kubelet: Mark new terminal pods as non-finished in pod worker

The pod worker may recieve a new pod which is marked as terminal in
the runtime cache. This can occur if a pod is marked as terminal and the
kubelet is restarted.

The kubelet needs to drive these pods through the termination state
machine. If upon restart, the kubelet receives a pod which is terminal
based on runtime cache, it indicates that pod finished
`SyncTerminatingPod`, but it did not complete `SyncTerminatedPod`. The
pod worker needs ensure that `SyncTerminatedPod` will run on these pods.
To accomplish this, set `finished=False`, on the pod sync status, to
drive the pod through the rest of the state machine.

This will ensure that status manager and other kubelet subcomponents
(e.g. volume manager), will be aware of this pod and properly cleanup
all of the resources of the pod after the kubelet is restarted.

While making change, also update the comments to provide a bit more
background around why the kubelet needs to read the runtime pod cache
for newly synced terminal pods.

Signed-off-by: David Porter <david@porter.me>

pkg/kubelet/pod_workers.go

@@ -775,16 +775,23 @@ func (p *podWorkers) UpdatePod(options UpdatePodOptions) {
 		}
 		// if this pod is being synced for the first time, we need to make sure it is an active pod
 		if options.Pod != nil && (options.Pod.Status.Phase == v1.PodFailed || options.Pod.Status.Phase == v1.PodSucceeded) {
-			// check to see if the pod is not running and the pod is terminal.
-			// If this succeeds then record in the podWorker that it is terminated.
+			// Check to see if the pod is not running and the pod is terminal; if this succeeds then record in the podWorker that it is terminated.
+			// This is needed because after a kubelet restart, we need to ensure terminal pods will NOT be considered active in Pod Admission. See http://issues.k8s.io/105523
+			// However, `filterOutInactivePods`, considers pods that are actively terminating as active. As a result, `IsPodKnownTerminated()` needs to return true and thus `terminatedAt` needs to be set.
 			if statusCache, err := p.podCache.Get(uid); err == nil {
 				if isPodStatusCacheTerminal(statusCache) {
+					// At this point we know:
+					// (1) The pod is terminal based on the config source.
+					// (2) The pod is terminal based on the runtime cache.
+					// This implies that this pod had already completed `SyncTerminatingPod` sometime in the past. The pod is likely being synced for the first time due to a kubelet restart.
+					// These pods need to complete SyncTerminatedPod to ensure that all resources are cleaned and that the status manager makes the final status updates for the pod.
+					// As a result, set finished: false, to ensure a Terminated event will be sent and `SyncTerminatedPod` will run.
 					status = &podSyncStatus{
 						terminatedAt:       now,
 						terminatingAt:      now,
 						syncedAt:           now,
 						startedTerminating: true,
-						finished:           true,
+						finished:           false,
 						fullname:           kubecontainer.BuildPodFullName(name, ns),
 					}
 				}

pkg/kubelet/pod_workers_test.go

@@ -754,23 +754,41 @@ func TestUpdatePod(t *testing.T) {
 			expectKnownTerminated: true,
 		},
 		{
-			name: "a pod that is terminal and has never started is finished immediately if the runtime has a cached terminal state",
+			name: "a pod that is terminal and has never started advances to finished if the runtime has a cached terminal state",
 			update: UpdatePodOptions{
 				UpdateType: kubetypes.SyncPodCreate,
 				Pod:        newPodWithPhase("1", "done-pod", v1.PodSucceeded),
 			},
 			runtimeStatus: &kubecontainer.PodStatus{ /* we know about this pod */ },
-			expect: &podSyncStatus{
+			expectBeforeWorker: &podSyncStatus{
+				fullname:      "done-pod_ns",
+				syncedAt:      time.Unix(1, 0),
+				terminatingAt: time.Unix(1, 0),
+				terminatedAt:  time.Unix(1, 0),
+				pendingUpdate: &UpdatePodOptions{
+					UpdateType: kubetypes.SyncPodCreate,
+					Pod:        newPodWithPhase("1", "done-pod", v1.PodSucceeded),
+				},
+				finished:           false, // Should be marked as not finished initially (to ensure `SyncTerminatedPod` will run) and status will progress to terminated.
+				startedTerminating: true,
+				working:            true,
+			},
+			expect: hasContext(&podSyncStatus{
 				fullname:           "done-pod_ns",
 				syncedAt:           time.Unix(1, 0),
 				terminatingAt:      time.Unix(1, 0),
 				terminatedAt:       time.Unix(1, 0),
+				startedAt:          time.Unix(3, 0),
 				startedTerminating: true,
 				finished:           true,
+				activeUpdate: &UpdatePodOptions{
+					UpdateType: kubetypes.SyncPodSync,
+					Pod:        newPodWithPhase("1", "done-pod", v1.PodSucceeded),
+				},
 
 				// if we have never seen the pod before, a restart makes no sense
 				restartRequested: false,
-			},
+			}),
 			expectKnownTerminated: true,
 		},
 		{