1 Service Scheduler in a Trustworthy Web Server Yinong Chen

2 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

3 Implementation Overview Clients off-the-shelf Service Provider Agents Service Agents Service Scheduler C# Multithreading in.Net Framework Web Server

4 Service Scheduler Distributor Priority queues S1S3S2S4 requests from Service Provider Q S1 Q S2 Q S3 Q S2 Service Scheduler.Net Runtime Dispatcher (service activator)

5 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

6 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  Scheduler, which will activate distributor priority queue agents dispatcher, which will activate the selected service agent

7 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