- scheduler extenders that are capable of maintaining their own

node cache don't need to get all the information about every
  candidate node. For huge clusters, sending full node information
  of all nodes in the cluster on the wire every time a pod is scheduled
  is expensive. If the scheduler is capable of caching node information
  along with its capabilities, sending node name alone is sufficient.
  These changes provide that optimization in a backward compatible way

- removed the inadvertent signature change of Prioritize() function
- added defensive checks as suggested
-  added annotation specific test case
- updated the comments in the scheduler types
- got rid of apiVersion thats unused
- using *v1.NodeList as suggested
- backing out pod annotation update related changes made in the
  1st commit
- Adjusted the comments in types.go and v1/types.go as suggested
  in the code review

plugin/pkg/scheduler/algorithm/scheduler_interface.go

@@ -19,6 +19,7 @@ package algorithm
 import (
 	"k8s.io/kubernetes/pkg/api/v1"
 	schedulerapi "k8s.io/kubernetes/plugin/pkg/scheduler/api"
+	"k8s.io/kubernetes/plugin/pkg/scheduler/schedulercache"
 )
 
 // SchedulerExtender is an interface for external processes to influence scheduling
@@ -28,7 +29,7 @@ type SchedulerExtender interface {
 	// Filter based on extender-implemented predicate functions. The filtered list is
 	// expected to be a subset of the supplied list. failedNodesMap optionally contains
 	// the list of failed nodes and failure reasons.
-	Filter(pod *v1.Pod, nodes []*v1.Node) (filteredNodes []*v1.Node, failedNodesMap schedulerapi.FailedNodesMap, err error)
+	Filter(pod *v1.Pod, nodes []*v1.Node, nodeNameToInfo map[string]*schedulercache.NodeInfo) (filteredNodes []*v1.Node, failedNodesMap schedulerapi.FailedNodesMap, err error)
 
 	// Prioritize based on extender-implemented priority functions. The returned scores & weight
 	// are used to compute the weighted score for an extender. The weighted scores are added to