vendor/k8s.io/kubernetes/pkg/controller/podautoscaler/replica_calculator.go - cloudstack-kubernetes-provider - Git at Google

 /*
 Copyright 2016 The Kubernetes Authors.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

 package podautoscaler

 import (
 	"fmt"
 	"math"
 	"time"

 	autoscaling "k8s.io/api/autoscaling/v2beta2"
 	"k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/util/sets"
 	corelisters "k8s.io/client-go/listers/core/v1"
 	podutil "k8s.io/kubernetes/pkg/api/v1/pod"
 	metricsclient "k8s.io/kubernetes/pkg/controller/podautoscaler/metrics"
 )

 const (
 	// defaultTestingTolerance is default value for calculating when to
 	// scale up/scale down.
 	defaultTestingTolerance                     = 0.1
 	defaultTestingCpuInitializationPeriod       = 2 * time.Minute
 	defaultTestingDelayOfInitialReadinessStatus = 10 * time.Second
 )

 type ReplicaCalculator struct {
 	metricsClient                 metricsclient.MetricsClient
 	podLister                     corelisters.PodLister
 	tolerance                     float64
 	cpuInitializationPeriod       time.Duration
 	delayOfInitialReadinessStatus time.Duration
 }

 func NewReplicaCalculator(metricsClient metricsclient.MetricsClient, podLister corelisters.PodLister, tolerance float64, cpuInitializationPeriod, delayOfInitialReadinessStatus time.Duration) *ReplicaCalculator {
 	return &ReplicaCalculator{
 		metricsClient:                 metricsClient,
 		podLister:                     podLister,
 		tolerance:                     tolerance,
 		cpuInitializationPeriod:       cpuInitializationPeriod,
 		delayOfInitialReadinessStatus: delayOfInitialReadinessStatus,
 	}
 }

 // GetResourceReplicas calculates the desired replica count based on a target resource utilization percentage
 // of the given resource for pods matching the given selector in the given namespace, and the current replica count
 func (c *ReplicaCalculator) GetResourceReplicas(currentReplicas int32, targetUtilization int32, resource v1.ResourceName, namespace string, selector labels.Selector) (replicaCount int32, utilization int32, rawUtilization int64, timestamp time.Time, err error) {
 	metrics, timestamp, err := c.metricsClient.GetResourceMetric(resource, namespace, selector)
 	if err != nil {
 		return 0, 0, 0, time.Time{}, fmt.Errorf("unable to get metrics for resource %s: %v", resource, err)
 	}
 	podList, err := c.podLister.Pods(namespace).List(selector)
 	if err != nil {
 		return 0, 0, 0, time.Time{}, fmt.Errorf("unable to get pods while calculating replica count: %v", err)
 	}

 	itemsLen := len(podList)
 	if itemsLen == 0 {
 		return 0, 0, 0, time.Time{}, fmt.Errorf("no pods returned by selector while calculating replica count")
 	}

 	readyPodCount, ignoredPods, missingPods := groupPods(podList, metrics, resource, c.cpuInitializationPeriod, c.delayOfInitialReadinessStatus)
 	removeMetricsForPods(metrics, ignoredPods)
 	requests, err := calculatePodRequests(podList, resource)
 	if err != nil {
 		return 0, 0, 0, time.Time{}, err
 	}

 	if len(metrics) == 0 {
 		return 0, 0, 0, time.Time{}, fmt.Errorf("did not receive metrics for any ready pods")
 	}

 	usageRatio, utilization, rawUtilization, err := metricsclient.GetResourceUtilizationRatio(metrics, requests, targetUtilization)
 	if err != nil {
 		return 0, 0, 0, time.Time{}, err
 	}

 	rebalanceIgnored := len(ignoredPods) > 0 && usageRatio > 1.0
 	if !rebalanceIgnored && len(missingPods) == 0 {
 		if math.Abs(1.0-usageRatio) <= c.tolerance {
 			// return the current replicas if the change would be too small
 			return currentReplicas, utilization, rawUtilization, timestamp, nil
 		}

 		// if we don't have any unready or missing pods, we can calculate the new replica count now
 		return int32(math.Ceil(usageRatio * float64(readyPodCount))), utilization, rawUtilization, timestamp, nil
 	}

 	if len(missingPods) > 0 {
 		if usageRatio < 1.0 {
 			// on a scale-down, treat missing pods as using 100% of the resource request
 			for podName := range missingPods {
 				metrics[podName] = metricsclient.PodMetric{Value: requests[podName]}
 			}
 		} else if usageRatio > 1.0 {
 			// on a scale-up, treat missing pods as using 0% of the resource request
 			for podName := range missingPods {
 				metrics[podName] = metricsclient.PodMetric{Value: 0}
 			}
 		}
 	}

 	if rebalanceIgnored {
 		// on a scale-up, treat unready pods as using 0% of the resource request
 		for podName := range ignoredPods {
 			metrics[podName] = metricsclient.PodMetric{Value: 0}
 		}
 	}

 	// re-run the utilization calculation with our new numbers
 	newUsageRatio, _, _, err := metricsclient.GetResourceUtilizationRatio(metrics, requests, targetUtilization)
 	if err != nil {
 		return 0, utilization, rawUtilization, time.Time{}, err
 	}

 	if math.Abs(1.0-newUsageRatio) <= c.tolerance || (usageRatio < 1.0 && newUsageRatio > 1.0) || (usageRatio > 1.0 && newUsageRatio < 1.0) {
 		// return the current replicas if the change would be too small,
 		// or if the new usage ratio would cause a change in scale direction
 		return currentReplicas, utilization, rawUtilization, timestamp, nil
 	}

 	// return the result, where the number of replicas considered is
 	// however many replicas factored into our calculation
 	return int32(math.Ceil(newUsageRatio * float64(len(metrics)))), utilization, rawUtilization, timestamp, nil
 }

 // GetRawResourceReplicas calculates the desired replica count based on a target resource utilization (as a raw milli-value)
 // for pods matching the given selector in the given namespace, and the current replica count
 func (c *ReplicaCalculator) GetRawResourceReplicas(currentReplicas int32, targetUtilization int64, resource v1.ResourceName, namespace string, selector labels.Selector) (replicaCount int32, utilization int64, timestamp time.Time, err error) {
 	metrics, timestamp, err := c.metricsClient.GetResourceMetric(resource, namespace, selector)
 	if err != nil {
 		return 0, 0, time.Time{}, fmt.Errorf("unable to get metrics for resource %s: %v", resource, err)
 	}

 	replicaCount, utilization, err = c.calcPlainMetricReplicas(metrics, currentReplicas, targetUtilization, namespace, selector, resource)
 	return replicaCount, utilization, timestamp, err
 }

 // GetMetricReplicas calculates the desired replica count based on a target metric utilization
 // (as a milli-value) for pods matching the given selector in the given namespace, and the
 // current replica count
 func (c *ReplicaCalculator) GetMetricReplicas(currentReplicas int32, targetUtilization int64, metricName string, namespace string, selector labels.Selector, metricSelector labels.Selector) (replicaCount int32, utilization int64, timestamp time.Time, err error) {
 	metrics, timestamp, err := c.metricsClient.GetRawMetric(metricName, namespace, selector, metricSelector)
 	if err != nil {
 		return 0, 0, time.Time{}, fmt.Errorf("unable to get metric %s: %v", metricName, err)
 	}

 	replicaCount, utilization, err = c.calcPlainMetricReplicas(metrics, currentReplicas, targetUtilization, namespace, selector, v1.ResourceName(""))
 	return replicaCount, utilization, timestamp, err
 }

 // calcPlainMetricReplicas calculates the desired replicas for plain (i.e. non-utilization percentage) metrics.
 func (c *ReplicaCalculator) calcPlainMetricReplicas(metrics metricsclient.PodMetricsInfo, currentReplicas int32, targetUtilization int64, namespace string, selector labels.Selector, resource v1.ResourceName) (replicaCount int32, utilization int64, err error) {

 	podList, err := c.podLister.Pods(namespace).List(selector)
 	if err != nil {
 		return 0, 0, fmt.Errorf("unable to get pods while calculating replica count: %v", err)
 	}

 	if len(podList) == 0 {
 		return 0, 0, fmt.Errorf("no pods returned by selector while calculating replica count")
 	}

 	readyPodCount, ignoredPods, missingPods := groupPods(podList, metrics, resource, c.cpuInitializationPeriod, c.delayOfInitialReadinessStatus)
 	removeMetricsForPods(metrics, ignoredPods)

 	if len(metrics) == 0 {
 		return 0, 0, fmt.Errorf("did not receive metrics for any ready pods")
 	}

 	usageRatio, utilization := metricsclient.GetMetricUtilizationRatio(metrics, targetUtilization)

 	rebalanceIgnored := len(ignoredPods) > 0 && usageRatio > 1.0

 	if !rebalanceIgnored && len(missingPods) == 0 {
 		if math.Abs(1.0-usageRatio) <= c.tolerance {
 			// return the current replicas if the change would be too small
 			return currentReplicas, utilization, nil
 		}

 		// if we don't have any unready or missing pods, we can calculate the new replica count now
 		return int32(math.Ceil(usageRatio * float64(readyPodCount))), utilization, nil
 	}

 	if len(missingPods) > 0 {
 		if usageRatio < 1.0 {
 			// on a scale-down, treat missing pods as using 100% of the resource request
 			for podName := range missingPods {
 				metrics[podName] = metricsclient.PodMetric{Value: targetUtilization}
 			}
 		} else {
 			// on a scale-up, treat missing pods as using 0% of the resource request
 			for podName := range missingPods {
 				metrics[podName] = metricsclient.PodMetric{Value: 0}
 			}
 		}
 	}

 	if rebalanceIgnored {
 		// on a scale-up, treat unready pods as using 0% of the resource request
 		for podName := range ignoredPods {
 			metrics[podName] = metricsclient.PodMetric{Value: 0}
 		}
 	}

 	// re-run the utilization calculation with our new numbers
 	newUsageRatio, _ := metricsclient.GetMetricUtilizationRatio(metrics, targetUtilization)

 	if math.Abs(1.0-newUsageRatio) <= c.tolerance || (usageRatio < 1.0 && newUsageRatio > 1.0) || (usageRatio > 1.0 && newUsageRatio < 1.0) {
 		// return the current replicas if the change would be too small,
 		// or if the new usage ratio would cause a change in scale direction
 		return currentReplicas, utilization, nil
 	}

 	// return the result, where the number of replicas considered is
 	// however many replicas factored into our calculation
 	return int32(math.Ceil(newUsageRatio * float64(len(metrics)))), utilization, nil
 }

 // GetObjectMetricReplicas calculates the desired replica count based on a target metric utilization (as a milli-value)
 // for the given object in the given namespace, and the current replica count.
 func (c *ReplicaCalculator) GetObjectMetricReplicas(currentReplicas int32, targetUtilization int64, metricName string, namespace string, objectRef *autoscaling.CrossVersionObjectReference, selector labels.Selector, metricSelector labels.Selector) (replicaCount int32, utilization int64, timestamp time.Time, err error) {
 	utilization, timestamp, err = c.metricsClient.GetObjectMetric(metricName, namespace, objectRef, metricSelector)
 	if err != nil {
 		return 0, 0, time.Time{}, fmt.Errorf("unable to get metric %s: %v on %s %s/%s", metricName, objectRef.Kind, namespace, objectRef.Name, err)
 	}

 	usageRatio := float64(utilization) / float64(targetUtilization)
 	if math.Abs(1.0-usageRatio) <= c.tolerance {
 		// return the current replicas if the change would be too small
 		return currentReplicas, utilization, timestamp, nil
 	}

 	readyPodCount, err := c.getReadyPodsCount(namespace, selector)

 	if err != nil {
 		return 0, 0, time.Time{}, fmt.Errorf("unable to calculate ready pods: %s", err)
 	}

 	replicaCount = int32(math.Ceil(usageRatio * float64(readyPodCount)))

 	return replicaCount, utilization, timestamp, nil
 }

 // @TODO(mattjmcnaughton) Many different functions in this module use variations
 // of this function. Make this function generic, so we don't repeat the same
 // logic in multiple places.
 func (c *ReplicaCalculator) getReadyPodsCount(namespace string, selector labels.Selector) (int64, error) {
 	podList, err := c.podLister.Pods(namespace).List(selector)
 	if err != nil {
 		return 0, fmt.Errorf("unable to get pods while calculating replica count: %v", err)
 	}

 	if len(podList) == 0 {
 		return 0, fmt.Errorf("no pods returned by selector while calculating replica count")
 	}

 	readyPodCount := 0

 	for _, pod := range podList {
 		if pod.Status.Phase == v1.PodRunning && podutil.IsPodReady(pod) {
 			readyPodCount++
 		}
 	}

 	return int64(readyPodCount), nil
 }

 // GetExternalMetricReplicas calculates the desired replica count based on a
 // target metric value (as a milli-value) for the external metric in the given
 // namespace, and the current replica count.
 func (c *ReplicaCalculator) GetExternalMetricReplicas(currentReplicas int32, targetUtilization int64, metricName, namespace string, metricSelector *metav1.LabelSelector, podSelector labels.Selector) (replicaCount int32, utilization int64, timestamp time.Time, err error) {
 	metricLabelSelector, err := metav1.LabelSelectorAsSelector(metricSelector)
 	if err != nil {
 		return 0, 0, time.Time{}, err
 	}
 	metrics, timestamp, err := c.metricsClient.GetExternalMetric(metricName, namespace, metricLabelSelector)
 	if err != nil {
 		return 0, 0, time.Time{}, fmt.Errorf("unable to get external metric %s/%s/%+v: %s", namespace, metricName, metricSelector, err)
 	}
 	utilization = 0
 	for _, val := range metrics {
 		utilization = utilization + val
 	}

 	readyPodCount, err := c.getReadyPodsCount(namespace, podSelector)

 	if err != nil {
 		return 0, 0, time.Time{}, fmt.Errorf("unable to calculate ready pods: %s", err)
 	}

 	usageRatio := float64(utilization) / float64(targetUtilization)
 	if math.Abs(1.0-usageRatio) <= c.tolerance {
 		// return the current replicas if the change would be too small
 		return currentReplicas, utilization, timestamp, nil
 	}

 	return int32(math.Ceil(usageRatio * float64(readyPodCount))), utilization, timestamp, nil
 }

 // GetExternalPerPodMetricReplicas calculates the desired replica count based on a
 // target metric value per pod (as a milli-value) for the external metric in the
 // given namespace, and the current replica count.
 func (c *ReplicaCalculator) GetExternalPerPodMetricReplicas(currentReplicas int32, targetUtilizationPerPod int64, metricName, namespace string, metricSelector *metav1.LabelSelector) (replicaCount int32, utilization int64, timestamp time.Time, err error) {
 	metricLabelSelector, err := metav1.LabelSelectorAsSelector(metricSelector)
 	if err != nil {
 		return 0, 0, time.Time{}, err
 	}
 	metrics, timestamp, err := c.metricsClient.GetExternalMetric(metricName, namespace, metricLabelSelector)
 	if err != nil {
 		return 0, 0, time.Time{}, fmt.Errorf("unable to get external metric %s/%s/%+v: %s", namespace, metricName, metricSelector, err)
 	}
 	utilization = 0
 	for _, val := range metrics {
 		utilization = utilization + val
 	}

 	replicaCount = currentReplicas
 	usageRatio := float64(utilization) / (float64(targetUtilizationPerPod) * float64(replicaCount))
 	if math.Abs(1.0-usageRatio) > c.tolerance {
 		// update number of replicas if the change is large enough
 		replicaCount = int32(math.Ceil(float64(utilization) / float64(targetUtilizationPerPod)))
 	}
 	utilization = int64(math.Ceil(float64(utilization) / float64(currentReplicas)))
 	return replicaCount, utilization, timestamp, nil
 }

 func groupPods(pods []*v1.Pod, metrics metricsclient.PodMetricsInfo, resource v1.ResourceName, cpuInitializationPeriod, delayOfInitialReadinessStatus time.Duration) (readyPodCount int, ignoredPods sets.String, missingPods sets.String) {
 	missingPods = sets.NewString()
 	ignoredPods = sets.NewString()
 	for _, pod := range pods {
 		if pod.DeletionTimestamp != nil || pod.Status.Phase == v1.PodFailed {
 			continue
 		}
 		metric, found := metrics[pod.Name]
 		if !found {
 			missingPods.Insert(pod.Name)
 			continue
 		}
 		if resource == v1.ResourceCPU {
 			var ignorePod bool
 			_, condition := podutil.GetPodCondition(&pod.Status, v1.PodReady)
 			if condition == nil || pod.Status.StartTime == nil {
 				ignorePod = true
 			} else {
 				// Pod still within possible initialisation period.
 				if pod.Status.StartTime.Add(cpuInitializationPeriod).After(time.Now()) {
 					// Ignore sample if pod is unready or one window of metric wasn't collected since last state transition.
 					ignorePod = condition.Status == v1.ConditionFalse || metric.Timestamp.Before(condition.LastTransitionTime.Time.Add(metric.Window))
 				} else {
 					// Ignore metric if pod is unready and it has never been ready.
 					ignorePod = condition.Status == v1.ConditionFalse && pod.Status.StartTime.Add(delayOfInitialReadinessStatus).After(condition.LastTransitionTime.Time)
 				}
 			}
 			if ignorePod {
 				ignoredPods.Insert(pod.Name)
 				continue
 			}
 		}
 		readyPodCount++
 	}
 	return
 }

 func calculatePodRequests(pods []*v1.Pod, resource v1.ResourceName) (map[string]int64, error) {
 	requests := make(map[string]int64, len(pods))
 	for _, pod := range pods {
 		podSum := int64(0)
 		for _, container := range pod.Spec.Containers {
 			if containerRequest, ok := container.Resources.Requests[resource]; ok {
 				podSum += containerRequest.MilliValue()
 			} else {
 				return nil, fmt.Errorf("missing request for %s", resource)
 			}
 		}
 		requests[pod.Name] = podSum
 	}
 	return requests, nil
 }

 func removeMetricsForPods(metrics metricsclient.PodMetricsInfo, pods sets.String) {
 	for _, pod := range pods.UnsortedList() {
 		delete(metrics, pod)
 	}
 }
	/*
	Copyright 2016 The Kubernetes Authors.

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	*/

	package podautoscaler

	import (
	"fmt"
	"math"
	"time"

	autoscaling "k8s.io/api/autoscaling/v2beta2"
	"k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/util/sets"
	corelisters "k8s.io/client-go/listers/core/v1"
	podutil "k8s.io/kubernetes/pkg/api/v1/pod"
	metricsclient "k8s.io/kubernetes/pkg/controller/podautoscaler/metrics"
	)

	const (
	// defaultTestingTolerance is default value for calculating when to
	// scale up/scale down.
	defaultTestingTolerance = 0.1
	defaultTestingCpuInitializationPeriod = 2 * time.Minute
	defaultTestingDelayOfInitialReadinessStatus = 10 * time.Second
	)

	type ReplicaCalculator struct {
	metricsClient metricsclient.MetricsClient
	podLister corelisters.PodLister
	tolerance float64
	cpuInitializationPeriod time.Duration
	delayOfInitialReadinessStatus time.Duration
	}

	func NewReplicaCalculator(metricsClient metricsclient.MetricsClient, podLister corelisters.PodLister, tolerance float64, cpuInitializationPeriod, delayOfInitialReadinessStatus time.Duration) *ReplicaCalculator {
	return &ReplicaCalculator{
	metricsClient: metricsClient,
	podLister: podLister,
	tolerance: tolerance,
	cpuInitializationPeriod: cpuInitializationPeriod,
	delayOfInitialReadinessStatus: delayOfInitialReadinessStatus,
	}
	}

	// GetResourceReplicas calculates the desired replica count based on a target resource utilization percentage
	// of the given resource for pods matching the given selector in the given namespace, and the current replica count
	func (c *ReplicaCalculator) GetResourceReplicas(currentReplicas int32, targetUtilization int32, resource v1.ResourceName, namespace string, selector labels.Selector) (replicaCount int32, utilization int32, rawUtilization int64, timestamp time.Time, err error) {
	metrics, timestamp, err := c.metricsClient.GetResourceMetric(resource, namespace, selector)
	if err != nil {
	return 0, 0, 0, time.Time{}, fmt.Errorf("unable to get metrics for resource %s: %v", resource, err)
	}
	podList, err := c.podLister.Pods(namespace).List(selector)
	if err != nil {
	return 0, 0, 0, time.Time{}, fmt.Errorf("unable to get pods while calculating replica count: %v", err)
	}

	itemsLen := len(podList)
	if itemsLen == 0 {
	return 0, 0, 0, time.Time{}, fmt.Errorf("no pods returned by selector while calculating replica count")
	}

	readyPodCount, ignoredPods, missingPods := groupPods(podList, metrics, resource, c.cpuInitializationPeriod, c.delayOfInitialReadinessStatus)
	removeMetricsForPods(metrics, ignoredPods)
	requests, err := calculatePodRequests(podList, resource)
	if err != nil {
	return 0, 0, 0, time.Time{}, err
	}

	if len(metrics) == 0 {
	return 0, 0, 0, time.Time{}, fmt.Errorf("did not receive metrics for any ready pods")
	}

	usageRatio, utilization, rawUtilization, err := metricsclient.GetResourceUtilizationRatio(metrics, requests, targetUtilization)
	if err != nil {
	return 0, 0, 0, time.Time{}, err
	}

	rebalanceIgnored := len(ignoredPods) > 0 && usageRatio > 1.0
	if !rebalanceIgnored && len(missingPods) == 0 {
	if math.Abs(1.0-usageRatio) <= c.tolerance {
	// return the current replicas if the change would be too small
	return currentReplicas, utilization, rawUtilization, timestamp, nil
	}

	// if we don't have any unready or missing pods, we can calculate the new replica count now
	return int32(math.Ceil(usageRatio * float64(readyPodCount))), utilization, rawUtilization, timestamp, nil
	}

	if len(missingPods) > 0 {
	if usageRatio < 1.0 {
	// on a scale-down, treat missing pods as using 100% of the resource request
	for podName := range missingPods {
	metrics[podName] = metricsclient.PodMetric{Value: requests[podName]}
	}
	} else if usageRatio > 1.0 {
	// on a scale-up, treat missing pods as using 0% of the resource request
	for podName := range missingPods {
	metrics[podName] = metricsclient.PodMetric{Value: 0}
	}
	}
	}

	if rebalanceIgnored {
	// on a scale-up, treat unready pods as using 0% of the resource request
	for podName := range ignoredPods {
	metrics[podName] = metricsclient.PodMetric{Value: 0}
	}
	}

	// re-run the utilization calculation with our new numbers
	newUsageRatio, _, _, err := metricsclient.GetResourceUtilizationRatio(metrics, requests, targetUtilization)
	if err != nil {
	return 0, utilization, rawUtilization, time.Time{}, err
	}

	if math.Abs(1.0-newUsageRatio) <= c.tolerance \|\| (usageRatio < 1.0 && newUsageRatio > 1.0) \|\| (usageRatio > 1.0 && newUsageRatio < 1.0) {
	// return the current replicas if the change would be too small,
	// or if the new usage ratio would cause a change in scale direction
	return currentReplicas, utilization, rawUtilization, timestamp, nil
	}

	// return the result, where the number of replicas considered is
	// however many replicas factored into our calculation
	return int32(math.Ceil(newUsageRatio * float64(len(metrics)))), utilization, rawUtilization, timestamp, nil
	}

	// GetRawResourceReplicas calculates the desired replica count based on a target resource utilization (as a raw milli-value)
	// for pods matching the given selector in the given namespace, and the current replica count
	func (c *ReplicaCalculator) GetRawResourceReplicas(currentReplicas int32, targetUtilization int64, resource v1.ResourceName, namespace string, selector labels.Selector) (replicaCount int32, utilization int64, timestamp time.Time, err error) {
	metrics, timestamp, err := c.metricsClient.GetResourceMetric(resource, namespace, selector)
	if err != nil {
	return 0, 0, time.Time{}, fmt.Errorf("unable to get metrics for resource %s: %v", resource, err)
	}

	replicaCount, utilization, err = c.calcPlainMetricReplicas(metrics, currentReplicas, targetUtilization, namespace, selector, resource)
	return replicaCount, utilization, timestamp, err
	}

	// GetMetricReplicas calculates the desired replica count based on a target metric utilization
	// (as a milli-value) for pods matching the given selector in the given namespace, and the
	// current replica count
	func (c *ReplicaCalculator) GetMetricReplicas(currentReplicas int32, targetUtilization int64, metricName string, namespace string, selector labels.Selector, metricSelector labels.Selector) (replicaCount int32, utilization int64, timestamp time.Time, err error) {
	metrics, timestamp, err := c.metricsClient.GetRawMetric(metricName, namespace, selector, metricSelector)
	if err != nil {
	return 0, 0, time.Time{}, fmt.Errorf("unable to get metric %s: %v", metricName, err)
	}

	replicaCount, utilization, err = c.calcPlainMetricReplicas(metrics, currentReplicas, targetUtilization, namespace, selector, v1.ResourceName(""))
	return replicaCount, utilization, timestamp, err
	}

	// calcPlainMetricReplicas calculates the desired replicas for plain (i.e. non-utilization percentage) metrics.
	func (c *ReplicaCalculator) calcPlainMetricReplicas(metrics metricsclient.PodMetricsInfo, currentReplicas int32, targetUtilization int64, namespace string, selector labels.Selector, resource v1.ResourceName) (replicaCount int32, utilization int64, err error) {

	podList, err := c.podLister.Pods(namespace).List(selector)
	if err != nil {
	return 0, 0, fmt.Errorf("unable to get pods while calculating replica count: %v", err)
	}

	if len(podList) == 0 {
	return 0, 0, fmt.Errorf("no pods returned by selector while calculating replica count")
	}

	readyPodCount, ignoredPods, missingPods := groupPods(podList, metrics, resource, c.cpuInitializationPeriod, c.delayOfInitialReadinessStatus)
	removeMetricsForPods(metrics, ignoredPods)

	if len(metrics) == 0 {
	return 0, 0, fmt.Errorf("did not receive metrics for any ready pods")
	}

	usageRatio, utilization := metricsclient.GetMetricUtilizationRatio(metrics, targetUtilization)

	rebalanceIgnored := len(ignoredPods) > 0 && usageRatio > 1.0

	if !rebalanceIgnored && len(missingPods) == 0 {
	if math.Abs(1.0-usageRatio) <= c.tolerance {
	// return the current replicas if the change would be too small
	return currentReplicas, utilization, nil
	}

	// if we don't have any unready or missing pods, we can calculate the new replica count now
	return int32(math.Ceil(usageRatio * float64(readyPodCount))), utilization, nil
	}

	if len(missingPods) > 0 {
	if usageRatio < 1.0 {
	// on a scale-down, treat missing pods as using 100% of the resource request
	for podName := range missingPods {
	metrics[podName] = metricsclient.PodMetric{Value: targetUtilization}
	}
	} else {
	// on a scale-up, treat missing pods as using 0% of the resource request
	for podName := range missingPods {
	metrics[podName] = metricsclient.PodMetric{Value: 0}
	}
	}
	}

	if rebalanceIgnored {
	// on a scale-up, treat unready pods as using 0% of the resource request
	for podName := range ignoredPods {
	metrics[podName] = metricsclient.PodMetric{Value: 0}
	}
	}

	// re-run the utilization calculation with our new numbers
	newUsageRatio, _ := metricsclient.GetMetricUtilizationRatio(metrics, targetUtilization)

	if math.Abs(1.0-newUsageRatio) <= c.tolerance \|\| (usageRatio < 1.0 && newUsageRatio > 1.0) \|\| (usageRatio > 1.0 && newUsageRatio < 1.0) {
	// return the current replicas if the change would be too small,
	// or if the new usage ratio would cause a change in scale direction
	return currentReplicas, utilization, nil
	}

	// return the result, where the number of replicas considered is
	// however many replicas factored into our calculation
	return int32(math.Ceil(newUsageRatio * float64(len(metrics)))), utilization, nil
	}

	// GetObjectMetricReplicas calculates the desired replica count based on a target metric utilization (as a milli-value)
	// for the given object in the given namespace, and the current replica count.
	func (c ReplicaCalculator) GetObjectMetricReplicas(currentReplicas int32, targetUtilization int64, metricName string, namespace string, objectRef autoscaling.CrossVersionObjectReference, selector labels.Selector, metricSelector labels.Selector) (replicaCount int32, utilization int64, timestamp time.Time, err error) {
	utilization, timestamp, err = c.metricsClient.GetObjectMetric(metricName, namespace, objectRef, metricSelector)
	if err != nil {
	return 0, 0, time.Time{}, fmt.Errorf("unable to get metric %s: %v on %s %s/%s", metricName, objectRef.Kind, namespace, objectRef.Name, err)
	}

	usageRatio := float64(utilization) / float64(targetUtilization)
	if math.Abs(1.0-usageRatio) <= c.tolerance {
	// return the current replicas if the change would be too small
	return currentReplicas, utilization, timestamp, nil
	}

	readyPodCount, err := c.getReadyPodsCount(namespace, selector)

	if err != nil {
	return 0, 0, time.Time{}, fmt.Errorf("unable to calculate ready pods: %s", err)
	}

	replicaCount = int32(math.Ceil(usageRatio * float64(readyPodCount)))

	return replicaCount, utilization, timestamp, nil
	}

	// @TODO(mattjmcnaughton) Many different functions in this module use variations
	// of this function. Make this function generic, so we don't repeat the same
	// logic in multiple places.
	func (c *ReplicaCalculator) getReadyPodsCount(namespace string, selector labels.Selector) (int64, error) {
	podList, err := c.podLister.Pods(namespace).List(selector)
	if err != nil {
	return 0, fmt.Errorf("unable to get pods while calculating replica count: %v", err)
	}

	if len(podList) == 0 {
	return 0, fmt.Errorf("no pods returned by selector while calculating replica count")
	}

	readyPodCount := 0

	for _, pod := range podList {
	if pod.Status.Phase == v1.PodRunning && podutil.IsPodReady(pod) {
	readyPodCount++
	}
	}

	return int64(readyPodCount), nil
	}

	// GetExternalMetricReplicas calculates the desired replica count based on a
	// target metric value (as a milli-value) for the external metric in the given
	// namespace, and the current replica count.
	func (c ReplicaCalculator) GetExternalMetricReplicas(currentReplicas int32, targetUtilization int64, metricName, namespace string, metricSelector metav1.LabelSelector, podSelector labels.Selector) (replicaCount int32, utilization int64, timestamp time.Time, err error) {
	metricLabelSelector, err := metav1.LabelSelectorAsSelector(metricSelector)
	if err != nil {
	return 0, 0, time.Time{}, err
	}
	metrics, timestamp, err := c.metricsClient.GetExternalMetric(metricName, namespace, metricLabelSelector)
	if err != nil {
	return 0, 0, time.Time{}, fmt.Errorf("unable to get external metric %s/%s/%+v: %s", namespace, metricName, metricSelector, err)
	}
	utilization = 0
	for _, val := range metrics {
	utilization = utilization + val
	}

	readyPodCount, err := c.getReadyPodsCount(namespace, podSelector)

	if err != nil {
	return 0, 0, time.Time{}, fmt.Errorf("unable to calculate ready pods: %s", err)
	}

	usageRatio := float64(utilization) / float64(targetUtilization)
	if math.Abs(1.0-usageRatio) <= c.tolerance {
	// return the current replicas if the change would be too small
	return currentReplicas, utilization, timestamp, nil
	}

	return int32(math.Ceil(usageRatio * float64(readyPodCount))), utilization, timestamp, nil
	}

	// GetExternalPerPodMetricReplicas calculates the desired replica count based on a
	// target metric value per pod (as a milli-value) for the external metric in the
	// given namespace, and the current replica count.
	func (c ReplicaCalculator) GetExternalPerPodMetricReplicas(currentReplicas int32, targetUtilizationPerPod int64, metricName, namespace string, metricSelector metav1.LabelSelector) (replicaCount int32, utilization int64, timestamp time.Time, err error) {
	metricLabelSelector, err := metav1.LabelSelectorAsSelector(metricSelector)
	if err != nil {
	return 0, 0, time.Time{}, err
	}
	metrics, timestamp, err := c.metricsClient.GetExternalMetric(metricName, namespace, metricLabelSelector)
	if err != nil {
	return 0, 0, time.Time{}, fmt.Errorf("unable to get external metric %s/%s/%+v: %s", namespace, metricName, metricSelector, err)
	}
	utilization = 0
	for _, val := range metrics {
	utilization = utilization + val
	}

	replicaCount = currentReplicas
	usageRatio := float64(utilization) / (float64(targetUtilizationPerPod) * float64(replicaCount))
	if math.Abs(1.0-usageRatio) > c.tolerance {
	// update number of replicas if the change is large enough
	replicaCount = int32(math.Ceil(float64(utilization) / float64(targetUtilizationPerPod)))
	}
	utilization = int64(math.Ceil(float64(utilization) / float64(currentReplicas)))
	return replicaCount, utilization, timestamp, nil
	}

	func groupPods(pods []*v1.Pod, metrics metricsclient.PodMetricsInfo, resource v1.ResourceName, cpuInitializationPeriod, delayOfInitialReadinessStatus time.Duration) (readyPodCount int, ignoredPods sets.String, missingPods sets.String) {
	missingPods = sets.NewString()
	ignoredPods = sets.NewString()
	for _, pod := range pods {
	if pod.DeletionTimestamp != nil \|\| pod.Status.Phase == v1.PodFailed {
	continue
	}
	metric, found := metrics[pod.Name]
	if !found {
	missingPods.Insert(pod.Name)
	continue
	}
	if resource == v1.ResourceCPU {
	var ignorePod bool
	_, condition := podutil.GetPodCondition(&pod.Status, v1.PodReady)
	if condition == nil \|\| pod.Status.StartTime == nil {
	ignorePod = true
	} else {
	// Pod still within possible initialisation period.
	if pod.Status.StartTime.Add(cpuInitializationPeriod).After(time.Now()) {
	// Ignore sample if pod is unready or one window of metric wasn't collected since last state transition.
	ignorePod = condition.Status == v1.ConditionFalse \|\| metric.Timestamp.Before(condition.LastTransitionTime.Time.Add(metric.Window))
	} else {
	// Ignore metric if pod is unready and it has never been ready.
	ignorePod = condition.Status == v1.ConditionFalse && pod.Status.StartTime.Add(delayOfInitialReadinessStatus).After(condition.LastTransitionTime.Time)
	}
	}
	if ignorePod {
	ignoredPods.Insert(pod.Name)
	continue
	}
	}
	readyPodCount++
	}
	return
	}

	func calculatePodRequests(pods []*v1.Pod, resource v1.ResourceName) (map[string]int64, error) {
	requests := make(map[string]int64, len(pods))
	for _, pod := range pods {
	podSum := int64(0)
	for _, container := range pod.Spec.Containers {
	if containerRequest, ok := container.Resources.Requests[resource]; ok {
	podSum += containerRequest.MilliValue()
	} else {
	return nil, fmt.Errorf("missing request for %s", resource)
	}
	}
	requests[pod.Name] = podSum
	}
	return requests, nil
	}

	func removeMetricsForPods(metrics metricsclient.PodMetricsInfo, pods sets.String) {
	for _, pod := range pods.UnsortedList() {
	delete(metrics, pod)
	}
	}