Scheduler Extender

// https://github.com/kubernetes/kubernetes/blob/master/pkg/scheduler/framework/extender.go#L24-L72
// Extender is an interface for external processes to influence scheduling
// decisions made by Kubernetes. This is typically needed for resources not directly
// managed by Kubernetes.
type Extender interface {
    // Name() returns a unique name that identifies the extender.
	Name() string
	// Filter based on extender-implemented predicate functions. The filtered list is
	// expected to be a subset of the supplied list.
	// The failedNodes and failedAndUnresolvableNodes optionally contains the list
	// of failed nodes and failure reasons, except nodes in the latter are
	// unresolvable.
	Filter(pod *v1.Pod, nodes []*v1.Node) (filteredNodes []*v1.Node, failedNodesMap extenderv1.FailedNodesMap, failedAndUnresolvable extenderv1.FailedNodesMap, err error)
    // Prioritize based on extender-implemented priority functions
	// The returned scores and weight are used to compute the weighted score for an extender. 
    // The weighted scores are added t the scores computed by Kubernetes scheduler. The total 
	// scores are used to do the host selection.
	
	Prioritize(pod *v1.Pod, nodes []*v1.Node) (hostPriorities *extenderv1.HostPriorityList, weight int64, err error)
    // Bind() delegates the action of binding a Pod to a node to the extender.
	Bind(binding *v1.Binding) error
	// IsBinder() returns whether this extender is configured for the Bind() method.
	IsBinder() bool
	// sInterested() returns true if at least one extended resource requested by this 
	// Pod is managed by this extender.
	IsInterested(pod *v1.Pod) bool
	// ProcessPreemption() returns nodes with their victim Pods processed by the extender based on the following:
	//   1. Pod to schedule
	//   2. Candidate nodes and victim pods (nodeNameToVictims) generated by previous scheduling process.
	// The possible changes made by extender may include:
	//   1. Subset of given candidate nodes after the preemption phase of extender.
	//   2. A different set of victim Pods for every given candidate node after the preemption phase of extender."
	ProcessPreemption(
		pod *v1.Pod,
		nodeNameToVictims map[string]*extenderv1.Victims,
		nodeInfos NodeInfoLister,
	) (map[string]*extenderv1.Victims, error)
	// The SupportsPreemption() function returns whether or not the scheduler extender supports preemption.
	SupportsPreemption() bool
	// The IsIgnorable() function returns true, which indicates that scheduling should not fail when this extender is unavailable.
	// This gives the scheduler the ability to fail fast and tolerate non-critical extenders as well.
	IsIgnorable() bool
}