Sort critical pods before admission

pkg/kubelet/kubelet.go

@@ -1909,8 +1909,21 @@ func (kl *Kubelet) handleMirrorPod(mirrorPod *v1.Pod, start time.Time) {
 // a config source.
 func (kl *Kubelet) HandlePodAdditions(pods []*v1.Pod) {
 	start := kl.clock.Now()
-	sort.Sort(sliceutils.PodsByCreationTime(pods))
-	for _, pod := range pods {
+
+	// Pass critical pods through admission check first.
+	var criticalPods []*v1.Pod
+	var nonCriticalPods []*v1.Pod
+	for _, p := range pods {
+		if kubepod.IsCriticalPod(p) {
+			criticalPods = append(criticalPods, p)
+		} else {
+			nonCriticalPods = append(nonCriticalPods, p)
+		}
+	}
+	sort.Sort(sliceutils.PodsByCreationTime(criticalPods))
+	sort.Sort(sliceutils.PodsByCreationTime(nonCriticalPods))
+
+	for _, pod := range append(criticalPods, nonCriticalPods...) {
 		existingPods := kl.podManager.GetPods()
 		// Always add the pod to the pod manager. Kubelet relies on the pod
 		// manager as the source of truth for the desired state. If a pod does

pkg/kubelet/kubelet_test.go

@@ -461,6 +461,68 @@ func TestHandlePortConflicts(t *testing.T) {
 	require.Equal(t, v1.PodPending, status.Phase)
 }
 
+// Tests that we sort pods based on criticality.
+func TestCriticalPrioritySorting(t *testing.T) {
+	testKubelet := newTestKubelet(t, false /* controllerAttachDetachEnabled */)
+	kl := testKubelet.kubelet
+	nodes := []v1.Node{
+		{ObjectMeta: v1.ObjectMeta{Name: testKubeletHostname},
+			Status: v1.NodeStatus{Capacity: v1.ResourceList{}, Allocatable: v1.ResourceList{
+				v1.ResourceCPU:    *resource.NewMilliQuantity(10, resource.DecimalSI),
+				v1.ResourceMemory: *resource.NewQuantity(100, resource.BinarySI),
+				v1.ResourcePods:   *resource.NewQuantity(40, resource.DecimalSI),
+			}}},
+	}
+	kl.nodeLister = testNodeLister{nodes: nodes}
+	kl.nodeInfo = testNodeInfo{nodes: nodes}
+	testKubelet.fakeCadvisor.On("MachineInfo").Return(&cadvisorapi.MachineInfo{}, nil)
+	testKubelet.fakeCadvisor.On("ImagesFsInfo").Return(cadvisorapiv2.FsInfo{}, nil)
+	testKubelet.fakeCadvisor.On("RootFsInfo").Return(cadvisorapiv2.FsInfo{}, nil)
+
+	spec := v1.PodSpec{NodeName: string(kl.nodeName),
+		Containers: []v1.Container{{Resources: v1.ResourceRequirements{
+			Requests: v1.ResourceList{
+				"memory": resource.MustParse("90"),
+			},
+		}}}}
+	pods := []*v1.Pod{
+		podWithUidNameNsSpec("000000000", "newpod", "foo", spec),
+		podWithUidNameNsSpec("987654321", "oldpod", "foo", spec),
+		podWithUidNameNsSpec("123456789", "middlepod", "foo", spec),
+	}
+
+	// Pods are not sorted by creation time.
+	startTime := time.Now()
+	pods[0].CreationTimestamp = metav1.NewTime(startTime.Add(10 * time.Second))
+	pods[1].CreationTimestamp = metav1.NewTime(startTime)
+	pods[2].CreationTimestamp = metav1.NewTime(startTime.Add(1 * time.Second))
+
+	// Make the middle and new pod critical, the middle pod should win
+	// even though it comes later in the list
+	critical := map[string]string{kubetypes.CriticalPodAnnotationKey: ""}
+	pods[0].Annotations = critical
+	pods[1].Annotations = map[string]string{}
+	pods[2].Annotations = critical
+
+	// The non-critical pod should be rejected
+	notfittingPods := []*v1.Pod{pods[0], pods[1]}
+	fittingPod := pods[2]
+
+	kl.HandlePodAdditions(pods)
+	// Check pod status stored in the status map.
+	// notfittingPod should be Failed
+	for _, p := range notfittingPods {
+		status, found := kl.statusManager.GetPodStatus(p.UID)
+		require.True(t, found, "Status of pod %q is not found in the status map", p.UID)
+		require.Equal(t, v1.PodFailed, status.Phase)
+	}
+
+	// fittingPod should be Pending
+	status, found := kl.statusManager.GetPodStatus(fittingPod.UID)
+	require.True(t, found, "Status of pod %q is not found in the status map", fittingPod.UID)
+	require.Equal(t, v1.PodPending, status.Phase)
+}
+
 // Tests that we handle host name conflicts correctly by setting the failed status in status map.
 func TestHandleHostNameConflicts(t *testing.T) {
 	testKubelet := newTestKubelet(t, false /* controllerAttachDetachEnabled */)