// Run runs the Scheduler.
func Run(c schedulerserverconfig.CompletedConfig, stopCh <-chan struct{}) error {
	...
	// Apply algorithms based on feature gates.
	// TODO: make configurable?
	algorithmprovider.ApplyFeatureGates()
  ...
}  

// ApplyFeatureGates applies algorithm by feature gates.
func ApplyFeatureGates() {
	defaults.ApplyFeatureGates()
}

// ApplyFeatureGates applies algorithm by feature gates.
func ApplyFeatureGates() {
	if utilfeature.DefaultFeatureGate.Enabled(features.TaintNodesByCondition) {
		// Remove "CheckNodeCondition", "CheckNodeMemoryPressure", "CheckNodePIDPressurePred"
		// and "CheckNodeDiskPressure" predicates
		factory.RemoveFitPredicate(predicates.CheckNodeConditionPred)
		factory.RemoveFitPredicate(predicates.CheckNodeMemoryPressurePred)
		factory.RemoveFitPredicate(predicates.CheckNodeDiskPressurePred)
		factory.RemoveFitPredicate(predicates.CheckNodePIDPressurePred)
		// Remove key "CheckNodeCondition", "CheckNodeMemoryPressure" and "CheckNodeDiskPressure"
		// from ALL algorithm provider
		// The key will be removed from all providers which in algorithmProviderMap[]
		// if you just want remove specific provider, call func RemovePredicateKeyFromAlgoProvider()
		factory.RemovePredicateKeyFromAlgorithmProviderMap(predicates.CheckNodeConditionPred)
		factory.RemovePredicateKeyFromAlgorithmProviderMap(predicates.CheckNodeMemoryPressurePred)
		factory.RemovePredicateKeyFromAlgorithmProviderMap(predicates.CheckNodeDiskPressurePred)
		factory.RemovePredicateKeyFromAlgorithmProviderMap(predicates.CheckNodePIDPressurePred)

		// Fit is determined based on whether a pod can tolerate all of the node's taints
		factory.RegisterMandatoryFitPredicate(predicates.PodToleratesNodeTaintsPred, predicates.PodToleratesNodeTaints)
		// Fit is determined based on whether a pod can tolerate unschedulable of node
		factory.RegisterMandatoryFitPredicate(predicates.CheckNodeUnschedulablePred, predicates.CheckNodeUnschedulablePredicate)
		// Insert Key "PodToleratesNodeTaints" and "CheckNodeUnschedulable" To All Algorithm Provider
		// The key will insert to all providers which in algorithmProviderMap[]
		// if you just want insert to specific provider, call func InsertPredicateKeyToAlgoProvider()
		factory.InsertPredicateKeyToAlgorithmProviderMap(predicates.PodToleratesNodeTaintsPred)
		factory.InsertPredicateKeyToAlgorithmProviderMap(predicates.CheckNodeUnschedulablePred)

		glog.Warningf("TaintNodesByCondition is enabled, PodToleratesNodeTaints predicate is mandatory")
	}

	// Prioritizes nodes that satisfy pod's resource limits
	if utilfeature.DefaultFeatureGate.Enabled(features.ResourceLimitsPriorityFunction) {
		factory.RegisterPriorityFunction2("ResourceLimitsPriority", priorities.ResourceLimitsPriorityMap, nil, 1)
	}

}

func init() {
	// Register functions that extract metadata used by predicates and priorities computations.
	factory.RegisterPredicateMetadataProducerFactory(
		func(args factory.PluginFactoryArgs) algorithm.PredicateMetadataProducer {
			return predicates.NewPredicateMetadataFactory(args.PodLister)
		})
	factory.RegisterPriorityMetadataProducerFactory(
		func(args factory.PluginFactoryArgs) algorithm.PriorityMetadataProducer {
			return priorities.NewPriorityMetadataFactory(args.ServiceLister, args.ControllerLister, args.ReplicaSetLister, args.StatefulSetLister)
		})

	registerAlgorithmProvider(defaultPredicates(), defaultPriorities())

	// IMPORTANT NOTES for predicate developers:
	// We are using cached predicate result for pods belonging to the same equivalence class.
	// So when implementing a new predicate, you are expected to check whether the result
	// of your predicate function can be affected by related API object change (ADD/DELETE/UPDATE).
	// If yes, you are expected to invalidate the cached predicate result for related API object change.
	// For example:
	// https://github.com/kubernetes/kubernetes/blob/36a218e/plugin/pkg/scheduler/factory/factory.go#L422

	// Registers predicates and priorities that are not enabled by default, but user can pick when creating their
	// own set of priorities/predicates.

	// PodFitsPorts has been replaced by PodFitsHostPorts for better user understanding.
	// For backwards compatibility with 1.0, PodFitsPorts is registered as well.
	factory.RegisterFitPredicate("PodFitsPorts", predicates.PodFitsHostPorts)
	// Fit is defined based on the absence of port conflicts.
	// This predicate is actually a default predicate, because it is invoked from
	// predicates.GeneralPredicates()
	factory.RegisterFitPredicate(predicates.PodFitsHostPortsPred, predicates.PodFitsHostPorts)
	// Fit is determined by resource availability.
	// This predicate is actually a default predicate, because it is invoked from
	// predicates.GeneralPredicates()
	factory.RegisterFitPredicate(predicates.PodFitsResourcesPred, predicates.PodFitsResources)
	// Fit is determined by the presence of the Host parameter and a string match
	// This predicate is actually a default predicate, because it is invoked from
	// predicates.GeneralPredicates()
	factory.RegisterFitPredicate(predicates.HostNamePred, predicates.PodFitsHost)
	// Fit is determined by node selector query.
	factory.RegisterFitPredicate(predicates.MatchNodeSelectorPred, predicates.PodMatchNodeSelector)

	// ServiceSpreadingPriority is a priority config factory that spreads pods by minimizing
	// the number of pods (belonging to the same service) on the same node.
	// Register the factory so that it's available, but do not include it as part of the default priorities
	// Largely replaced by "SelectorSpreadPriority", but registered for backward compatibility with 1.0
	factory.RegisterPriorityConfigFactory(
		"ServiceSpreadingPriority",
		factory.PriorityConfigFactory{
			MapReduceFunction: func(args factory.PluginFactoryArgs) (algorithm.PriorityMapFunction, algorithm.PriorityReduceFunction) {
				return priorities.NewSelectorSpreadPriority(args.ServiceLister, algorithm.EmptyControllerLister{}, algorithm.EmptyReplicaSetLister{}, algorithm.EmptyStatefulSetLister{})
			},
			Weight: 1,
		},
	)
	// EqualPriority is a prioritizer function that gives an equal weight of one to all nodes
	// Register the priority function so that its available
	// but do not include it as part of the default priorities
	factory.RegisterPriorityFunction2("EqualPriority", core.EqualPriorityMap, nil, 1)
	// Optional, cluster-autoscaler friendly priority function - give used nodes higher priority.
	factory.RegisterPriorityFunction2("MostRequestedPriority", priorities.MostRequestedPriorityMap, nil, 1)
	factory.RegisterPriorityFunction2(
		"RequestedToCapacityRatioPriority",
		priorities.RequestedToCapacityRatioResourceAllocationPriorityDefault().PriorityMap,
		nil,
		1)
}

// Register functions that extract metadata used by predicates and priorities computations.
factory.RegisterPredicateMetadataProducerFactory(
	func(args factory.PluginFactoryArgs) algorithm.PredicateMetadataProducer {
		return predicates.NewPredicateMetadataFactory(args.PodLister)
	})
factory.RegisterPriorityMetadataProducerFactory(
	func(args factory.PluginFactoryArgs) algorithm.PriorityMetadataProducer {
		return priorities.NewPriorityMetadataFactory(args.ServiceLister, args.ControllerLister, args.ReplicaSetLister, args.StatefulSetLister)
	})

registerAlgorithmProvider(defaultPredicates(), defaultPriorities())

func registerAlgorithmProvider(predSet, priSet sets.String) {
	// Registers algorithm providers. By default we use 'DefaultProvider', but user can specify one to be used
	// by specifying flag.
	factory.RegisterAlgorithmProvider(factory.DefaultProvider, predSet, priSet)
	// Cluster autoscaler friendly scheduling algorithm.
	factory.RegisterAlgorithmProvider(ClusterAutoscalerProvider, predSet,
		copyAndReplace(priSet, "LeastRequestedPriority", "MostRequestedPriority"))
}

// PodFitsPorts has been replaced by PodFitsHostPorts for better user understanding.
// For backwards compatibility with 1.0, PodFitsPorts is registered as well.
factory.RegisterFitPredicate("PodFitsPorts", predicates.PodFitsHostPorts)
// Fit is defined based on the absence of port conflicts.
// This predicate is actually a default predicate, because it is invoked from
// predicates.GeneralPredicates()
factory.RegisterFitPredicate(predicates.PodFitsHostPortsPred, predicates.PodFitsHostPorts)
// Fit is determined by resource availability.
// This predicate is actually a default predicate, because it is invoked from
// predicates.GeneralPredicates()
factory.RegisterFitPredicate(predicates.PodFitsResourcesPred, predicates.PodFitsResources)
// Fit is determined by the presence of the Host parameter and a string match
// This predicate is actually a default predicate, because it is invoked from
// predicates.GeneralPredicates()
factory.RegisterFitPredicate(predicates.HostNamePred, predicates.PodFitsHost)
// Fit is determined by node selector query.
factory.RegisterFitPredicate(predicates.MatchNodeSelectorPred, predicates.PodMatchNodeSelector)

// EqualPriority is a prioritizer function that gives an equal weight of one to all nodes
// Register the priority function so that its available
// but do not include it as part of the default priorities
factory.RegisterPriorityFunction2("EqualPriority", core.EqualPriorityMap, nil, 1)
// Optional, cluster-autoscaler friendly priority function - give used nodes higher priority.
factory.RegisterPriorityFunction2("MostRequestedPriority", priorities.MostRequestedPriorityMap, nil, 1)
factory.RegisterPriorityFunction2(
	"RequestedToCapacityRatioPriority",
	priorities.RequestedToCapacityRatioResourceAllocationPriorityDefault().PriorityMap,
	nil,
	1)

func defaultPredicates() sets.String {
	return sets.NewString(
		// Fit is determined by volume zone requirements.
		factory.RegisterFitPredicateFactory(
			predicates.NoVolumeZoneConflictPred,
			func(args factory.PluginFactoryArgs) algorithm.FitPredicate {
				return predicates.NewVolumeZonePredicate(args.PVInfo, args.PVCInfo, args.StorageClassInfo)
			},
		),
		// Fit is determined by whether or not there would be too many AWS EBS volumes attached to the node
		factory.RegisterFitPredicateFactory(
			predicates.MaxEBSVolumeCountPred,
			func(args factory.PluginFactoryArgs) algorithm.FitPredicate {
				return predicates.NewMaxPDVolumeCountPredicate(predicates.EBSVolumeFilterType, args.PVInfo, args.PVCInfo)
			},
		),
		// Fit is determined by whether or not there would be too many GCE PD volumes attached to the node
		factory.RegisterFitPredicateFactory(
			predicates.MaxGCEPDVolumeCountPred,
			func(args factory.PluginFactoryArgs) algorithm.FitPredicate {
				return predicates.NewMaxPDVolumeCountPredicate(predicates.GCEPDVolumeFilterType, args.PVInfo, args.PVCInfo)
			},
		),
		// Fit is determined by whether or not there would be too many Azure Disk volumes attached to the node
		factory.RegisterFitPredicateFactory(
			predicates.MaxAzureDiskVolumeCountPred,
			func(args factory.PluginFactoryArgs) algorithm.FitPredicate {
				return predicates.NewMaxPDVolumeCountPredicate(predicates.AzureDiskVolumeFilterType, args.PVInfo, args.PVCInfo)
			},
		),
		factory.RegisterFitPredicateFactory(
			predicates.MaxCSIVolumeCountPred,
			func(args factory.PluginFactoryArgs) algorithm.FitPredicate {
				return predicates.NewCSIMaxVolumeLimitPredicate(args.PVInfo, args.PVCInfo)
			},
		),
		// Fit is determined by inter-pod affinity.
		factory.RegisterFitPredicateFactory(
			predicates.MatchInterPodAffinityPred,
			func(args factory.PluginFactoryArgs) algorithm.FitPredicate {
				return predicates.NewPodAffinityPredicate(args.NodeInfo, args.PodLister)
			},
		),

		// Fit is determined by non-conflicting disk volumes.
		factory.RegisterFitPredicate(predicates.NoDiskConflictPred, predicates.NoDiskConflict),

		// GeneralPredicates are the predicates that are enforced by all Kubernetes components
		// (e.g. kubelet and all schedulers)
		factory.RegisterFitPredicate(predicates.GeneralPred, predicates.GeneralPredicates),

		// Fit is determined by node memory pressure condition.
		factory.RegisterFitPredicate(predicates.CheckNodeMemoryPressurePred, predicates.CheckNodeMemoryPressurePredicate),

		// Fit is determined by node disk pressure condition.
		factory.RegisterFitPredicate(predicates.CheckNodeDiskPressurePred, predicates.CheckNodeDiskPressurePredicate),

		// Fit is determined by node pid pressure condition.
		factory.RegisterFitPredicate(predicates.CheckNodePIDPressurePred, predicates.CheckNodePIDPressurePredicate),

		// Fit is determined by node conditions: not ready, network unavailable or out of disk.
		factory.RegisterMandatoryFitPredicate(predicates.CheckNodeConditionPred, predicates.CheckNodeConditionPredicate),

		// Fit is determined based on whether a pod can tolerate all of the node's taints
		factory.RegisterFitPredicate(predicates.PodToleratesNodeTaintsPred, predicates.PodToleratesNodeTaints),

		// Fit is determined by volume topology requirements.
		factory.RegisterFitPredicateFactory(
			predicates.CheckVolumeBindingPred,
			func(args factory.PluginFactoryArgs) algorithm.FitPredicate {
				return predicates.NewVolumeBindingPredicate(args.VolumeBinder)
			},
		),
	)
}

func defaultPriorities() sets.String {
	return sets.NewString(
		// spreads pods by minimizing the number of pods (belonging to the same service or replication controller) on the same node.
		factory.RegisterPriorityConfigFactory(
			"SelectorSpreadPriority",
			factory.PriorityConfigFactory{
				MapReduceFunction: func(args factory.PluginFactoryArgs) (algorithm.PriorityMapFunction, algorithm.PriorityReduceFunction) {
					return priorities.NewSelectorSpreadPriority(args.ServiceLister, args.ControllerLister, args.ReplicaSetLister, args.StatefulSetLister)
				},
				Weight: 1,
			},
		),
		// pods should be placed in the same topological domain (e.g. same node, same rack, same zone, same power domain, etc.)
		// as some other pods, or, conversely, should not be placed in the same topological domain as some other pods.
		factory.RegisterPriorityConfigFactory(
			"InterPodAffinityPriority",
			factory.PriorityConfigFactory{
				Function: func(args factory.PluginFactoryArgs) algorithm.PriorityFunction {
					return priorities.NewInterPodAffinityPriority(args.NodeInfo, args.NodeLister, args.PodLister, args.HardPodAffinitySymmetricWeight)
				},
				Weight: 1,
			},
		),

		// Prioritize nodes by least requested utilization.
		factory.RegisterPriorityFunction2("LeastRequestedPriority", priorities.LeastRequestedPriorityMap, nil, 1),

		// Prioritizes nodes to help achieve balanced resource usage
		factory.RegisterPriorityFunction2("BalancedResourceAllocation", priorities.BalancedResourceAllocationMap, nil, 1),

		// Set this weight large enough to override all other priority functions.
		// TODO: Figure out a better way to do this, maybe at same time as fixing #24720.
		factory.RegisterPriorityFunction2("NodePreferAvoidPodsPriority", priorities.CalculateNodePreferAvoidPodsPriorityMap, nil, 10000),

		// Prioritizes nodes that have labels matching NodeAffinity
		factory.RegisterPriorityFunction2("NodeAffinityPriority", priorities.CalculateNodeAffinityPriorityMap, priorities.CalculateNodeAffinityPriorityReduce, 1),

		// Prioritizes nodes that marked with taint which pod can tolerate.
		factory.RegisterPriorityFunction2("TaintTolerationPriority", priorities.ComputeTaintTolerationPriorityMap, priorities.ComputeTaintTolerationPriorityReduce, 1),

		// ImageLocalityPriority prioritizes nodes that have images requested by the pod present.
		factory.RegisterPriorityFunction2("ImageLocalityPriority", priorities.ImageLocalityPriorityMap, nil, 1),
	)
}