Merged in hostsConstantUpdation (pull request #15)

Dynamic updation of constant.Hosts and constants.PowerClasses.

Approved-by: Renan DelValle <rdelval1@binghamton.edu>
Approved-by: Pradyumna Kaushik <pkaushi1@binghamton.edu>

README.md

@@ -8,9 +8,8 @@ To Do:
  * Add ability to use constraints
  * Running average calculations https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
  * Make parameters corresponding to each scheduler configurable (possible to have a config template for each scheduler?)
- * TODO : Adding type of scheduler to be used, to be picked from a config file, along with it's configurable parameters.
+ * Adding type of scheduler to be used, to be picked from a config file, along with it's configurable parameters.
  * Write test code for each scheduler (This should be after the design change)
- * Some of the constants in constants/constants.go can vary based on the environment.  
    Possible to setup the constants at runtime based on the environment?
  * Log fix for declining offer -- different reason when insufficient resources as compared to when there are no
     longer any tasks to schedule.
@@ -18,6 +17,8 @@ To Do:
  * Make def.Task an interface for further modularization and flexibility.
  * Convert def#WattsToConsider(...) to be a receiver of def.Task and change the name of it to Watts(...).
  * Have a generic sorter for task resources instead of having one for each kind of resource.
+ * Handle powerclass not configured on a node condition. As of now, an assumption is made that the powerclass is configured
+   for all the nodes.
 
 **Requires [Performance Co-Pilot](http://pcp.io/) tool pmdumptext to be installed on the
 machine on which electron is launched for logging to work and PCP collector agents installed
@@ -28,9 +29,9 @@ How to run (Use the --help option to get information about other command-line op
 
 `./electron -workload <workload json>`
 
-To run electron with ignoreWatts, run the following command,
+To run electron with Watts as Resource, run the following command,
 
-`./electron -workload <workload json> -ignoreWatts`
+`./electron -workload <workload json> -wattsAsAResource`
 
 
 Workload schema:
@@ -41,30 +42,31 @@ Workload schema:
       "name": "minife",
       "cpu": 3.0,
       "ram": 4096,
-      "watts": 50,
-      "image": "gouravr/minife:v5",
-      "cmd": "cd src && mpirun -np 1 miniFE.x -nx 100 -ny 100 -nz 100",
-      "inst": 9,
-      "class_to_watts" : {
-          "A": 30.2475289996,
-          "B": 35.6491229228,
-          "C": 24.0476734352
-       }
-
+      "watts": 63.141,
+      "class_to_watts": {
+        "A": 93.062,
+        "B": 65.552,
+        "C": 57.897,
+        "D": 60.729
+      },
+      "image": "rdelvalle/minife:electron1",
+      "cmd": "cd src && mpirun -np 3 miniFE.x -nx 100 -ny 100 -nz 100",
+      "inst": 10
    },
    {
       "name": "dgemm",
       "cpu": 3.0,
-      "ram": 4096,
-      "watts": 50,
-      "image": "gouravr/dgemm:v2",
+      "ram": 32,
+      "watts": 85.903,
+      "class_to_watts": {
+        "A": 114.789,
+        "B": 89.133,
+        "C": 82.672,
+        "D": 81.944
+      },
+      "image": "rdelvalle/dgemm:electron1",
       "cmd": "/./mt-dgemm 1024",
-      "inst": 9,
-      "class_to_watts" : {
-          "A": 35.2475289996,
-          "B": 25.6491229228,
-          "C": 29.0476734352
-       }
+      "inst": 10
    }
 ]
 ```

constants/constants.go

@@ -7,34 +7,14 @@ TODO: Clean this up and use Mesos Attributes instead.
 */
 package constants
 
-var Hosts = []string{"stratos-001.cs.binghamton.edu", "stratos-002.cs.binghamton.edu",
-	"stratos-003.cs.binghamton.edu", "stratos-004.cs.binghamton.edu",
-	"stratos-005.cs.binghamton.edu", "stratos-006.cs.binghamton.edu",
-	"stratos-007.cs.binghamton.edu", "stratos-008.cs.binghamton.edu"}
+var Hosts = make(map[string]struct{})
 
 /*
  Classification of the nodes in the cluster based on their Thermal Design Power (TDP).
  The power classes are labelled in the decreasing order of the corresponding TDP, with class A nodes
  	having the highest TDP and class C nodes having the lowest TDP.
 */
-var PowerClasses = map[string]map[string]bool{
-	"A": map[string]bool{
-		"stratos-005.cs.binghamton.edu": true,
-		"stratos-006.cs.binghamton.edu": true,
-	},
-	"B": map[string]bool{
-		"stratos-007.cs.binghamton.edu": true,
-	},
-	"C": map[string]bool{
-		"stratos-008.cs.binghamton.edu": true,
-	},
-	"D": map[string]bool {
-		"stratos-001.cs.binghamton.edu": true,
-		"stratos-002.cs.binghamton.edu": true,
-		"stratos-003.cs.binghamton.edu": true,
-		"stratos-004.cs.binghamton.edu": true,
-	},
-}
+var PowerClasses = make(map[string]map[string]struct{})
 
 /*
   Margin with respect to the required power for a job.

def/task.go

@@ -43,7 +43,7 @@ func TasksFromJSON(uri string) ([]Task, error) {
 func (tsk *Task) UpdateHost(newHost string) bool {
 	// Validation
 	isCorrectHost := false
-	for _, existingHost := range constants.Hosts {
+	for existingHost, _ := range constants.Hosts {
 		if newHost == existingHost {
 			isCorrectHost = true
 		}

pcp/logAndProgressiveExtrema.go

@@ -3,6 +3,7 @@ package pcp
 import (
 	"bitbucket.org/sunybingcloud/electron/constants"
 	"bitbucket.org/sunybingcloud/electron/rapl"
+	"bitbucket.org/sunybingcloud/electron/utilities"
 	"bufio"
 	"container/ring"
 	"log"
@@ -14,7 +15,6 @@ import (
 	"strings"
 	"syscall"
 	"time"
-	"bitbucket.org/sunybingcloud/electron/utilities"
 )
 
 func round(num float64) int {
@@ -202,7 +202,7 @@ func StartPCPLogAndProgressiveExtremaCap(quit chan struct{}, logging *bool, pref
 								// If cannot find any victim, then all nodes have been capped to the maximum and we stop capping at this point.
 							}
 						}
-						if (!canCapAlreadyCappedVictim) {
+						if !canCapAlreadyCappedVictim {
 							log.Println("No Victim left to cap.")
 						}
 					}

pcp/pcp.go

@@ -37,15 +37,6 @@ func Start(quit chan struct{}, logging *bool, prefix string) {
 		// Write to logfile
 		logFile.WriteString(scanner.Text() + "\n")
 
-		/*
-			headers := strings.Split(scanner.Text(), ",")
-
-			for _, hostMetric := range headers {
-				split := strings.Split(hostMetric, ":")
-				fmt.Printf("Host %s: Metric: %s\n", split[0], split[1])
-			}
-		*/
-
 		// Throw away first set of results
 		scanner.Scan()
 
@@ -57,15 +48,7 @@ func Start(quit chan struct{}, logging *bool, prefix string) {
 				logFile.WriteString(scanner.Text() + "\n")
 			}
 
-			/*
-				fmt.Printf("Second: %d\n", seconds)
-				for i, val := range strings.Split(scanner.Text(), ",") {
-					fmt.Printf("host metric: %s val: %s\n", headers[i], val)
-				}*/
-
 			seconds++
-
-			// fmt.Println("--------------------------------")
 		}
 	}(logging)
 

powerCapping/proactiveclusterwidecappers.go

@@ -110,7 +110,7 @@ func (capper ClusterwideCapper) CleverRecap(totalPower map[string]float64,
 	wattsUsages := make(map[string][]float64)
 	hostOfFinishedTask := ""
 	indexOfFinishedTask := -1
-	for _, host := range constants.Hosts {
+	for host, _ := range constants.Hosts {
 		wattsUsages[host] = []float64{0.0}
 	}
 	for host, tasks := range taskMonitor {

scheduler.go

@@ -43,7 +43,7 @@ func main() {
 	}
 
 	if *hiThreshold < *loThreshold {
-		fmt.Println("High threshold is of a lower value than low threhold.")
+		fmt.Println("High threshold is of a lower value than low threshold.")
 		os.Exit(1)
 	}
 
@@ -74,12 +74,12 @@ func main() {
 		return
 	}
 
-	//go pcp.Start(scheduler.PCPLog, &scheduler.RecordPCP, logPrefix)
+	go pcp.Start(scheduler.PCPLog, &scheduler.RecordPCP, logPrefix)
 	//go pcp.StartPCPLogAndExtremaDynamicCap(scheduler.PCPLog, &scheduler.RecordPCP, logPrefix, *hiThreshold, *loThreshold)
-	go pcp.StartPCPLogAndProgressiveExtremaCap(scheduler.PCPLog, &scheduler.RecordPCP, logPrefix, *hiThreshold, *loThreshold)
+	//go pcp.StartPCPLogAndProgressiveExtremaCap(scheduler.PCPLog, &scheduler.RecordPCP, logPrefix, *hiThreshold, *loThreshold)
 	time.Sleep(1 * time.Second) // Take a second between starting PCP log and continuing
 
-	// Attempt to handle signint to not leave pmdumptext running
+	// Attempt to handle SIGINT to not leave pmdumptext running
 	// Catch interrupt
 	go func() {
 		c := make(chan os.Signal, 1)
@@ -120,4 +120,4 @@ func main() {
 		log.Printf("Framework stopped with status %s and error: %s\n", status.String(), err.Error())
 	}
 	log.Println("Exiting...")
-}
+}

schedulers/binPackSortedWattsSortedOffers.go

@@ -127,6 +127,7 @@ func (s *BinPackSortedWattsSortedOffers) ResourceOffers(driver sched.SchedulerDr
 	log.Println("Sorted Offers:")
 	for i := 0; i < len(offers); i++ {
 		offer := offers[i]
+		offerUtils.UpdateEnvironment(offer)
 		offerCPU, _, _ := offerUtils.OfferAgg(offer)
 		log.Printf("Offer[%s].CPU = %f\n", offer.GetHostname(), offerCPU)
 	}

schedulers/binpackedpistoncapping.go

@@ -210,6 +210,7 @@ func (s *BinPackedPistonCapper) ResourceOffers(driver sched.SchedulerDriver, off
 
 	// retrieving the total power for each host in the offers
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		if _, ok := s.totalPower[*offer.Hostname]; !ok {
 			_, _, offerWatts := offerUtils.OfferAgg(offer)
 			s.totalPower[*offer.Hostname] = offerWatts

schedulers/binpacksortedwatts.go

@@ -120,6 +120,7 @@ func (s *BinPackSortedWatts) ResourceOffers(driver sched.SchedulerDriver, offers
 	log.Printf("Received %d resource offers", len(offers))
 
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		select {
 		case <-s.Shutdown:
 			log.Println("Done scheduling tasks: declining offer on [", offer.GetHostname(), "]")

schedulers/bottomHeavy.go

@@ -18,12 +18,12 @@ import (
 )
 
 /*
-Tasks are categorized into small and large tasks based on the watts requirement.
-All the small tasks are packed into offers from agents belonging to power class C and power class D, using BinPacking.
-All the large tasks are spread among the offers from agents belonging to power class A and power class B, using FirstFit.
+Tasks are categorized into small and large tasks based on watts requirements.
+All the large tasks are packed into offers from agents belonging to power classes A and B, using Bin-Packing.
+All the small tasks are spread among offers from agents belonging to power class C and D, using First-Fit.
 
-BinPacking has the most effect when co-scheduling of tasks is increased. Large tasks typically utilize more resources and hence,
-	co-scheduling them has a great impact on the total power utilization.
+Bin-Packing has the most effect when co-scheduling of tasks is increased. Large tasks typically utilize more resources and hence,
+co-scheduling them has a great impact on the total power utilization.
 */
 
 func (s *BottomHeavy) takeOfferBinPack(offer *mesos.Offer, totalCPU, totalRAM, totalWatts,
@@ -159,7 +159,7 @@ func (s *BottomHeavy) createTaskInfoAndLogSchedTrace(offer *mesos.Offer, task de
 	return taskToSchedule
 }
 
-// Using BinPacking to pack small tasks into this offer.
+// Using BinPacking to pack large tasks into the given offers.
 func (s *BottomHeavy) pack(offers []*mesos.Offer, driver sched.SchedulerDriver) {
 	for _, offer := range offers {
 		select {
@@ -221,7 +221,7 @@ func (s *BottomHeavy) pack(offers []*mesos.Offer, driver sched.SchedulerDriver)
 	}
 }
 
-// Using first fit to spread large tasks into these offers.
+// Using First-Fit to spread small tasks among the given offers.
 func (s *BottomHeavy) spread(offers []*mesos.Offer, driver sched.SchedulerDriver) {
 	for _, offer := range offers {
 		select {
@@ -282,6 +282,7 @@ func (s *BottomHeavy) ResourceOffers(driver sched.SchedulerDriver, offers []*mes
 	offersLightPowerClasses := []*mesos.Offer{}
 
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		select {
 		case <-s.Shutdown:
 			log.Println("Done scheduling tasks: declining offer on [", offer.GetHostname(), "]")
@@ -292,13 +293,19 @@ func (s *BottomHeavy) ResourceOffers(driver sched.SchedulerDriver, offers []*mes
 		default:
 		}
 
-		if constants.PowerClasses["A"][*offer.Hostname] ||
-			constants.PowerClasses["B"][*offer.Hostname] {
+		if _, ok := constants.PowerClasses["A"][*offer.Hostname]; ok {
 			offersHeavyPowerClasses = append(offersHeavyPowerClasses, offer)
-		} else if constants.PowerClasses["C"][*offer.Hostname] ||
-			constants.PowerClasses["D"][*offer.Hostname] {
+		}
+		if _, ok := constants.PowerClasses["B"][*offer.Hostname]; ok {
+			offersHeavyPowerClasses = append(offersHeavyPowerClasses, offer)
+		}
+		if _, ok := constants.PowerClasses["C"][*offer.Hostname]; ok {
 			offersLightPowerClasses = append(offersLightPowerClasses, offer)
 		}
+		if _, ok := constants.PowerClasses["D"][*offer.Hostname]; ok {
+			offersLightPowerClasses = append(offersLightPowerClasses, offer)
+		}
+
 	}
 
 	log.Println("Packing Large tasks into ClassAB offers:")

schedulers/bpswMaxMin.go

@@ -164,6 +164,7 @@ func (s *BPSWMaxMinWatts) ResourceOffers(driver sched.SchedulerDriver, offers []
 	log.Printf("Received %d resource offers", len(offers))
 
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		select {
 		case <-s.Shutdown:
 			log.Println("Done scheduling tasks: declining offer on [", offer.GetHostname(), "]")

schedulers/bpswMaxMinPistonCapping.go

@@ -261,6 +261,7 @@ func (s *BPSWMaxMinPistonCapping) ResourceOffers(driver sched.SchedulerDriver, o
 	log.Printf("Received %d resource offers", len(offers))
 
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		select {
 		case <-s.Shutdown:
 			log.Println("Done scheduling tasks: declining offer on [", offer.GetHostname(), "]")

schedulers/bpswMaxMinProacCC.go

@@ -164,7 +164,7 @@ func (s *BPSWMaxMinProacCC) startCapping() {
 						// updating cap value
 						bpMaxMinProacCCCapValue = bpMaxMinProacCCNewCapValue
 						if bpMaxMinProacCCCapValue > 0.0 {
-							for _, host := range constants.Hosts {
+							for host, _ := range constants.Hosts {
 								// Rounding cap value to nearest int
 								if err := rapl.Cap(host, "rapl", float64(int(math.Floor(bpMaxMinProacCCCapValue+0.5)))); err != nil {
 									log.Println(err)
@@ -190,7 +190,7 @@ func (s *BPSWMaxMinProacCC) startRecapping() {
 				bpMaxMinProacCCMutex.Lock()
 				// If stopped performing cluster-wide capping, then we need to recap.
 				if s.isRecapping && bpMaxMinProacCCRecapValue > 0.0 {
-					for _, host := range constants.Hosts {
+					for host, _ := range constants.Hosts {
 						// Rounding the recap value to the nearest int
 						if err := rapl.Cap(host, "rapl", float64(int(math.Floor(bpMaxMinProacCCRecapValue+0.5)))); err != nil {
 							log.Println(err)
@@ -300,6 +300,7 @@ func (s *BPSWMaxMinProacCC) ResourceOffers(driver sched.SchedulerDriver, offers
 
 	// retrieving the available power for all the hosts in the offers.
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		_, _, offerWatts := offerUtils.OfferAgg(offer)
 		s.availablePower[*offer.Hostname] = offerWatts
 		// setting total power if the first time

schedulers/firstfit.go

@@ -119,6 +119,7 @@ func (s *FirstFit) ResourceOffers(driver sched.SchedulerDriver, offers []*mesos.
 	log.Printf("Received %d resource offers", len(offers))
 
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		select {
 		case <-s.Shutdown:
 			log.Println("Done scheduling tasks: declining offer on [", offer.GetHostname(), "]")

schedulers/firstfitProacCC.go

@@ -164,7 +164,7 @@ func (s *FirstFitProacCC) startCapping() {
 				// Need to cap the cluster to the fcfsCurrentCapValue.
 				fcfsMutex.Lock()
 				if fcfsCurrentCapValue > 0.0 {
-					for _, host := range constants.Hosts {
+					for host, _ := range constants.Hosts {
 						// Rounding curreCapValue to the nearest int.
 						if err := rapl.Cap(host, "rapl", float64(int(math.Floor(fcfsCurrentCapValue+0.5)))); err != nil {
 							log.Println(err)
@@ -188,7 +188,7 @@ func (s *FirstFitProacCC) startRecapping() {
 				fcfsMutex.Lock()
 				// If stopped performing cluster wide capping then we need to explicitly cap the entire cluster.
 				if s.isRecapping && fcfsRecapValue > 0.0 {
-					for _, host := range constants.Hosts {
+					for host, _ := range constants.Hosts {
 						// Rounding curreCapValue to the nearest int.
 						if err := rapl.Cap(host, "rapl", float64(int(math.Floor(fcfsRecapValue+0.5)))); err != nil {
 							log.Println(err)
@@ -233,6 +233,7 @@ func (s *FirstFitProacCC) ResourceOffers(driver sched.SchedulerDriver, offers []
 
 	// retrieving the available power for all the hosts in the offers.
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		_, _, offer_watts := offerUtils.OfferAgg(offer)
 		s.availablePower[*offer.Hostname] = offer_watts
 		// setting total power if the first time.

schedulers/firstfitSortedOffers.go

@@ -126,6 +126,7 @@ func (s *FirstFitSortedOffers) ResourceOffers(driver sched.SchedulerDriver, offe
 	log.Println("Sorted Offers:")
 	for i := 0; i < len(offers); i++ {
 		offer := offers[i]
+		offerUtils.UpdateEnvironment(offer)
 		offerCPU, _, _ := offerUtils.OfferAgg(offer)
 		log.Printf("Offer[%s].CPU = %f\n", offer.GetHostname(), offerCPU)
 	}

schedulers/firstfitSortedWattsProacCC.go

@@ -177,7 +177,7 @@ func (s *FirstFitSortedWattsProacCC) startCapping() {
 				// Need to cap the cluster to the rankedCurrentCapValue.
 				rankedMutex.Lock()
 				if rankedCurrentCapValue > 0.0 {
-					for _, host := range constants.Hosts {
+					for host, _ := range constants.Hosts {
 						// Rounding currentCapValue to the nearest int.
 						if err := rapl.Cap(host, "rapl", float64(int(math.Floor(rankedCurrentCapValue+0.5)))); err != nil {
 							log.Println(err)
@@ -201,7 +201,7 @@ func (s *FirstFitSortedWattsProacCC) startRecapping() {
 				rankedMutex.Lock()
 				// If stopped performing cluster wide capping then we need to explicitly cap the entire cluster.
 				if s.isRecapping && rankedRecapValue > 0.0 {
-					for _, host := range constants.Hosts {
+					for host, _ := range constants.Hosts {
 						// Rounding currentCapValue to the nearest int.
 						if err := rapl.Cap(host, "rapl", float64(int(math.Floor(rankedRecapValue+0.5)))); err != nil {
 							log.Println(err)
@@ -246,6 +246,7 @@ func (s *FirstFitSortedWattsProacCC) ResourceOffers(driver sched.SchedulerDriver
 
 	// retrieving the available power for all the hosts in the offers.
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		_, _, offer_watts := offerUtils.OfferAgg(offer)
 		s.availablePower[*offer.Hostname] = offer_watts
 		// setting total power if the first time.

schedulers/firstfitSortedWattsSortedOffers.go

@@ -128,6 +128,7 @@ func (s *FirstFitSortedWattsSortedOffers) ResourceOffers(driver sched.SchedulerD
 	log.Println("Sorted Offers:")
 	for i := 0; i < len(offers); i++ {
 		offer := offers[i]
+		offerUtils.UpdateEnvironment(offer)
 		offerCPU, _, _ := offerUtils.OfferAgg(offer)
 		log.Printf("Offer[%s].CPU = %f\n", offer.GetHostname(), offerCPU)
 	}

schedulers/firstfitsortedwatts.go

@@ -122,6 +122,7 @@ func (s *FirstFitSortedWatts) ResourceOffers(driver sched.SchedulerDriver, offer
 	log.Printf("Received %d resource offers", len(offers))
 
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		select {
 		case <-s.Shutdown:
 			log.Println("Done scheduling tasks: declining offer on [", offer.GetHostname(), "]")

schedulers/firstfitwattsonly.go

@@ -112,6 +112,7 @@ func (s *FirstFitWattsOnly) ResourceOffers(driver sched.SchedulerDriver, offers
 	log.Printf("Received %d resource offers", len(offers))
 
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		select {
 		case <-s.Shutdown:
 			log.Println("Done scheduling tasks: declining offer on [", offer.GetHostname(), "]")

schedulers/helpers.go

@@ -18,7 +18,7 @@ func coLocated(tasks map[string]bool) {
 // Get the powerClass of the given hostname
 func hostToPowerClass(hostName string) string {
 	for powerClass, hosts := range constants.PowerClasses {
-		if ok := hosts[hostName]; ok {
+		if _, ok := hosts[hostName]; ok {
 			return powerClass
 		}
 	}

schedulers/topHeavy.go

@@ -19,8 +19,8 @@ import (
 
 /*
 Tasks are categorized into small and large tasks based on the watts requirement.
-All the large tasks are packed into offers from agents belonging to power class A and power class B, using BinPacking.
-All the small tasks are spread among the offers from agents belonging to power class C and power class D, using FirstFit.
+All the small tasks are packed into offers from agents belonging to power class C and power class D, using BinPacking.
+All the large tasks are spread among the offers from agents belonging to power class A and power class B, using FirstFit.
 
 This was done to give a little more room for the large tasks (power intensive) for execution and reduce the possibility of
 starvation of power intensive tasks.
@@ -281,6 +281,7 @@ func (s *TopHeavy) ResourceOffers(driver sched.SchedulerDriver, offers []*mesos.
 	offersLightPowerClasses := []*mesos.Offer{}
 
 	for _, offer := range offers {
+		offerUtils.UpdateEnvironment(offer)
 		select {
 		case <-s.Shutdown:
 			log.Println("Done scheduling tasks: declining offer on [", offer.GetHostname(), "]")
@@ -291,11 +292,16 @@ func (s *TopHeavy) ResourceOffers(driver sched.SchedulerDriver, offers []*mesos.
 		default:
 		}
 
-		if constants.PowerClasses["A"][*offer.Hostname] ||
-			constants.PowerClasses["B"][*offer.Hostname] {
+		if _, ok := constants.PowerClasses["A"][*offer.Hostname]; ok {
 			offersHeavyPowerClasses = append(offersHeavyPowerClasses, offer)
-		} else if constants.PowerClasses["C"][*offer.Hostname] ||
-			constants.PowerClasses["D"][*offer.Hostname] {
+		}
+		if _, ok := constants.PowerClasses["B"][*offer.Hostname]; ok {
+			offersHeavyPowerClasses = append(offersHeavyPowerClasses, offer)
+		}
+		if _, ok := constants.PowerClasses["C"][*offer.Hostname]; ok {
+			offersLightPowerClasses = append(offersLightPowerClasses, offer)
+		}
+		if _, ok := constants.PowerClasses["D"][*offer.Hostname]; ok {
 			offersLightPowerClasses = append(offersLightPowerClasses, offer)
 		}
 	}

utilities/offerUtils/offerUtils.go

@@ -1,7 +1,10 @@
 package offerUtils
 
 import (
+	"bitbucket.org/sunybingcloud/electron-archive/utilities/offerUtils"
+	"bitbucket.org/sunybingcloud/electron/constants"
 	mesos "github.com/mesos/mesos-go/mesosproto"
+	"log"
 	"strings"
 )
 
@@ -60,3 +63,26 @@ func HostMismatch(offerHost string, taskHost string) bool {
 	}
 	return false
 }
+
+// If the host in the offer is a new host, add the host to the set of Hosts and
+// register the powerclass of this host.
+func UpdateEnvironment(offer *mesos.Offer) {
+	var host = offer.GetHostname()
+	// If this host is not present in the set of hosts.
+	if _, ok := constants.Hosts[host]; !ok {
+		log.Printf("New host detected. Adding host [%s]", host)
+		// Add this host.
+		constants.Hosts[host] = struct{}{}
+		// Get the power class of this host.
+		class := offerUtils.PowerClass(offer)
+		log.Printf("Registering the power class... Host [%s] --> PowerClass [%s]", host, class)
+		// If new power class, register the power class.
+		if _, ok := constants.PowerClasses[class]; !ok {
+			constants.PowerClasses[class] = make(map[string]struct{})
+		}
+		// If the host of this class is not yet present in PowerClasses[class], add it.
+		if _, ok := constants.PowerClasses[class][host]; !ok {
+			constants.PowerClasses[class][host] = struct{}{}
+		}
+	}
+}