added a baseSchedPolicyState struct in schedulers/schedPolicy.go. This struct would store information common to scheduling policies. Added member called numTasksScheduled to baseSchedPolicyState that would keep count of the number of tasks that the current scheduling policy has scheduled. Moved the logic to switch (currently performing a random switch) to baseSchedPolicyState#switchIfNecessary(...) and retrofitted all scheduling policies to call this instead of inlining the code in each of them.

schedulers/schedPolicy.go

@@ -3,6 +3,7 @@ package schedulers
 import (
 	mesos "github.com/mesos/mesos-go/api/v0/mesosproto"
 	sched "github.com/mesos/mesos-go/api/v0/scheduler"
+	"math/rand"
 )
 
 type SchedPolicyContext interface {
@@ -14,3 +15,35 @@ type SchedPolicyState interface {
 	// Define the particular scheduling policy's methodology of resource offer consumption.
 	ConsumeOffers(SchedPolicyContext, sched.SchedulerDriver, []*mesos.Offer)
 }
+
+type baseSchedPolicyState struct {
+	SchedPolicyState
+	// Keep track of the number of tasks that have been scheduled.
+	numTasksScheduled int
+}
+
+func (bsps *baseSchedPolicyState) switchIfNecessary(spc SchedPolicyContext) {
+	baseSchedRef := spc.(*BaseScheduler)
+	// Switch scheduling policy only if feature enabled from CLI
+	if baseSchedRef.schedPolSwitchEnabled {
+		// Need to recompute schedulWindow for the next offer cycle.
+		// The next scheduling policy will schedule at max schedWindow number of tasks.
+		baseSchedRef.curSchedWindow = baseSchedRef.schedWindowResStrategy.Apply(
+			func() interface{} { return baseSchedRef.tasks })
+		// Switching to a random scheduling policy.
+		// TODO: Switch based on some criteria.
+		index := rand.Intn(len(SchedPolicies))
+		for _, v := range SchedPolicies {
+			if index == 0 {
+				spc.SwitchSchedPol(v)
+				// If switched to a different scheduling policy,
+				// then setting the numberTasksScheduled to 0.
+				if v != bsps {
+					bsps.numTasksScheduled = 0
+				}
+				break
+			}
+			index--
+		}
+	}
+}