/*
Copyright 2014 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

//go:generate mockgen -source=status_manager.go -destination=testing/mock_pod_status_provider.go -package=testing PodStatusProvider
package status

import (
	"context"
	"fmt"
	"sort"
	"strings"
	"sync"
	"time"

	clientset "k8s.io/client-go/kubernetes"

	v1 "k8s.io/api/core/v1"
	apiequality "k8s.io/apimachinery/pkg/api/equality"
	"k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/diff"
	"k8s.io/apimachinery/pkg/util/wait"
	utilfeature "k8s.io/apiserver/pkg/util/feature"
	"k8s.io/klog/v2"
	podutil "k8s.io/kubernetes/pkg/api/v1/pod"
	"k8s.io/kubernetes/pkg/features"
	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
	"k8s.io/kubernetes/pkg/kubelet/metrics"
	kubepod "k8s.io/kubernetes/pkg/kubelet/pod"
	kubetypes "k8s.io/kubernetes/pkg/kubelet/types"
	statusutil "k8s.io/kubernetes/pkg/util/pod"
)

// A wrapper around v1.PodStatus that includes a version to enforce that stale pod statuses are
// not sent to the API server.
type versionedPodStatus struct {
	// version is a monotonically increasing version number (per pod).
	version uint64
	// Pod name & namespace, for sending updates to API server.
	podName      string
	podNamespace string
	// at is the time at which the most recent status update was detected
	at time.Time

	status v1.PodStatus
}

type podStatusSyncRequest struct {
	podUID types.UID
	status versionedPodStatus
}

// Updates pod statuses in apiserver. Writes only when new status has changed.
// All methods are thread-safe.
type manager struct {
	kubeClient clientset.Interface
	podManager kubepod.Manager
	// Map from pod UID to sync status of the corresponding pod.
	podStatuses      map[types.UID]versionedPodStatus
	podStatusesLock  sync.RWMutex
	podStatusChannel chan podStatusSyncRequest
	// Map from (mirror) pod UID to latest status version successfully sent to the API server.
	// apiStatusVersions must only be accessed from the sync thread.
	apiStatusVersions map[kubetypes.MirrorPodUID]uint64
	podDeletionSafety PodDeletionSafetyProvider

	podStartupLatencyHelper PodStartupLatencyStateHelper
}

// PodStatusProvider knows how to provide status for a pod. It's intended to be used by other components
// that need to introspect status.
type PodStatusProvider interface {
	// GetPodStatus returns the cached status for the provided pod UID, as well as whether it
	// was a cache hit.
	GetPodStatus(uid types.UID) (v1.PodStatus, bool)
}

// PodDeletionSafetyProvider provides guarantees that a pod can be safely deleted.
type PodDeletionSafetyProvider interface {
	// PodResourcesAreReclaimed returns true if the pod can safely be deleted.
	PodResourcesAreReclaimed(pod *v1.Pod, status v1.PodStatus) bool
	// PodCouldHaveRunningContainers returns true if the pod could have running containers.
	PodCouldHaveRunningContainers(pod *v1.Pod) bool
}

type PodStartupLatencyStateHelper interface {
	RecordStatusUpdated(pod *v1.Pod)
	DeletePodStartupState(podUID types.UID)
}

// Manager is the Source of truth for kubelet pod status, and should be kept up-to-date with
// the latest v1.PodStatus. It also syncs updates back to the API server.
type Manager interface {
	PodStatusProvider

	// Start the API server status sync loop.
	Start()

	// SetPodStatus caches updates the cached status for the given pod, and triggers a status update.
	SetPodStatus(pod *v1.Pod, status v1.PodStatus)

	// SetContainerReadiness updates the cached container status with the given readiness, and
	// triggers a status update.
	SetContainerReadiness(podUID types.UID, containerID kubecontainer.ContainerID, ready bool)

	// SetContainerStartup updates the cached container status with the given startup, and
	// triggers a status update.
	SetContainerStartup(podUID types.UID, containerID kubecontainer.ContainerID, started bool)

	// TerminatePod resets the container status for the provided pod to terminated and triggers
	// a status update.
	TerminatePod(pod *v1.Pod)

	// RemoveOrphanedStatuses scans the status cache and removes any entries for pods not included in
	// the provided podUIDs.
	RemoveOrphanedStatuses(podUIDs map[types.UID]bool)
}

const syncPeriod = 10 * time.Second

// NewManager returns a functional Manager.
func NewManager(kubeClient clientset.Interface, podManager kubepod.Manager, podDeletionSafety PodDeletionSafetyProvider, podStartupLatencyHelper PodStartupLatencyStateHelper) Manager {
	return &manager{
		kubeClient:              kubeClient,
		podManager:              podManager,
		podStatuses:             make(map[types.UID]versionedPodStatus),
		podStatusChannel:        make(chan podStatusSyncRequest, 1000), // Buffer up to 1000 statuses
		apiStatusVersions:       make(map[kubetypes.MirrorPodUID]uint64),
		podDeletionSafety:       podDeletionSafety,
		podStartupLatencyHelper: podStartupLatencyHelper,
	}
}

// isPodStatusByKubeletEqual returns true if the given pod statuses are equal when non-kubelet-owned
// pod conditions are excluded.
// This method normalizes the status before comparing so as to make sure that meaningless
// changes will be ignored.
func isPodStatusByKubeletEqual(oldStatus, status *v1.PodStatus) bool {
	oldCopy := oldStatus.DeepCopy()
	for _, c := range status.Conditions {
		// both owned and shared conditions are used for kubelet status equality
		if kubetypes.PodConditionByKubelet(c.Type) || kubetypes.PodConditionSharedByKubelet(c.Type) {
			_, oc := podutil.GetPodCondition(oldCopy, c.Type)
			if oc == nil || oc.Status != c.Status || oc.Message != c.Message || oc.Reason != c.Reason {
				return false
			}
		}
	}
	oldCopy.Conditions = status.Conditions
	return apiequality.Semantic.DeepEqual(oldCopy, status)
}

func (m *manager) Start() {
	// Don't start the status manager if we don't have a client. This will happen
	// on the master, where the kubelet is responsible for bootstrapping the pods
	// of the master components.
	if m.kubeClient == nil {
		klog.InfoS("Kubernetes client is nil, not starting status manager")
		return
	}

	klog.InfoS("Starting to sync pod status with apiserver")

	//nolint:staticcheck // SA1015 Ticker can leak since this is only called once and doesn't handle termination.
	syncTicker := time.NewTicker(syncPeriod).C

	// syncPod and syncBatch share the same go routine to avoid sync races.
	go wait.Forever(func() {
		for {
			select {
			case syncRequest := <-m.podStatusChannel:
				klog.V(5).InfoS("Status Manager: syncing pod with status from podStatusChannel",
					"podUID", syncRequest.podUID,
					"statusVersion", syncRequest.status.version,
					"status", syncRequest.status.status)
				m.syncPod(syncRequest.podUID, syncRequest.status)
			case <-syncTicker:
				klog.V(5).InfoS("Status Manager: syncing batch")
				// remove any entries in the status channel since the batch will handle them
				for i := len(m.podStatusChannel); i > 0; i-- {
					<-m.podStatusChannel
				}
				m.syncBatch()
			}
		}
	}, 0)
}

func (m *manager) GetPodStatus(uid types.UID) (v1.PodStatus, bool) {
	m.podStatusesLock.RLock()
	defer m.podStatusesLock.RUnlock()
	status, ok := m.podStatuses[types.UID(m.podManager.TranslatePodUID(uid))]
	return status.status, ok
}

func (m *manager) SetPodStatus(pod *v1.Pod, status v1.PodStatus) {
	m.podStatusesLock.Lock()
	defer m.podStatusesLock.Unlock()

	// Make sure we're caching a deep copy.
	status = *status.DeepCopy()

	// Force a status update if deletion timestamp is set. This is necessary
	// because if the pod is in the non-running state, the pod worker still
	// needs to be able to trigger an update and/or deletion.
	m.updateStatusInternal(pod, status, pod.DeletionTimestamp != nil)
}

func (m *manager) SetContainerReadiness(podUID types.UID, containerID kubecontainer.ContainerID, ready bool) {
	m.podStatusesLock.Lock()
	defer m.podStatusesLock.Unlock()

	pod, ok := m.podManager.GetPodByUID(podUID)
	if !ok {
		klog.V(4).InfoS("Pod has been deleted, no need to update readiness", "podUID", string(podUID))
		return
	}

	oldStatus, found := m.podStatuses[pod.UID]
	if !found {
		klog.InfoS("Container readiness changed before pod has synced",
			"pod", klog.KObj(pod),
			"containerID", containerID.String())
		return
	}

	// Find the container to update.
	containerStatus, _, ok := findContainerStatus(&oldStatus.status, containerID.String())
	if !ok {
		klog.InfoS("Container readiness changed for unknown container",
			"pod", klog.KObj(pod),
			"containerID", containerID.String())
		return
	}

	if containerStatus.Ready == ready {
		klog.V(4).InfoS("Container readiness unchanged",
			"ready", ready,
			"pod", klog.KObj(pod),
			"containerID", containerID.String())
		return
	}

	// Make sure we're not updating the cached version.
	status := *oldStatus.status.DeepCopy()
	containerStatus, _, _ = findContainerStatus(&status, containerID.String())
	containerStatus.Ready = ready

	// updateConditionFunc updates the corresponding type of condition
	updateConditionFunc := func(conditionType v1.PodConditionType, condition v1.PodCondition) {
		conditionIndex := -1
		for i, condition := range status.Conditions {
			if condition.Type == conditionType {
				conditionIndex = i
				break
			}
		}
		if conditionIndex != -1 {
			status.Conditions[conditionIndex] = condition
		} else {
			klog.InfoS("PodStatus missing condition type", "conditionType", conditionType, "status", status)
			status.Conditions = append(status.Conditions, condition)
		}
	}
	updateConditionFunc(v1.PodReady, GeneratePodReadyCondition(&pod.Spec, status.Conditions, status.ContainerStatuses, status.Phase))
	updateConditionFunc(v1.ContainersReady, GenerateContainersReadyCondition(&pod.Spec, status.ContainerStatuses, status.Phase))
	m.updateStatusInternal(pod, status, false)
}

func (m *manager) SetContainerStartup(podUID types.UID, containerID kubecontainer.ContainerID, started bool) {
	m.podStatusesLock.Lock()
	defer m.podStatusesLock.Unlock()

	pod, ok := m.podManager.GetPodByUID(podUID)
	if !ok {
		klog.V(4).InfoS("Pod has been deleted, no need to update startup", "podUID", string(podUID))
		return
	}

	oldStatus, found := m.podStatuses[pod.UID]
	if !found {
		klog.InfoS("Container startup changed before pod has synced",
			"pod", klog.KObj(pod),
			"containerID", containerID.String())
		return
	}

	// Find the container to update.
	containerStatus, _, ok := findContainerStatus(&oldStatus.status, containerID.String())
	if !ok {
		klog.InfoS("Container startup changed for unknown container",
			"pod", klog.KObj(pod),
			"containerID", containerID.String())
		return
	}

	if containerStatus.Started != nil && *containerStatus.Started == started {
		klog.V(4).InfoS("Container startup unchanged",
			"pod", klog.KObj(pod),
			"containerID", containerID.String())
		return
	}

	// Make sure we're not updating the cached version.
	status := *oldStatus.status.DeepCopy()
	containerStatus, _, _ = findContainerStatus(&status, containerID.String())
	containerStatus.Started = &started

	m.updateStatusInternal(pod, status, false)
}

func findContainerStatus(status *v1.PodStatus, containerID string) (containerStatus *v1.ContainerStatus, init bool, ok bool) {
	// Find the container to update.
	for i, c := range status.ContainerStatuses {
		if c.ContainerID == containerID {
			return &status.ContainerStatuses[i], false, true
		}
	}

	for i, c := range status.InitContainerStatuses {
		if c.ContainerID == containerID {
			return &status.InitContainerStatuses[i], true, true
		}
	}

	return nil, false, false

}

// TerminatePod ensures that the status of containers is properly defaulted at the end of the pod
// lifecycle. As the Kubelet must reconcile with the container runtime to observe container status
// there is always the possibility we are unable to retrieve one or more container statuses due to
// garbage collection, admin action, or loss of temporary data on a restart. This method ensures
// that any absent container status is treated as a failure so that we do not incorrectly describe
// the pod as successful. If we have not yet initialized the pod in the presence of init containers,
// the init container failure status is sufficient to describe the pod as failing, and we do not need
// to override waiting containers (unless there is evidence the pod previously started those containers).
func (m *manager) TerminatePod(pod *v1.Pod) {
	m.podStatusesLock.Lock()
	defer m.podStatusesLock.Unlock()

	// ensure that all containers have a terminated state - because we do not know whether the container
	// was successful, always report an error
	oldStatus := &pod.Status
	if cachedStatus, ok := m.podStatuses[pod.UID]; ok {
		oldStatus = &cachedStatus.status
	}
	status := *oldStatus.DeepCopy()

	// once a pod has initialized, any missing status is treated as a failure
	if hasPodInitialized(pod) {
		for i := range status.ContainerStatuses {
			if status.ContainerStatuses[i].State.Terminated != nil {
				continue
			}
			status.ContainerStatuses[i].State = v1.ContainerState{
				Terminated: &v1.ContainerStateTerminated{
					Reason:   "ContainerStatusUnknown",
					Message:  "The container could not be located when the pod was terminated",
					ExitCode: 137,
				},
			}
		}
	}

	// all but the final suffix of init containers which have no evidence of a container start are
	// marked as failed containers
	for i := range initializedContainers(status.InitContainerStatuses) {
		if status.InitContainerStatuses[i].State.Terminated != nil {
			continue
		}
		status.InitContainerStatuses[i].State = v1.ContainerState{
			Terminated: &v1.ContainerStateTerminated{
				Reason:   "ContainerStatusUnknown",
				Message:  "The container could not be located when the pod was terminated",
				ExitCode: 137,
			},
		}
	}

	klog.V(5).InfoS("TerminatePod calling updateStatusInternal", "pod", klog.KObj(pod), "podUID", pod.UID)
	m.updateStatusInternal(pod, status, true)
}

// hasPodInitialized returns true if the pod has no evidence of ever starting a regular container, which
// implies those containers should not be transitioned to terminated status.
func hasPodInitialized(pod *v1.Pod) bool {
	// a pod without init containers is always initialized
	if len(pod.Spec.InitContainers) == 0 {
		return true
	}
	// if any container has ever moved out of waiting state, the pod has initialized
	for _, status := range pod.Status.ContainerStatuses {
		if status.LastTerminationState.Terminated != nil || status.State.Waiting == nil {
			return true
		}
	}
	// if the last init container has ever completed with a zero exit code, the pod is initialized
	if l := len(pod.Status.InitContainerStatuses); l > 0 {
		container := pod.Status.InitContainerStatuses[l-1]
		if state := container.LastTerminationState; state.Terminated != nil && state.Terminated.ExitCode == 0 {
			return true
		}
		if state := container.State; state.Terminated != nil && state.Terminated.ExitCode == 0 {
			return true
		}
	}
	// otherwise the pod has no record of being initialized
	return false
}

// initializedContainers returns all status except for suffix of containers that are in Waiting
// state, which is the set of containers that have attempted to start at least once. If all containers
// are Watiing, the first container is always returned.
func initializedContainers(containers []v1.ContainerStatus) []v1.ContainerStatus {
	for i := len(containers) - 1; i >= 0; i-- {
		if containers[i].State.Waiting == nil || containers[i].LastTerminationState.Terminated != nil {
			return containers[0 : i+1]
		}
	}
	// always return at least one container
	if len(containers) > 0 {
		return containers[0:1]
	}
	return nil
}

// checkContainerStateTransition ensures that no container is trying to transition
// from a terminated to non-terminated state, which is illegal and indicates a
// logical error in the kubelet.
func checkContainerStateTransition(oldStatuses, newStatuses []v1.ContainerStatus, restartPolicy v1.RestartPolicy) error {
	// If we should always restart, containers are allowed to leave the terminated state
	if restartPolicy == v1.RestartPolicyAlways {
		return nil
	}
	for _, oldStatus := range oldStatuses {
		// Skip any container that wasn't terminated
		if oldStatus.State.Terminated == nil {
			continue
		}
		// Skip any container that failed but is allowed to restart
		if oldStatus.State.Terminated.ExitCode != 0 && restartPolicy == v1.RestartPolicyOnFailure {
			continue
		}
		for _, newStatus := range newStatuses {
			if oldStatus.Name == newStatus.Name && newStatus.State.Terminated == nil {
				return fmt.Errorf("terminated container %v attempted illegal transition to non-terminated state", newStatus.Name)
			}
		}
	}
	return nil
}

// updateStatusInternal updates the internal status cache, and queues an update to the api server if
// necessary. Returns whether an update was triggered.
// This method IS NOT THREAD SAFE and must be called from a locked function.
func (m *manager) updateStatusInternal(pod *v1.Pod, status v1.PodStatus, forceUpdate bool) bool {
	var oldStatus v1.PodStatus
	cachedStatus, isCached := m.podStatuses[pod.UID]
	if isCached {
		oldStatus = cachedStatus.status
	} else if mirrorPod, ok := m.podManager.GetMirrorPodByPod(pod); ok {
		oldStatus = mirrorPod.Status
	} else {
		oldStatus = pod.Status
	}

	// Check for illegal state transition in containers
	if err := checkContainerStateTransition(oldStatus.ContainerStatuses, status.ContainerStatuses, pod.Spec.RestartPolicy); err != nil {
		klog.ErrorS(err, "Status update on pod aborted", "pod", klog.KObj(pod))
		return false
	}
	if err := checkContainerStateTransition(oldStatus.InitContainerStatuses, status.InitContainerStatuses, pod.Spec.RestartPolicy); err != nil {
		klog.ErrorS(err, "Status update on pod aborted", "pod", klog.KObj(pod))
		return false
	}

	// Set ContainersReadyCondition.LastTransitionTime.
	updateLastTransitionTime(&status, &oldStatus, v1.ContainersReady)

	// Set ReadyCondition.LastTransitionTime.
	updateLastTransitionTime(&status, &oldStatus, v1.PodReady)

	// Set InitializedCondition.LastTransitionTime.
	updateLastTransitionTime(&status, &oldStatus, v1.PodInitialized)

	// Set PodHasNetwork.LastTransitionTime.
	updateLastTransitionTime(&status, &oldStatus, kubetypes.PodHasNetwork)

	// Set PodScheduledCondition.LastTransitionTime.
	updateLastTransitionTime(&status, &oldStatus, v1.PodScheduled)

	if utilfeature.DefaultFeatureGate.Enabled(features.PodDisruptionConditions) {
		// Set DisruptionTarget.LastTransitionTime.
		updateLastTransitionTime(&status, &oldStatus, v1.DisruptionTarget)
	}

	// ensure that the start time does not change across updates.
	if oldStatus.StartTime != nil && !oldStatus.StartTime.IsZero() {
		status.StartTime = oldStatus.StartTime
	} else if status.StartTime.IsZero() {
		// if the status has no start time, we need to set an initial time
		now := metav1.Now()
		status.StartTime = &now
	}

	normalizeStatus(pod, &status)

	// Perform some more extensive logging of container termination state to assist in
	// debugging production races (generally not needed).
	if klogV := klog.V(5); klogV.Enabled() {
		var containers []string
		for _, s := range append(append([]v1.ContainerStatus(nil), status.InitContainerStatuses...), status.ContainerStatuses...) {
			var current, previous string
			switch {
			case s.State.Running != nil:
				current = "running"
			case s.State.Waiting != nil:
				current = "waiting"
			case s.State.Terminated != nil:
				current = fmt.Sprintf("terminated=%d", s.State.Terminated.ExitCode)
			default:
				current = "unknown"
			}
			switch {
			case s.LastTerminationState.Running != nil:
				previous = "running"
			case s.LastTerminationState.Waiting != nil:
				previous = "waiting"
			case s.LastTerminationState.Terminated != nil:
				previous = fmt.Sprintf("terminated=%d", s.LastTerminationState.Terminated.ExitCode)
			default:
				previous = "<none>"
			}
			containers = append(containers, fmt.Sprintf("(%s state=%s previous=%s)", s.Name, current, previous))
		}
		sort.Strings(containers)
		klogV.InfoS("updateStatusInternal", "version", cachedStatus.version+1, "pod", klog.KObj(pod), "podUID", pod.UID, "containers", strings.Join(containers, " "))
	}

	// The intent here is to prevent concurrent updates to a pod's status from
	// clobbering each other so the phase of a pod progresses monotonically.
	if isCached && isPodStatusByKubeletEqual(&cachedStatus.status, &status) && !forceUpdate {
		klog.V(3).InfoS("Ignoring same status for pod", "pod", klog.KObj(pod), "status", status)
		return false // No new status.
	}

	newStatus := versionedPodStatus{
		status:       status,
		version:      cachedStatus.version + 1,
		podName:      pod.Name,
		podNamespace: pod.Namespace,
	}

	// Multiple status updates can be generated before we update the API server,
	// so we track the time from the first status update until we retire it to
	// the API.
	if cachedStatus.at.IsZero() {
		newStatus.at = time.Now()
	} else {
		newStatus.at = cachedStatus.at
	}

	m.podStatuses[pod.UID] = newStatus

	select {
	case m.podStatusChannel <- podStatusSyncRequest{pod.UID, newStatus}:
		klog.V(5).InfoS("Status Manager: adding pod with new status to podStatusChannel",
			"pod", klog.KObj(pod),
			"podUID", pod.UID,
			"statusVersion", newStatus.version,
			"status", newStatus.status)
		return true
	default:
		// Let the periodic syncBatch handle the update if the channel is full.
		// We can't block, since we hold the mutex lock.
		klog.V(4).InfoS("Skipping the status update for pod for now because the channel is full",
			"pod", klog.KObj(pod),
			"status", status)
		return false
	}
}

// updateLastTransitionTime updates the LastTransitionTime of a pod condition.
func updateLastTransitionTime(status, oldStatus *v1.PodStatus, conditionType v1.PodConditionType) {
	_, condition := podutil.GetPodCondition(status, conditionType)
	if condition == nil {
		return
	}
	// Need to set LastTransitionTime.
	lastTransitionTime := metav1.Now()
	_, oldCondition := podutil.GetPodCondition(oldStatus, conditionType)
	if oldCondition != nil && condition.Status == oldCondition.Status {
		lastTransitionTime = oldCondition.LastTransitionTime
	}
	condition.LastTransitionTime = lastTransitionTime
}

// deletePodStatus simply removes the given pod from the status cache.
func (m *manager) deletePodStatus(uid types.UID) {
	m.podStatusesLock.Lock()
	defer m.podStatusesLock.Unlock()
	delete(m.podStatuses, uid)
	m.podStartupLatencyHelper.DeletePodStartupState(uid)
}

// TODO(filipg): It'd be cleaner if we can do this without signal from user.
func (m *manager) RemoveOrphanedStatuses(podUIDs map[types.UID]bool) {
	m.podStatusesLock.Lock()
	defer m.podStatusesLock.Unlock()
	for key := range m.podStatuses {
		if _, ok := podUIDs[key]; !ok {
			klog.V(5).InfoS("Removing pod from status map.", "podUID", key)
			delete(m.podStatuses, key)
		}
	}
}

// syncBatch syncs pods statuses with the apiserver.
func (m *manager) syncBatch() {
	var updatedStatuses []podStatusSyncRequest
	podToMirror, mirrorToPod := m.podManager.GetUIDTranslations()
	func() { // Critical section
		m.podStatusesLock.RLock()
		defer m.podStatusesLock.RUnlock()

		// Clean up orphaned versions.
		for uid := range m.apiStatusVersions {
			_, hasPod := m.podStatuses[types.UID(uid)]
			_, hasMirror := mirrorToPod[uid]
			if !hasPod && !hasMirror {
				delete(m.apiStatusVersions, uid)
			}
		}

		for uid, status := range m.podStatuses {
			syncedUID := kubetypes.MirrorPodUID(uid)
			if mirrorUID, ok := podToMirror[kubetypes.ResolvedPodUID(uid)]; ok {
				if mirrorUID == "" {
					klog.V(5).InfoS("Static pod does not have a corresponding mirror pod; skipping",
						"podUID", uid,
						"pod", klog.KRef(status.podNamespace, status.podName))
					continue
				}
				syncedUID = mirrorUID
			}
			if m.needsUpdate(types.UID(syncedUID), status) {
				updatedStatuses = append(updatedStatuses, podStatusSyncRequest{uid, status})
			} else if m.needsReconcile(uid, status.status) {
				// Delete the apiStatusVersions here to force an update on the pod status
				// In most cases the deleted apiStatusVersions here should be filled
				// soon after the following syncPod() [If the syncPod() sync an update
				// successfully].
				delete(m.apiStatusVersions, syncedUID)
				updatedStatuses = append(updatedStatuses, podStatusSyncRequest{uid, status})
			}
		}
	}()

	for _, update := range updatedStatuses {
		klog.V(5).InfoS("Status Manager: syncPod in syncbatch", "podUID", update.podUID)
		m.syncPod(update.podUID, update.status)
	}
}

// syncPod syncs the given status with the API server. The caller must not hold the lock.
func (m *manager) syncPod(uid types.UID, status versionedPodStatus) {
	if !m.needsUpdate(uid, status) {
		klog.V(1).InfoS("Status for pod is up-to-date; skipping", "podUID", uid)
		return
	}

	// TODO: make me easier to express from client code
	pod, err := m.kubeClient.CoreV1().Pods(status.podNamespace).Get(context.TODO(), status.podName, metav1.GetOptions{})
	if errors.IsNotFound(err) {
		klog.V(3).InfoS("Pod does not exist on the server",
			"podUID", uid,
			"pod", klog.KRef(status.podNamespace, status.podName))
		// If the Pod is deleted the status will be cleared in
		// RemoveOrphanedStatuses, so we just ignore the update here.
		return
	}
	if err != nil {
		klog.InfoS("Failed to get status for pod",
			"podUID", uid,
			"pod", klog.KRef(status.podNamespace, status.podName),
			"err", err)
		return
	}

	translatedUID := m.podManager.TranslatePodUID(pod.UID)
	// Type convert original uid just for the purpose of comparison.
	if len(translatedUID) > 0 && translatedUID != kubetypes.ResolvedPodUID(uid) {
		klog.V(2).InfoS("Pod was deleted and then recreated, skipping status update",
			"pod", klog.KObj(pod),
			"oldPodUID", uid,
			"podUID", translatedUID)
		m.deletePodStatus(uid)
		return
	}

	mergedStatus := mergePodStatus(pod.Status, status.status, m.podDeletionSafety.PodCouldHaveRunningContainers(pod))

	newPod, patchBytes, unchanged, err := statusutil.PatchPodStatus(context.TODO(), m.kubeClient, pod.Namespace, pod.Name, pod.UID, pod.Status, mergedStatus)
	klog.V(3).InfoS("Patch status for pod", "pod", klog.KObj(pod), "podUID", uid, "patch", string(patchBytes))

	if err != nil {
		klog.InfoS("Failed to update status for pod", "pod", klog.KObj(pod), "err", err)
		return
	}
	if unchanged {
		klog.V(3).InfoS("Status for pod is up-to-date", "pod", klog.KObj(pod), "statusVersion", status.version)
	} else {
		klog.V(3).InfoS("Status for pod updated successfully", "pod", klog.KObj(pod), "statusVersion", status.version, "status", mergedStatus)
		pod = newPod
		// We pass a new object (result of API call which contains updated ResourceVersion)
		m.podStartupLatencyHelper.RecordStatusUpdated(pod)
	}

	// measure how long the status update took to propagate from generation to update on the server
	if status.at.IsZero() {
		klog.V(3).InfoS("Pod had no status time set", "pod", klog.KObj(pod), "podUID", uid, "version", status.version)
	} else {
		duration := time.Now().Sub(status.at).Truncate(time.Millisecond)
		metrics.PodStatusSyncDuration.Observe(duration.Seconds())
	}

	m.apiStatusVersions[kubetypes.MirrorPodUID(pod.UID)] = status.version

	// We don't handle graceful deletion of mirror pods.
	if m.canBeDeleted(pod, status.status) {
		deleteOptions := metav1.DeleteOptions{
			GracePeriodSeconds: new(int64),
			// Use the pod UID as the precondition for deletion to prevent deleting a
			// newly created pod with the same name and namespace.
			Preconditions: metav1.NewUIDPreconditions(string(pod.UID)),
		}
		err = m.kubeClient.CoreV1().Pods(pod.Namespace).Delete(context.TODO(), pod.Name, deleteOptions)
		if err != nil {
			klog.InfoS("Failed to delete status for pod", "pod", klog.KObj(pod), "err", err)
			return
		}
		klog.V(3).InfoS("Pod fully terminated and removed from etcd", "pod", klog.KObj(pod))
		m.deletePodStatus(uid)
	}
}

// needsUpdate returns whether the status is stale for the given pod UID.
// This method is not thread safe, and must only be accessed by the sync thread.
func (m *manager) needsUpdate(uid types.UID, status versionedPodStatus) bool {
	latest, ok := m.apiStatusVersions[kubetypes.MirrorPodUID(uid)]
	if !ok || latest < status.version {
		return true
	}
	pod, ok := m.podManager.GetPodByUID(uid)
	if !ok {
		return false
	}
	return m.canBeDeleted(pod, status.status)
}

func (m *manager) canBeDeleted(pod *v1.Pod, status v1.PodStatus) bool {
	if pod.DeletionTimestamp == nil || kubetypes.IsMirrorPod(pod) {
		return false
	}
	return m.podDeletionSafety.PodResourcesAreReclaimed(pod, status)
}

// needsReconcile compares the given status with the status in the pod manager (which
// in fact comes from apiserver), returns whether the status needs to be reconciled with
// the apiserver. Now when pod status is inconsistent between apiserver and kubelet,
// kubelet should forcibly send an update to reconcile the inconsistence, because kubelet
// should be the source of truth of pod status.
// NOTE(random-liu): It's simpler to pass in mirror pod uid and get mirror pod by uid, but
// now the pod manager only supports getting mirror pod by static pod, so we have to pass
// static pod uid here.
// TODO(random-liu): Simplify the logic when mirror pod manager is added.
func (m *manager) needsReconcile(uid types.UID, status v1.PodStatus) bool {
	// The pod could be a static pod, so we should translate first.
	pod, ok := m.podManager.GetPodByUID(uid)
	if !ok {
		klog.V(4).InfoS("Pod has been deleted, no need to reconcile", "podUID", string(uid))
		return false
	}
	// If the pod is a static pod, we should check its mirror pod, because only status in mirror pod is meaningful to us.
	if kubetypes.IsStaticPod(pod) {
		mirrorPod, ok := m.podManager.GetMirrorPodByPod(pod)
		if !ok {
			klog.V(4).InfoS("Static pod has no corresponding mirror pod, no need to reconcile", "pod", klog.KObj(pod))
			return false
		}
		pod = mirrorPod
	}

	podStatus := pod.Status.DeepCopy()
	normalizeStatus(pod, podStatus)

	if isPodStatusByKubeletEqual(podStatus, &status) {
		// If the status from the source is the same with the cached status,
		// reconcile is not needed. Just return.
		return false
	}
	klog.V(3).InfoS("Pod status is inconsistent with cached status for pod, a reconciliation should be triggered",
		"pod", klog.KObj(pod),
		"statusDiff", diff.ObjectDiff(podStatus, &status))

	return true
}

// normalizeStatus normalizes nanosecond precision timestamps in podStatus
// down to second precision (*RFC339NANO* -> *RFC3339*). This must be done
// before comparing podStatus to the status returned by apiserver because
// apiserver does not support RFC339NANO.
// Related issue #15262/PR #15263 to move apiserver to RFC339NANO is closed.
func normalizeStatus(pod *v1.Pod, status *v1.PodStatus) *v1.PodStatus {
	bytesPerStatus := kubecontainer.MaxPodTerminationMessageLogLength
	if containers := len(pod.Spec.Containers) + len(pod.Spec.InitContainers); containers > 0 {
		bytesPerStatus = bytesPerStatus / containers
	}
	normalizeTimeStamp := func(t *metav1.Time) {
		*t = t.Rfc3339Copy()
	}
	normalizeContainerState := func(c *v1.ContainerState) {
		if c.Running != nil {
			normalizeTimeStamp(&c.Running.StartedAt)
		}
		if c.Terminated != nil {
			normalizeTimeStamp(&c.Terminated.StartedAt)
			normalizeTimeStamp(&c.Terminated.FinishedAt)
			if len(c.Terminated.Message) > bytesPerStatus {
				c.Terminated.Message = c.Terminated.Message[:bytesPerStatus]
			}
		}
	}

	if status.StartTime != nil {
		normalizeTimeStamp(status.StartTime)
	}
	for i := range status.Conditions {
		condition := &status.Conditions[i]
		normalizeTimeStamp(&condition.LastProbeTime)
		normalizeTimeStamp(&condition.LastTransitionTime)
	}

	// update container statuses
	for i := range status.ContainerStatuses {
		cstatus := &status.ContainerStatuses[i]
		normalizeContainerState(&cstatus.State)
		normalizeContainerState(&cstatus.LastTerminationState)
	}
	// Sort the container statuses, so that the order won't affect the result of comparison
	sort.Sort(kubetypes.SortedContainerStatuses(status.ContainerStatuses))

	// update init container statuses
	for i := range status.InitContainerStatuses {
		cstatus := &status.InitContainerStatuses[i]
		normalizeContainerState(&cstatus.State)
		normalizeContainerState(&cstatus.LastTerminationState)
	}
	// Sort the container statuses, so that the order won't affect the result of comparison
	kubetypes.SortInitContainerStatuses(pod, status.InitContainerStatuses)
	return status
}

// mergePodStatus merges oldPodStatus and newPodStatus to preserve where pod conditions
// not owned by kubelet and to ensure terminal phase transition only happens after all
// running containers have terminated. This method does not modify the old status.
func mergePodStatus(oldPodStatus, newPodStatus v1.PodStatus, couldHaveRunningContainers bool) v1.PodStatus {
	podConditions := make([]v1.PodCondition, 0, len(oldPodStatus.Conditions)+len(newPodStatus.Conditions))

	for _, c := range oldPodStatus.Conditions {
		if !kubetypes.PodConditionByKubelet(c.Type) {
			podConditions = append(podConditions, c)
		}
	}

	transitioningToTerminalPhase := !podutil.IsPodPhaseTerminal(oldPodStatus.Phase) && podutil.IsPodPhaseTerminal(newPodStatus.Phase)

	for _, c := range newPodStatus.Conditions {
		if kubetypes.PodConditionByKubelet(c.Type) {
			podConditions = append(podConditions, c)
		} else if kubetypes.PodConditionSharedByKubelet(c.Type) {
			// we replace or append all the "shared by kubelet" conditions
			if c.Type == v1.DisruptionTarget {
				// guard the update of the DisruptionTarget condition with a check to ensure
				// it will only be sent once all containers have terminated and the phase
				// is terminal. This avoids sending an unnecessary patch request to add
				// the condition if the actual status phase transition is delayed.
				if transitioningToTerminalPhase && !couldHaveRunningContainers {
					// update the LastTransitionTime again here because the older transition
					// time set in updateStatusInternal is likely stale as sending of
					// the condition was delayed until all pod's containers have terminated.
					updateLastTransitionTime(&newPodStatus, &oldPodStatus, c.Type)
					if _, c := podutil.GetPodConditionFromList(newPodStatus.Conditions, c.Type); c != nil {
						// for shared conditions we update or append in podConditions
						podConditions = statusutil.ReplaceOrAppendPodCondition(podConditions, c)
					}
				}
			}
		}
	}
	newPodStatus.Conditions = podConditions

	// Delay transitioning a pod to a terminal status unless the pod is actually terminal.
	// The Kubelet should never transition a pod to terminal status that could have running
	// containers and thus actively be leveraging exclusive resources. Note that resources
	// like volumes are reconciled by a subsystem in the Kubelet and will converge if a new
	// pod reuses an exclusive resource (unmount -> free -> mount), which means we do not
	// need wait for those resources to be detached by the Kubelet. In general, resources
	// the Kubelet exclusively owns must be released prior to a pod being reported terminal,
	// while resources that have participanting components above the API use the pod's
	// transition to a terminal phase (or full deletion) to release those resources.
	if transitioningToTerminalPhase {
		if couldHaveRunningContainers {
			newPodStatus.Phase = oldPodStatus.Phase
			newPodStatus.Reason = oldPodStatus.Reason
			newPodStatus.Message = oldPodStatus.Message
		}
	}

	// If the new phase is terminal, explicitly set the ready condition to false for v1.PodReady and v1.ContainersReady.
	// It may take some time for kubelet to reconcile the ready condition, so explicitly set ready conditions to false if the phase is terminal.
	// This is done to ensure kubelet does not report a status update with terminal pod phase and ready=true.
	// See https://issues.k8s.io/108594 for more details.
	if podutil.IsPodPhaseTerminal(newPodStatus.Phase) {
		if podutil.IsPodReadyConditionTrue(newPodStatus) || podutil.IsContainersReadyConditionTrue(newPodStatus) {
			containersReadyCondition := generateContainersReadyConditionForTerminalPhase(newPodStatus.Phase)
			podutil.UpdatePodCondition(&newPodStatus, &containersReadyCondition)

			podReadyCondition := generatePodReadyConditionForTerminalPhase(newPodStatus.Phase)
			podutil.UpdatePodCondition(&newPodStatus, &podReadyCondition)
		}
	}

	return newPodStatus
}

// NeedToReconcilePodReadiness returns if the pod "Ready" condition need to be reconcile
func NeedToReconcilePodReadiness(pod *v1.Pod) bool {
	if len(pod.Spec.ReadinessGates) == 0 {
		return false
	}
	podReadyCondition := GeneratePodReadyCondition(&pod.Spec, pod.Status.Conditions, pod.Status.ContainerStatuses, pod.Status.Phase)
	i, curCondition := podutil.GetPodConditionFromList(pod.Status.Conditions, v1.PodReady)
	// Only reconcile if "Ready" condition is present and Status or Message is not expected
	if i >= 0 && (curCondition.Status != podReadyCondition.Status || curCondition.Message != podReadyCondition.Message) {
		return true
	}
	return false
}
