added utility to compute the scheduling window. Right now there's only criteria on which this is determined -- fillNextOfferCycle. So, the schedWindow is the max number of tasks, that aren't yet scheduled, whose aggregate resource requirement is as close as possible to the resource available in the next round of resource offers. To be able to make the most use of the next offer cycle, one would need to perform a non-polynomial search of the TaskQueue and as this is computationally expensive, a linear search is performed on the TaskQueue. Retrofitted scheduling policies to also call utilities.schedUtils#schedWindowResizingStrategy#Apply before switching to a new scheduling policy.

power-capping/extrema.go

@@ -1,9 +1,9 @@
 package pcp
 
 import (
+	elecLogDef "bitbucket.org/sunybingcloud/elektron/logging/def"
 	"bitbucket.org/sunybingcloud/elektron/pcp"
 	"bitbucket.org/sunybingcloud/elektron/rapl"
-	elecLogDef "bitbucket.org/sunybingcloud/elektron/logging/def"
 	"bufio"
 	"container/ring"
 	"fmt"
@@ -130,7 +130,7 @@ func StartPCPLogAndExtremaDynamicCap(quit chan struct{}, logging *bool, hiThresh
 							cappedHosts[victim.Host] = true
 							orderCapped = append(orderCapped, victim.Host)
 							logMType <- elecLogDef.GENERAL
-							logMsg <- fmt.Sprintf("Capping Victim %s Avg. Wattage: %f", victim.Host, victim.Watts * pcp.RAPLUnits)
+							logMsg <- fmt.Sprintf("Capping Victim %s Avg. Wattage: %f", victim.Host, victim.Watts*pcp.RAPLUnits)
 							if err := rapl.Cap(victim.Host, "rapl", 50); err != nil {
 								logMType <- elecLogDef.ERROR
 								logMsg <- "Error capping host"

power-capping/progressive-extrema.go

@@ -2,10 +2,10 @@ package pcp
 
 import (
 	"bitbucket.org/sunybingcloud/elektron/constants"
+	elecLogDef "bitbucket.org/sunybingcloud/elektron/logging/def"
 	"bitbucket.org/sunybingcloud/elektron/pcp"
 	"bitbucket.org/sunybingcloud/elektron/rapl"
 	"bitbucket.org/sunybingcloud/elektron/utilities"
-	elecLogDef "bitbucket.org/sunybingcloud/elektron/logging/def"
 	"bufio"
 	"container/ring"
 	"fmt"

rapl/cap.go

@@ -1,11 +1,11 @@
 package rapl
 
 import (
+	elekEnv "bitbucket.org/sunybingcloud/elektron/environment"
 	"github.com/pkg/errors"
 	"golang.org/x/crypto/ssh"
-	"strconv"
 	"os"
-	elekEnv "bitbucket.org/sunybingcloud/elektron/environment"
+	"strconv"
 )
 
 func Cap(host, username string, percentage float64) error {

scheduler.go

@@ -2,9 +2,9 @@ package main
 
 import (
 	"bitbucket.org/sunybingcloud/elektron/def"
+	elecLogDef "bitbucket.org/sunybingcloud/elektron/logging/def"
 	"bitbucket.org/sunybingcloud/elektron/pcp"
 	"bitbucket.org/sunybingcloud/elektron/schedulers"
-        elecLogDef "bitbucket.org/sunybingcloud/elektron/logging/def"
 	"flag"
 	"fmt"
 	"github.com/golang/protobuf/proto"

schedulers/MaxGreedyMins.go

@@ -4,6 +4,7 @@ import (
 	"bitbucket.org/sunybingcloud/elektron/def"
 	"bitbucket.org/sunybingcloud/elektron/utilities/mesosUtils"
 	"bitbucket.org/sunybingcloud/elektron/utilities/offerUtils"
+	"bitbucket.org/sunybingcloud/elektron/utilities/schedUtils"
 	"fmt"
 	mesos "github.com/mesos/mesos-go/api/v0/mesosproto"
 	sched "github.com/mesos/mesos-go/api/v0/scheduler"
@@ -174,6 +175,11 @@ func (s *MaxGreedyMins) ConsumeOffers(spc SchedPolicyContext, driver sched.Sched
 
 	// Switch scheduling policy only if feature enabled from CLI
 	if baseSchedRef.schedPolSwitchEnabled {
+		// Need to recompute the schedWindow for the next offer cycle.
+		// The next scheduling policy will schedule at max schedWindow number of tasks.
+		baseSchedRef.schedWindow = schedUtils.
+			SchedWindowResizingCritToStrategy[baseSchedRef.schedWindowResizeCrit].Apply(
+			func() interface{} { return baseSchedRef.tasks })
 		// Switching to a random scheduling policy.
 		// TODO: Switch based on some criteria.
 		index := rand.Intn(len(SchedPolicies))

schedulers/MaxMin.go

@@ -4,6 +4,7 @@ import (
 	"bitbucket.org/sunybingcloud/elektron/def"
 	"bitbucket.org/sunybingcloud/elektron/utilities/mesosUtils"
 	"bitbucket.org/sunybingcloud/elektron/utilities/offerUtils"
+	"bitbucket.org/sunybingcloud/elektron/utilities/schedUtils"
 	"fmt"
 	mesos "github.com/mesos/mesos-go/api/v0/mesosproto"
 	sched "github.com/mesos/mesos-go/api/v0/scheduler"
@@ -168,6 +169,11 @@ func (s *MaxMin) ConsumeOffers(spc SchedPolicyContext, driver sched.SchedulerDri
 
 	// Switch scheduling policy only if feature enabled from CLI
 	if baseSchedRef.schedPolSwitchEnabled {
+		// Need to recompute the schedWindow for the next offer cycle.
+		// The next scheduling policy will schedule at max schedWindow number of tasks.
+		baseSchedRef.schedWindow = schedUtils.
+			SchedWindowResizingCritToStrategy[baseSchedRef.schedWindowResizeCrit].Apply(
+			func() interface{} { return baseSchedRef.tasks })
 		// Switching to a random scheduling policy.
 		// TODO: Switch based on some criteria.
 		index := rand.Intn(len(SchedPolicies))

schedulers/base.go

@@ -4,6 +4,7 @@ import (
 	"bitbucket.org/sunybingcloud/elektron/def"
 	elecLogDef "bitbucket.org/sunybingcloud/elektron/logging/def"
 	"bitbucket.org/sunybingcloud/elektron/utilities"
+	"bitbucket.org/sunybingcloud/elektron/utilities/schedUtils"
 	"bytes"
 	"fmt"
 	"github.com/golang/protobuf/proto"
@@ -55,6 +56,17 @@ type BaseScheduler struct {
 
 	// Whether switching of scheduling policies at runtime has been enabled
 	schedPolSwitchEnabled bool
+
+	// Size of window of tasks that can be scheduled in the next offer cycle.
+	// The window size can be adjusted to make the most use of every resource offer.
+	// By default, the schedulingWindow would correspond to all the remaining tasks that haven't yet been scheduled.
+	schedulingWindow int
+
+	// Criteria to resize the schedulingWindow.
+	schedWindowResizeCrit schedUtils.SchedulingWindowResizingCriteria
+	// Window of tasks that the current scheduling policy has to schedule.
+	// Once #schedWindow tasks are scheduled, the current scheduling policy has to stop scheduling.
+	schedWindow int
 }
 
 func (s *BaseScheduler) init(opts ...schedPolicyOption) {
@@ -66,6 +78,7 @@ func (s *BaseScheduler) init(opts ...schedPolicyOption) {
 	}
 	s.running = make(map[string]map[string]bool)
 	s.mutex = sync.Mutex{}
+	s.schedWindowResizeCrit = "fillNextOfferCycle"
 }
 
 func (s *BaseScheduler) SwitchSchedPol(newSchedPol SchedPolicyState) {

schedulers/bin-packing.go

@@ -4,6 +4,7 @@ import (
 	"bitbucket.org/sunybingcloud/elektron/def"
 	"bitbucket.org/sunybingcloud/elektron/utilities/mesosUtils"
 	"bitbucket.org/sunybingcloud/elektron/utilities/offerUtils"
+	"bitbucket.org/sunybingcloud/elektron/utilities/schedUtils"
 	"fmt"
 	mesos "github.com/mesos/mesos-go/api/v0/mesosproto"
 	sched "github.com/mesos/mesos-go/api/v0/scheduler"
@@ -118,6 +119,11 @@ func (s *BinPackSortedWatts) ConsumeOffers(spc SchedPolicyContext, driver sched.
 
 	// Switch scheduling policy only if feature enabled from CLI
 	if baseSchedRef.schedPolSwitchEnabled {
+		// Need to recompute the schedWindow for the next offer cycle.
+		// The next scheduling policy will schedule at max schedWindow number of tasks.
+		baseSchedRef.schedWindow = schedUtils.
+			SchedWindowResizingCritToStrategy[baseSchedRef.schedWindowResizeCrit].Apply(
+			func() interface{} { return baseSchedRef.tasks })
 		// Switching to a random scheduling policy.
 		// TODO: Switch based on some criteria.
 		index := rand.Intn(len(SchedPolicies))

schedulers/first-fit.go

@@ -4,6 +4,7 @@ import (
 	"bitbucket.org/sunybingcloud/elektron/def"
 	"bitbucket.org/sunybingcloud/elektron/utilities/mesosUtils"
 	"bitbucket.org/sunybingcloud/elektron/utilities/offerUtils"
+	"bitbucket.org/sunybingcloud/elektron/utilities/schedUtils"
 	"fmt"
 	mesos "github.com/mesos/mesos-go/api/v0/mesosproto"
 	sched "github.com/mesos/mesos-go/api/v0/scheduler"
@@ -103,6 +104,11 @@ func (s *FirstFit) ConsumeOffers(spc SchedPolicyContext, driver sched.SchedulerD
 
 	// Switch scheduling policy only if feature enabled from CLI
 	if baseSchedRef.schedPolSwitchEnabled {
+		// Need to recompute the schedWindow for the next offer cycle.
+		// The next scheduling policy will schedule at max schedWindow number of tasks.
+		baseSchedRef.schedWindow = schedUtils.
+			SchedWindowResizingCritToStrategy[baseSchedRef.schedWindowResizeCrit].Apply(
+			func() interface{} { return baseSchedRef.tasks })
 		// Switching to a random scheduling policy.
 		// TODO: Switch based on some criteria.
 		index := rand.Intn(len(SchedPolicies))

schedulers/helpers.go

@@ -125,7 +125,7 @@ func WithSchedPolSwitchEnabled(enableSchedPolicySwitch bool) schedPolicyOption {
 	}
 }
 
-// Launch tasks.
+// Launch tasks and also update the resource availability for the corresponding host.
 func LaunchTasks(offerIDs []*mesos.OfferID, tasksToLaunch []*mesos.TaskInfo, driver sched.SchedulerDriver) error {
 	driver.LaunchTasks(offerIDs, tasksToLaunch, mesosUtils.DefaultFilter)
 	// Update resource availability

schedulers/store.go

@@ -6,18 +6,18 @@ import (
 
 // Names of different scheduling policies.
 const (
-	ff          = "first-fit"
-	bp          = "bin-packing"
-	mgm         = "max-greedymins"
-	mm          = "max-min"
+	ff  = "first-fit"
+	bp  = "bin-packing"
+	mgm = "max-greedymins"
+	mm  = "max-min"
 )
 
 // Scheduling policy factory
 var SchedPolicies map[string]SchedPolicyState = map[string]SchedPolicyState{
-	ff:          &FirstFit{},
-	bp:          &BinPackSortedWatts{},
-	mgm:         &MaxGreedyMins{},
-	mm:          &MaxMin{},
+	ff:  &FirstFit{},
+	bp:  &BinPackSortedWatts{},
+	mgm: &MaxGreedyMins{},
+	mm:  &MaxMin{},
 }
 
 // build the scheduling policy with the options being applied

utilities/schedUtils/schedUtils.go

@@ -0,0 +1,63 @@
+package schedUtils
+
+import (
+	"bitbucket.org/sunybingcloud/elektron/def"
+	"bitbucket.org/sunybingcloud/elektron/utilities"
+)
+
+// Criteria for resizing the scheduling window.
+type SchedulingWindowResizingCriteria string
+
+var SchedWindowResizingCritToStrategy = map[SchedulingWindowResizingCriteria]schedWindowResizingStrategy{
+	"fillNextOfferCycle": &fillNextOfferCycle{},
+}
+
+// Interface for a scheduling window resizing strategy.
+type schedWindowResizingStrategy interface {
+	// Apply the window resizing strategy and return the news scheduling window size.
+	Apply(func() interface{}) int
+}
+
+// Scheduling window resizing strategy that attempts to resize the scheduling window
+// to include as many tasks as possible so as to make the most use of the next offer cycle.
+type fillNextOfferCycle struct{}
+
+func (s *fillNextOfferCycle) Apply(getArgs func() interface{}) int {
+	return s.apply(getArgs().([]def.Task))
+}
+
+// Loop over the unscheduled tasks, in submission order, and determine the maximum
+// number of tasks that can be scheduled in the next offer cycle.
+// As the offers get smaller and smaller, this approach might lead to an increase in internal fragmentation.
+//
+// Note: To be able to make the most use of the next offer cycle, one would need to perform a non-polynomial search
+// which is computationally expensive.
+func (s *fillNextOfferCycle) apply(taskQueue []def.Task) int {
+	clusterwideResourceCount := utilities.GetClusterwideResourceAvailability()
+	newSchedWindow := 0
+	filledCPU := 0.0
+	filledRAM := 0.0
+
+	// Can we schedule another task.
+	canSchedule := func(t def.Task) bool {
+		if ((filledCPU + t.CPU) <= clusterwideResourceCount.UnusedCPU) &&
+			((filledRAM + t.RAM) <= clusterwideResourceCount.UnusedRAM) {
+			return true
+		}
+		return false
+	}
+
+	for _, task := range taskQueue {
+		for i := *task.Instances; i > 0; i-- {
+			if canSchedule(task) {
+				filledCPU += task.CPU
+				filledRAM += task.RAM
+				newSchedWindow++
+			} else {
+				break
+			}
+		}
+		break
+	}
+	return newSchedWindow
+}