4 4 .Net Runtime What Can Be Scheduled Service Scheduling Which service agent should be activated? Will be implemented in the prototype Task Scheduling Which process (all tasks and agents in the system) should be executed? Should be implemented in the infrastructure (OS) Will not be implemented in the prototype 5 Implementation Consideration Each task, agent, or object is a C# thread Threads are organized in a hierarchy The main() will activate two threads: Service Provider, which will activate: • service agents 6 Scheduler, which will activate • distributor • priority queue agents • dispatcher, which will activate the selected service agent Dispatch Policies Select the most critical service first; Dispatch the request with the highest priority; Each service agent will start a quantum timer at the beginning. When timeout, the current process is saved, put back into its queue, and another request is dispatched 7