title: Resource scheduling application
body: <p>I'm trying to implement an application that coordinates multiple users who are scheduling exclusive resources. The schedule data must maintain strong consistency over a network with a single master node. The scheduled resources could be anything from a conference room to a worker on a job site.</p>
  
  <p>We assume the conference room cannot be scheduled for two meetings at once and a worker cannot be on two job sites at the same time.  The business logic of the application must not allow a user to "overbook" a resource.</p>
  
  <p>What I can't figure out is how to represent the data so that if two or more users operate on the schedule at the same time, and there are conflicts, one of the updates will abort.</p>
  
  <p>The only solution I've seen so far is to track time slots for each exclusionary resource. So if the conference room is used on 5 min intervals, and it was scheduled for 9-9:30am, then the corresponding 5 minute time slots for 9-9:30am would all return TRUE, while the unscheduled slots would return FALSE or NULL.  The DB transaction would then pull the conference room object out of the store, check all the time slots, and abort if the update conflicted with existing time slots.</p>
  
  <p>However, this seems like it will get really big, really fast.  Perhaps it could be garbage collected?  Also, one of the goals of the design is to support variable granularity, so some objects will get scheduled on a minute to minute basis while others could be on a day to day basis, and this data design does not support that very well.</p>
  
  <p>Currently, I am trying to implement this on Google App Engine using Python, but I would be really interested to see some more general solutions to this problem.  All I've come up with Googling is scheduling recurring tasks, or algorithms that perform one time operations to automatically build optimized schedules.</p>