Track resource usage across the cluster. Created utility in utilities/ to track the total and the unused resources for each host in the cluster. Added utility to def/taskUtils.go to retrieve the resource requirement for a given taskID. Decoupled the code, to launch a list of tasks on a set of offerIDs, to schedulers/helpers.go and updated all the scheduling policies to call this function instead of directly calling mesos.SchedulerDriver#LaunchTasks. The resource availability of the cluster is updated at 2 stages -- 1. When the tasks are about to be launched (in schedulers/helpers.go#LaunchTasks), the scheduling policy switching logic will be able to adhere to the update in the resource availability due to the JUST launched tasks and 2. when a terminal status update is received for a task (in schedulers/base.go#statusUpdate).

schedulers/first-fit.go

@@ -71,8 +71,9 @@ func (s *FirstFit) ConsumeOffers(spc SchedPolicyContext, driver sched.SchedulerD
 				tasks = append(tasks, taskToSchedule)
 
 				baseSchedRef.LogTaskStarting(&task, offer)
-				driver.LaunchTasks([]*mesos.OfferID{offer.Id}, tasks, mesosUtils.DefaultFilter)
-
+				if err := LaunchTasks([]*mesos.OfferID{offer.Id}, tasks, driver); err != nil {
+					baseSchedRef.LogElectronError(err)
+				}
 				offerTaken = true
 
 				baseSchedRef.LogSchedTrace(taskToSchedule, offer)