/*
Copyright 2016 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.
*/

// Package reconciler implements interfaces that attempt to reconcile the
// desired state of the with the actual state of the world by triggering
// actions.
package reconciler

import (
	"time"

	"github.com/golang/glog"
	"k8s.io/kubernetes/pkg/controller/volume/attachdetach/cache"
	"k8s.io/kubernetes/pkg/controller/volume/attachdetach/statusupdater"
	"k8s.io/kubernetes/pkg/util/goroutinemap/exponentialbackoff"
	"k8s.io/kubernetes/pkg/util/wait"
	"k8s.io/kubernetes/pkg/volume/util/nestedpendingoperations"
	"k8s.io/kubernetes/pkg/volume/util/operationexecutor"
)

// Reconciler runs a periodic loop to reconcile the desired state of the with
// the actual state of the world by triggering attach detach operations.
// Note: This is distinct from the Reconciler implemented by the kubelet volume
// manager. This reconciles state for the attach/detach controller. That
// reconciles state for the kubelet volume manager.
type Reconciler interface {
	// Starts running the reconciliation loop which executes periodically, checks
	// if volumes that should be attached are attached and volumes that should
	// be detached are detached. If not, it will trigger attach/detach
	// operations to rectify.
	Run(stopCh <-chan struct{})
}

// NewReconciler returns a new instance of Reconciler that waits loopPeriod
// between successive executions.
// loopPeriod is the amount of time the reconciler loop waits between
// successive executions.
// maxWaitForUnmountDuration is the max amount of time the reconciler will wait
// for the volume to be safely unmounted, after this it will detach the volume
// anyway (to handle crashed/unavailable nodes). If during this time the volume
// becomes used by a new pod, the detach request will be aborted and the timer
// cleared.
func NewReconciler(
	loopPeriod time.Duration,
	maxWaitForUnmountDuration time.Duration,
	desiredStateOfWorld cache.DesiredStateOfWorld,
	actualStateOfWorld cache.ActualStateOfWorld,
	attacherDetacher operationexecutor.OperationExecutor,
	nodeStatusUpdater statusupdater.NodeStatusUpdater) Reconciler {
	return &reconciler{
		loopPeriod:                loopPeriod,
		maxWaitForUnmountDuration: maxWaitForUnmountDuration,
		desiredStateOfWorld:       desiredStateOfWorld,
		actualStateOfWorld:        actualStateOfWorld,
		attacherDetacher:          attacherDetacher,
		nodeStatusUpdater:         nodeStatusUpdater,
	}
}

type reconciler struct {
	loopPeriod                time.Duration
	maxWaitForUnmountDuration time.Duration
	desiredStateOfWorld       cache.DesiredStateOfWorld
	actualStateOfWorld        cache.ActualStateOfWorld
	attacherDetacher          operationexecutor.OperationExecutor
	nodeStatusUpdater         statusupdater.NodeStatusUpdater
}

func (rc *reconciler) Run(stopCh <-chan struct{}) {
	wait.Until(rc.reconciliationLoopFunc(), rc.loopPeriod, stopCh)
}

func (rc *reconciler) reconciliationLoopFunc() func() {
	return func() {
		// Detaches are triggered before attaches so that volumes referenced by
		// pods that are rescheduled to a different node are detached first.

		// Ensure volumes that should be detached are detached.
		for _, attachedVolume := range rc.actualStateOfWorld.GetAttachedVolumes() {
			if !rc.desiredStateOfWorld.VolumeExists(
				attachedVolume.VolumeName, attachedVolume.NodeName) {
				// Volume exists in actual state of world but not desired

				// Mark desire to detach
				timeElapsed, err := rc.actualStateOfWorld.MarkDesireToDetach(attachedVolume.VolumeName, attachedVolume.NodeName)
				if err != nil {
					glog.Errorf("Unexpected error actualStateOfWorld.MarkDesireToDetach(): %v", err)
				}

				// Update Node Status to indicate volume is no longer safe to mount.
				err = rc.nodeStatusUpdater.UpdateNodeStatuses()
				if err != nil {
					// Skip detaching this volume if unable to update node status
					glog.Infof("UpdateNodeStatuses failed with: %v", err)
					continue
				}

				if !attachedVolume.MountedByNode {
					glog.V(5).Infof("Attempting to start DetachVolume for volume %q from node %q", attachedVolume.VolumeName, attachedVolume.NodeName)
					err := rc.attacherDetacher.DetachVolume(attachedVolume.AttachedVolume, true /* verifySafeToDetach */, rc.actualStateOfWorld)
					if err == nil {
						glog.Infof("Started DetachVolume for volume %q from node %q", attachedVolume.VolumeName, attachedVolume.NodeName)
					}
					if err != nil &&
						!nestedpendingoperations.IsAlreadyExists(err) &&
						!exponentialbackoff.IsExponentialBackoff(err) {
						// Ignore nestedpendingoperations.IsAlreadyExists && exponentialbackoff.IsExponentialBackoff errors, they are expected.
						// Log all other errors.
						glog.Errorf(
							"operationExecutor.DetachVolume failed to start for volume %q (spec.Name: %q) from node %q with err: %v",
							attachedVolume.VolumeName,
							attachedVolume.VolumeSpec.Name(),
							attachedVolume.NodeName,
							err)
					}
				} else {
					// If volume is not safe to detach (is mounted) wait a max amount of time before detaching anyway.
					if timeElapsed > rc.maxWaitForUnmountDuration {
						glog.V(5).Infof("Attempting to start DetachVolume for volume %q from node %q. Volume is not safe to detach, but maxWaitForUnmountDuration expired.", attachedVolume.VolumeName, attachedVolume.NodeName)
						err := rc.attacherDetacher.DetachVolume(attachedVolume.AttachedVolume, false /* verifySafeToDetach */, rc.actualStateOfWorld)
						if err == nil {
							glog.Infof("Started DetachVolume for volume %q from node %q due to maxWaitForUnmountDuration expiry.", attachedVolume.VolumeName, attachedVolume.NodeName)
						}
						if err != nil &&
							!nestedpendingoperations.IsAlreadyExists(err) &&
							!exponentialbackoff.IsExponentialBackoff(err) {
							// Ignore nestedpendingoperations.IsAlreadyExists && exponentialbackoff.IsExponentialBackoff errors, they are expected.
							// Log all other errors.
							glog.Errorf(
								"operationExecutor.DetachVolume failed to start (maxWaitForUnmountDuration expiry) for volume %q (spec.Name: %q) from node %q with err: %v",
								attachedVolume.VolumeName,
								attachedVolume.VolumeSpec.Name(),
								attachedVolume.NodeName,
								err)
						}
					}
				}
			}
		}

		// Ensure volumes that should be attached are attached.
		for _, volumeToAttach := range rc.desiredStateOfWorld.GetVolumesToAttach() {
			if rc.actualStateOfWorld.VolumeNodeExists(
				volumeToAttach.VolumeName, volumeToAttach.NodeName) {
				// Volume/Node exists, touch it to reset detachRequestedTime
				glog.V(12).Infof("Volume %q/Node %q is attached--touching.", volumeToAttach.VolumeName, volumeToAttach.NodeName)
				_, err := rc.actualStateOfWorld.AddVolumeNode(
					volumeToAttach.VolumeSpec, volumeToAttach.NodeName, "" /* devicePath */)
				if err != nil {
					glog.Errorf("Unexpected error on actualStateOfWorld.AddVolumeNode(): %v", err)
				}
			} else {
				// Volume/Node doesn't exist, spawn a goroutine to attach it
				glog.V(5).Infof("Attempting to start AttachVolume for volume %q to node %q", volumeToAttach.VolumeName, volumeToAttach.NodeName)
				err := rc.attacherDetacher.AttachVolume(volumeToAttach.VolumeToAttach, rc.actualStateOfWorld)
				if err == nil {
					glog.Infof("Started AttachVolume for volume %q to node %q", volumeToAttach.VolumeName, volumeToAttach.NodeName)
				}
				if err != nil &&
					!nestedpendingoperations.IsAlreadyExists(err) &&
					!exponentialbackoff.IsExponentialBackoff(err) {
					// Ignore nestedpendingoperations.IsAlreadyExists && exponentialbackoff.IsExponentialBackoff errors, they are expected.
					// Log all other errors.
					glog.Errorf(
						"operationExecutor.AttachVolume failed to start for volume %q (spec.Name: %q) to node %q with err: %v",
						volumeToAttach.VolumeName,
						volumeToAttach.VolumeSpec.Name(),
						volumeToAttach.NodeName,
						err)
				}
			}
		}

		// Update Node Status
		err := rc.nodeStatusUpdater.UpdateNodeStatuses()
		if err != nil {
			glog.Infof("UpdateNodeStatuses failed with: %v", err)
		}
	}
}