/*
Copyright 2015 The Kubernetes Authors.
Copyright 2020 Authors of Arktos - file modified.

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.
*/

package prober

import (
	"sync"

	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/client-go/tools/record"
	"k8s.io/component-base/metrics"
	"k8s.io/klog"
	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
	"k8s.io/kubernetes/pkg/kubelet/prober/results"
	"k8s.io/kubernetes/pkg/kubelet/status"
	"k8s.io/kubernetes/pkg/kubelet/util/format"
)

// ProberResults stores the cumulative number of a probe by result as prometheus metrics.
var ProberResults = metrics.NewCounterVec(
	&metrics.CounterOpts{
		Subsystem:      "prober",
		Name:           "probe_total",
		Help:           "Cumulative number of a liveness, readiness or startup probe for a container by result.",
		StabilityLevel: metrics.ALPHA,
	},
	[]string{"probe_type",
		"result",
		"container",
		"pod",
		"namespace",
		"pod_uid"},
)

// Manager manages pod probing. It creates a probe "worker" for every container that specifies a
// probe (AddPod). The worker periodically probes its assigned container and caches the results. The
// manager use the cached probe results to set the appropriate Ready state in the PodStatus when
// requested (UpdatePodStatus). Updating probe parameters is not currently supported.
// TODO: Move liveness probing out of the runtime, to here.
type Manager interface {
	// AddPod creates new probe workers for every container probe. This should be called for every
	// pod created.
	AddPod(pod *v1.Pod)

	// RemovePod handles cleaning up the removed pod state, including terminating probe workers and
	// deleting cached results.
	RemovePod(pod *v1.Pod)

	// CleanupPods handles cleaning up pods which should no longer be running.
	// It takes a map of "desired pods" which should not be cleaned up.
	CleanupPods(desiredPods map[types.UID]sets.Empty)

	// UpdatePodStatus modifies the given PodStatus with the appropriate Ready state for each
	// container based on container running status, cached probe results and worker states.
	UpdatePodStatus(types.UID, *v1.PodStatus)

	// Start starts the Manager sync loops.
	Start()
}

type manager struct {
	// Map of active workers for probes
	workers map[probeKey]*worker
	// Lock for accessing & mutating workers
	workerLock sync.RWMutex

	// The statusManager cache provides pod IP and container IDs for probing.
	statusManager status.Manager

	// readinessManager manages the results of readiness probes
	readinessManager results.Manager

	// livenessManager manages the results of liveness probes
	livenessManager results.Manager

	// prober executes the probe actions.
	prober *prober
}

// NewManager creates a Manager for pod probing.
func NewManager(
	statusManager status.Manager,
	livenessManager results.Manager,
	runner kubecontainer.ContainerCommandRunner,
	refManager *kubecontainer.RefManager,
	recorder record.EventRecorder) Manager {

	prober := newProber(runner, refManager, recorder)
	readinessManager := results.NewManager()
	return &manager{
		statusManager:    statusManager,
		prober:           prober,
		readinessManager: readinessManager,
		livenessManager:  livenessManager,
		workers:          make(map[probeKey]*worker),
	}
}

// Start syncing probe status. This should only be called once.
func (m *manager) Start() {
	// Start syncing readiness.
	go wait.Forever(m.updateReadiness, 0)
}

// Key uniquely identifying container probes
type probeKey struct {
	podUID        types.UID
	containerName string
	probeType     probeType
}

// Type of probe (liveness, readiness or startup)
type probeType int

const (
	liveness probeType = iota
	readiness

	probeResultSuccessful string = "successful"
	probeResultFailed     string = "failed"
	probeResultUnknown    string = "unknown"
)

// For debugging.
func (t probeType) String() string {
	switch t {
	case readiness:
		return "Readiness"
	case liveness:
		return "Liveness"
	default:
		return "UNKNOWN"
	}
}

func (m *manager) AddPod(pod *v1.Pod) {
	m.workerLock.Lock()
	defer m.workerLock.Unlock()

	key := probeKey{podUID: pod.UID}
	for _, c := range pod.Spec.Containers {
		key.containerName = c.Name

		if c.ReadinessProbe != nil {
			key.probeType = readiness
			if _, ok := m.workers[key]; ok {
				klog.Errorf("Readiness probe already exists! %v - %v",
					format.Pod(pod), c.Name)
				return
			}
			w := newWorker(m, readiness, pod, c)
			m.workers[key] = w
			go w.run()
		}

		if c.LivenessProbe != nil {
			key.probeType = liveness
			if _, ok := m.workers[key]; ok {
				klog.Errorf("Liveness probe already exists! %v - %v",
					format.Pod(pod), c.Name)
				return
			}
			w := newWorker(m, liveness, pod, c)
			m.workers[key] = w
			go w.run()
		}
	}
}

func (m *manager) RemovePod(pod *v1.Pod) {
	m.workerLock.RLock()
	defer m.workerLock.RUnlock()

	key := probeKey{podUID: pod.UID}
	for _, c := range pod.Spec.Containers {
		key.containerName = c.Name
		for _, probeType := range [...]probeType{readiness, liveness} {
			key.probeType = probeType
			if worker, ok := m.workers[key]; ok {
				worker.stop()
			}
		}
	}
}

func (m *manager) CleanupPods(desiredPods map[types.UID]sets.Empty) {
	m.workerLock.RLock()
	defer m.workerLock.RUnlock()

	for key, worker := range m.workers {
		if _, ok := desiredPods[key.podUID]; !ok {
			worker.stop()
		}
	}
}

func (m *manager) UpdatePodStatus(podUID types.UID, podStatus *v1.PodStatus) {
	for i, c := range podStatus.ContainerStatuses {
		var ready bool
		if c.State.Running == nil {
			ready = false
		} else if result, ok := m.readinessManager.Get(kubecontainer.ParseContainerID(c.ContainerID)); ok {
			ready = result == results.Success
		} else {
			// The check whether there is a probe which hasn't run yet.
			_, exists := m.getWorker(podUID, c.Name, readiness)
			ready = !exists
		}
		podStatus.ContainerStatuses[i].Ready = ready
	}
	// init containers are ready if they have exited with success or if a readiness probe has
	// succeeded.
	for i, c := range podStatus.InitContainerStatuses {
		var ready bool
		if c.State.Terminated != nil && c.State.Terminated.ExitCode == 0 {
			ready = true
		}
		podStatus.InitContainerStatuses[i].Ready = ready
	}
}

func (m *manager) getWorker(podUID types.UID, containerName string, probeType probeType) (*worker, bool) {
	m.workerLock.RLock()
	defer m.workerLock.RUnlock()
	worker, ok := m.workers[probeKey{podUID, containerName, probeType}]
	return worker, ok
}

// Called by the worker after exiting.
func (m *manager) removeWorker(podUID types.UID, containerName string, probeType probeType) {
	m.workerLock.Lock()
	defer m.workerLock.Unlock()
	delete(m.workers, probeKey{podUID, containerName, probeType})
}

// workerCount returns the total number of probe workers. For testing.
func (m *manager) workerCount() int {
	m.workerLock.RLock()
	defer m.workerLock.RUnlock()
	return len(m.workers)
}

func (m *manager) updateReadiness() {
	update := <-m.readinessManager.Updates()

	ready := update.Result == results.Success
	m.statusManager.SetContainerReadiness(update.PodUID, update.ContainerID, ready)
}
