Add IsUpTodate() to Cache interface.

This allows scheduler implementations to check if a NodeInfo object
matches the current state of the cache. Useful if the NodeInfo in
question came from a Snapshot() for example.

pkg/scheduler/schedulercache/BUILD

@@ -43,6 +43,7 @@ go_test(
         "//vendor/k8s.io/apimachinery/pkg/labels:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/types:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/intstr:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/util/wait:go_default_library",
         "//vendor/k8s.io/apiserver/pkg/util/feature:go_default_library",
     ],
 )

pkg/scheduler/schedulercache/cache.go

@@ -460,6 +460,13 @@ func (cache *schedulerCache) ListPDBs(selector labels.Selector) ([]*policy.PodDi
 	return pdbs, nil
 }
 
+func (cache *schedulerCache) IsUpToDate(n *NodeInfo) bool {
+	cache.mu.Lock()
+	defer cache.mu.Unlock()
+	node, ok := cache.nodes[n.Node().Name]
+	return ok && n.generation == node.generation
+}
+
 func (cache *schedulerCache) run() {
 	go wait.Until(cache.cleanupExpiredAssumedPods, cache.period, cache.stop)
 }

pkg/scheduler/schedulercache/cache_test.go

@@ -30,6 +30,7 @@ import (
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/intstr"
+	"k8s.io/apimachinery/pkg/util/wait"
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/kubernetes/pkg/features"
 	priorityutil "k8s.io/kubernetes/pkg/scheduler/algorithm/priorities/util"
@@ -1241,3 +1242,26 @@ func TestPDBOperations(t *testing.T) {
 		}
 	}
 }
+
+func TestIsUpToDate(t *testing.T) {
+	cache := New(time.Duration(0), wait.NeverStop)
+	if err := cache.AddNode(&v1.Node{ObjectMeta: metav1.ObjectMeta{Name: "n1"}}); err != nil {
+		t.Errorf("Could not add node: %v", err)
+	}
+	s := cache.Snapshot()
+	node := s.Nodes["n1"]
+	if !cache.IsUpToDate(node) {
+		t.Errorf("Node incorrectly marked as stale")
+	}
+	pod := &v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "p1", UID: "p1"}, Spec: v1.PodSpec{NodeName: "n1"}}
+	if err := cache.AddPod(pod); err != nil {
+		t.Errorf("Could not add pod: %v", err)
+	}
+	if cache.IsUpToDate(node) {
+		t.Errorf("Node incorrectly marked as up to date")
+	}
+	badNode := &NodeInfo{node: &v1.Node{ObjectMeta: metav1.ObjectMeta{Name: "n2"}}}
+	if cache.IsUpToDate(badNode) {
+		t.Errorf("Nonexistant node incorrectly marked as up to date")
+	}
+}

pkg/scheduler/schedulercache/interface.go

@@ -122,6 +122,9 @@ type Cache interface {
 
 	// Snapshot takes a snapshot on current cache
 	Snapshot() *Snapshot
+
+	// IsUpToDate returns true if the given NodeInfo matches the current data in the cache.
+	IsUpToDate(n *NodeInfo) bool
 }
 
 // Snapshot is a snapshot of cache state

pkg/scheduler/testing/fake_cache.go

@@ -105,3 +105,6 @@ func (f *FakeCache) FilteredList(filter schedulercache.PodFilter, selector label
 func (f *FakeCache) Snapshot() *schedulercache.Snapshot {
 	return &schedulercache.Snapshot{}
 }
+
+// IsUpToDate is a fake mthod for testing
+func (f *FakeCache) IsUpToDate(*schedulercache.NodeInfo) bool { return true }