// Copyright 2014 Google Inc. All Rights Reserved.
//
// 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.

// Manager of cAdvisor-monitored containers.
package manager

import (
	"flag"
	"fmt"
	"path"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/docker/libcontainer/cgroups"
	"github.com/golang/glog"
	"github.com/google/cadvisor/collector"
	"github.com/google/cadvisor/container"
	"github.com/google/cadvisor/container/docker"
	"github.com/google/cadvisor/container/raw"
	"github.com/google/cadvisor/events"
	"github.com/google/cadvisor/fs"
	info "github.com/google/cadvisor/info/v1"
	"github.com/google/cadvisor/info/v2"
	"github.com/google/cadvisor/storage/memory"
	"github.com/google/cadvisor/utils/cpuload"
	"github.com/google/cadvisor/utils/oomparser"
	"github.com/google/cadvisor/utils/sysfs"
)

var globalHousekeepingInterval = flag.Duration("global_housekeeping_interval", 1*time.Minute, "Interval between global housekeepings")
var logCadvisorUsage = flag.Bool("log_cadvisor_usage", false, "Whether to log the usage of the cAdvisor container")
var enableLoadReader = flag.Bool("enable_load_reader", false, "Whether to enable cpu load reader")
var eventStorageAgeLimit = flag.String("event_storage_age_limit", "default=24h", "Max length of time for which to store events (per type). Value is a comma separated list of key values, where the keys are event types (e.g.: creation, oom) or \"default\" and the value is a duration. Default is applied to all non-specified event types")
var eventStorageEventLimit = flag.String("event_storage_event_limit", "default=100000", "Max number of events to store (per type). Value is a comma separated list of key values, where the keys are event types (e.g.: creation, oom) or \"default\" and the value is an integer. Default is applied to all non-specified event types")

// The Manager interface defines operations for starting a manager and getting
// container and machine information.
type Manager interface {
	// Start the manager.
	Start() error

	// Stops the manager.
	Stop() error

	// Get information about a container.
	GetContainerInfo(containerName string, query *info.ContainerInfoRequest) (*info.ContainerInfo, error)

	// Get information about all subcontainers of the specified container (includes self).
	SubcontainersInfo(containerName string, query *info.ContainerInfoRequest) ([]*info.ContainerInfo, error)

	// Gets all the Docker containers. Return is a map from full container name to ContainerInfo.
	AllDockerContainers(query *info.ContainerInfoRequest) (map[string]info.ContainerInfo, error)

	// Gets information about a specific Docker container. The specified name is within the Docker namespace.
	DockerContainer(dockerName string, query *info.ContainerInfoRequest) (info.ContainerInfo, error)

	// Gets spec for all containers based on request options.
	GetContainerSpec(containerName string, options v2.RequestOptions) (map[string]v2.ContainerSpec, error)

	// Gets summary stats for all containers based on request options.
	GetDerivedStats(containerName string, options v2.RequestOptions) (map[string]v2.DerivedStats, error)

	// Get info for all requested containers based on the request options.
	GetRequestedContainersInfo(containerName string, options v2.RequestOptions) (map[string]*info.ContainerInfo, error)

	// Returns true if the named container exists.
	Exists(containerName string) bool

	// Get information about the machine.
	GetMachineInfo() (*info.MachineInfo, error)

	// Get version information about different components we depend on.
	GetVersionInfo() (*info.VersionInfo, error)

	// Get filesystem information for a given label.
	// Returns information for all global filesystems if label is empty.
	GetFsInfo(label string) ([]v2.FsInfo, error)

	// Get events streamed through passedChannel that fit the request.
	WatchForEvents(request *events.Request) (*events.EventChannel, error)

	// Get past events that have been detected and that fit the request.
	GetPastEvents(request *events.Request) ([]*info.Event, error)

	CloseEventChannel(watch_id int)
}

// New takes a memory storage and returns a new manager.
func New(memoryStorage *memory.InMemoryStorage, sysfs sysfs.SysFs) (Manager, error) {
	if memoryStorage == nil {
		return nil, fmt.Errorf("manager requires memory storage")
	}

	// Detect the container we are running on.
	selfContainer, err := cgroups.GetThisCgroupDir("cpu")
	if err != nil {
		return nil, err
	}
	glog.Infof("cAdvisor running in container: %q", selfContainer)

	context := fs.Context{DockerRoot: docker.RootDir()}
	fsInfo, err := fs.NewFsInfo(context)
	if err != nil {
		return nil, err
	}
	newManager := &manager{
		containers:        make(map[namespacedContainerName]*containerData),
		quitChannels:      make([]chan error, 0, 2),
		memoryStorage:     memoryStorage,
		fsInfo:            fsInfo,
		cadvisorContainer: selfContainer,
		startupTime:       time.Now(),
	}

	machineInfo, err := getMachineInfo(sysfs, fsInfo)
	if err != nil {
		return nil, err
	}
	newManager.machineInfo = *machineInfo
	glog.Infof("Machine: %+v", newManager.machineInfo)

	versionInfo, err := getVersionInfo()
	if err != nil {
		return nil, err
	}
	newManager.versionInfo = *versionInfo
	glog.Infof("Version: %+v", newManager.versionInfo)

	newManager.eventHandler = events.NewEventManager(parseEventsStoragePolicy())

	// Register Docker container factory.
	err = docker.Register(newManager, fsInfo)
	if err != nil {
		glog.Errorf("Docker container factory registration failed: %v.", err)
	}

	// Register the raw driver.
	err = raw.Register(newManager, fsInfo)
	if err != nil {
		glog.Errorf("Registration of the raw container factory failed: %v", err)
	}

	return newManager, nil
}

// A namespaced container name.
type namespacedContainerName struct {
	// The namespace of the container. Can be empty for the root namespace.
	Namespace string

	// The name of the container in this namespace.
	Name string
}

type manager struct {
	containers             map[namespacedContainerName]*containerData
	containersLock         sync.RWMutex
	memoryStorage          *memory.InMemoryStorage
	fsInfo                 fs.FsInfo
	machineInfo            info.MachineInfo
	versionInfo            info.VersionInfo
	quitChannels           []chan error
	cadvisorContainer      string
	dockerContainersRegexp *regexp.Regexp
	loadReader             cpuload.CpuLoadReader
	eventHandler           events.EventManager
	startupTime            time.Time
}

// Start the container manager.
func (self *manager) Start() error {

	if *enableLoadReader {
		// Create cpu load reader.
		cpuLoadReader, err := cpuload.New()
		if err != nil {
			// TODO(rjnagal): Promote to warning once we support cpu load inside namespaces.
			glog.Infof("Could not initialize cpu load reader: %s", err)
		} else {
			err = cpuLoadReader.Start()
			if err != nil {
				glog.Warning("Could not start cpu load stat collector: %s", err)
			} else {
				self.loadReader = cpuLoadReader
			}
		}
	}

	// Watch for OOMs.
	err := self.watchForNewOoms()
	if err != nil {
		glog.Errorf("Failed to start OOM watcher, will not get OOM events: %v", err)
	}

	// If there are no factories, don't start any housekeeping and serve the information we do have.
	if !container.HasFactories() {
		return nil
	}

	// Create root and then recover all containers.
	err = self.createContainer("/")
	if err != nil {
		return err
	}
	glog.Infof("Starting recovery of all containers")
	err = self.detectSubcontainers("/")
	if err != nil {
		return err
	}
	glog.Infof("Recovery completed")

	// Watch for new container.
	quitWatcher := make(chan error)
	err = self.watchForNewContainers(quitWatcher)
	if err != nil {
		return err
	}
	self.quitChannels = append(self.quitChannels, quitWatcher)

	// Look for new containers in the main housekeeping thread.
	quitGlobalHousekeeping := make(chan error)
	self.quitChannels = append(self.quitChannels, quitGlobalHousekeeping)
	go self.globalHousekeeping(quitGlobalHousekeeping)

	return nil
}

func (self *manager) Stop() error {
	// Stop and wait on all quit channels.
	for i, c := range self.quitChannels {
		// Send the exit signal and wait on the thread to exit (by closing the channel).
		c <- nil
		err := <-c
		if err != nil {
			// Remove the channels that quit successfully.
			self.quitChannels = self.quitChannels[i:]
			return err
		}
	}
	self.quitChannels = make([]chan error, 0, 2)
	if self.loadReader != nil {
		self.loadReader.Stop()
		self.loadReader = nil
	}
	return nil
}

func (self *manager) globalHousekeeping(quit chan error) {
	// Long housekeeping is either 100ms or half of the housekeeping interval.
	longHousekeeping := 100 * time.Millisecond
	if *globalHousekeepingInterval/2 < longHousekeeping {
		longHousekeeping = *globalHousekeepingInterval / 2
	}

	ticker := time.Tick(*globalHousekeepingInterval)
	for {
		select {
		case t := <-ticker:
			start := time.Now()

			// Check for new containers.
			err := self.detectSubcontainers("/")
			if err != nil {
				glog.Errorf("Failed to detect containers: %s", err)
			}

			// Log if housekeeping took too long.
			duration := time.Since(start)
			if duration >= longHousekeeping {
				glog.V(3).Infof("Global Housekeeping(%d) took %s", t.Unix(), duration)
			}
		case <-quit:
			// Quit if asked to do so.
			quit <- nil
			glog.Infof("Exiting global housekeeping thread")
			return
		}
	}
}

func (self *manager) getContainerData(containerName string) (*containerData, error) {
	var cont *containerData
	var ok bool
	func() {
		self.containersLock.RLock()
		defer self.containersLock.RUnlock()

		// Ensure we have the container.
		cont, ok = self.containers[namespacedContainerName{
			Name: containerName,
		}]
	}()
	if !ok {
		return nil, fmt.Errorf("unknown container %q", containerName)
	}
	return cont, nil
}

func (self *manager) GetDerivedStats(containerName string, options v2.RequestOptions) (map[string]v2.DerivedStats, error) {
	conts, err := self.getRequestedContainers(containerName, options)
	if err != nil {
		return nil, err
	}
	stats := make(map[string]v2.DerivedStats)
	for name, cont := range conts {
		d, err := cont.DerivedStats()
		if err != nil {
			return nil, err
		}
		stats[name] = d
	}
	return stats, nil
}

func (self *manager) GetContainerSpec(containerName string, options v2.RequestOptions) (map[string]v2.ContainerSpec, error) {
	conts, err := self.getRequestedContainers(containerName, options)
	if err != nil {
		return nil, err
	}
	specs := make(map[string]v2.ContainerSpec)
	for name, cont := range conts {
		cinfo, err := cont.GetInfo()
		if err != nil {
			return nil, err
		}
		spec := self.getV2Spec(cinfo)
		specs[name] = spec
	}
	return specs, nil
}

// Get V2 container spec from v1 container info.
func (self *manager) getV2Spec(cinfo *containerInfo) v2.ContainerSpec {
	specV1 := self.getAdjustedSpec(cinfo)
	specV2 := v2.ContainerSpec{
		CreationTime: specV1.CreationTime,
		HasCpu:       specV1.HasCpu,
		HasMemory:    specV1.HasMemory,
	}
	if specV1.HasCpu {
		specV2.Cpu.Limit = specV1.Cpu.Limit
		specV2.Cpu.MaxLimit = specV1.Cpu.MaxLimit
		specV2.Cpu.Mask = specV1.Cpu.Mask
	}
	if specV1.HasMemory {
		specV2.Memory.Limit = specV1.Memory.Limit
		specV2.Memory.Reservation = specV1.Memory.Reservation
		specV2.Memory.SwapLimit = specV1.Memory.SwapLimit
	}
	specV2.Aliases = cinfo.Aliases
	specV2.Namespace = cinfo.Namespace
	return specV2
}

func (self *manager) getAdjustedSpec(cinfo *containerInfo) info.ContainerSpec {
	spec := cinfo.Spec

	// Set default value to an actual value
	if spec.HasMemory {
		// Memory.Limit is 0 means there's no limit
		if spec.Memory.Limit == 0 {
			spec.Memory.Limit = uint64(self.machineInfo.MemoryCapacity)
		}
	}
	return spec
}

// Get a container by name.
func (self *manager) GetContainerInfo(containerName string, query *info.ContainerInfoRequest) (*info.ContainerInfo, error) {
	cont, err := self.getContainerData(containerName)
	if err != nil {
		return nil, err
	}
	return self.containerDataToContainerInfo(cont, query)
}

func (self *manager) containerDataToContainerInfo(cont *containerData, query *info.ContainerInfoRequest) (*info.ContainerInfo, error) {
	// Get the info from the container.
	cinfo, err := cont.GetInfo()
	if err != nil {
		return nil, err
	}

	stats, err := self.memoryStorage.RecentStats(cinfo.Name, query.Start, query.End, query.NumStats)
	if err != nil {
		return nil, err
	}

	// Make a copy of the info for the user.
	ret := &info.ContainerInfo{
		ContainerReference: cinfo.ContainerReference,
		Subcontainers:      cinfo.Subcontainers,
		Spec:               self.getAdjustedSpec(cinfo),
		Stats:              stats,
	}
	return ret, nil
}

func (self *manager) getContainer(containerName string) (*containerData, error) {
	self.containersLock.RLock()
	defer self.containersLock.RUnlock()
	cont, ok := self.containers[namespacedContainerName{Name: containerName}]
	if !ok {
		return nil, fmt.Errorf("unknown container %q", containerName)
	}
	return cont, nil
}

func (self *manager) getSubcontainers(containerName string) map[string]*containerData {
	self.containersLock.RLock()
	defer self.containersLock.RUnlock()
	containersMap := make(map[string]*containerData, len(self.containers))

	// Get all the unique subcontainers of the specified container
	matchedName := path.Join(containerName, "/")
	for i := range self.containers {
		name := self.containers[i].info.Name
		if name == containerName || strings.HasPrefix(name, matchedName) {
			containersMap[self.containers[i].info.Name] = self.containers[i]
		}
	}
	return containersMap
}

func (self *manager) SubcontainersInfo(containerName string, query *info.ContainerInfoRequest) ([]*info.ContainerInfo, error) {
	containersMap := self.getSubcontainers(containerName)

	containers := make([]*containerData, 0, len(containersMap))
	for _, cont := range containersMap {
		containers = append(containers, cont)
	}
	return self.containerDataSliceToContainerInfoSlice(containers, query)
}

func (self *manager) getAllDockerContainers() map[string]*containerData {
	self.containersLock.RLock()
	defer self.containersLock.RUnlock()
	containers := make(map[string]*containerData, len(self.containers))

	// Get containers in the Docker namespace.
	for name, cont := range self.containers {
		if name.Namespace == docker.DockerNamespace {
			containers[cont.info.Name] = cont
		}
	}
	return containers
}

func (self *manager) AllDockerContainers(query *info.ContainerInfoRequest) (map[string]info.ContainerInfo, error) {
	containers := self.getAllDockerContainers()

	output := make(map[string]info.ContainerInfo, len(containers))
	for name, cont := range containers {
		inf, err := self.containerDataToContainerInfo(cont, query)
		if err != nil {
			return nil, err
		}
		output[name] = *inf
	}
	return output, nil
}

func (self *manager) getDockerContainer(containerName string) (*containerData, error) {
	self.containersLock.RLock()
	defer self.containersLock.RUnlock()

	// Check for the container in the Docker container namespace.
	cont, ok := self.containers[namespacedContainerName{
		Namespace: docker.DockerNamespace,
		Name:      containerName,
	}]
	if !ok {
		return nil, fmt.Errorf("unable to find Docker container %q", containerName)
	}
	return cont, nil
}

func (self *manager) DockerContainer(containerName string, query *info.ContainerInfoRequest) (info.ContainerInfo, error) {
	container, err := self.getDockerContainer(containerName)
	if err != nil {
		return info.ContainerInfo{}, err
	}

	inf, err := self.containerDataToContainerInfo(container, query)
	if err != nil {
		return info.ContainerInfo{}, err
	}
	return *inf, nil
}

func (self *manager) containerDataSliceToContainerInfoSlice(containers []*containerData, query *info.ContainerInfoRequest) ([]*info.ContainerInfo, error) {
	if len(containers) == 0 {
		return nil, fmt.Errorf("no containers found")
	}

	// Get the info for each container.
	output := make([]*info.ContainerInfo, 0, len(containers))
	for i := range containers {
		cinfo, err := self.containerDataToContainerInfo(containers[i], query)
		if err != nil {
			// Skip containers with errors, we try to degrade gracefully.
			continue
		}
		output = append(output, cinfo)
	}

	return output, nil
}

func (self *manager) GetRequestedContainersInfo(containerName string, options v2.RequestOptions) (map[string]*info.ContainerInfo, error) {
	containers, err := self.getRequestedContainers(containerName, options)
	if err != nil {
		return nil, err
	}
	containersMap := make(map[string]*info.ContainerInfo)
	query := info.ContainerInfoRequest{
		NumStats: options.Count,
	}
	for name, data := range containers {
		info, err := self.containerDataToContainerInfo(data, &query)
		if err != nil {
			// Skip containers with errors, we try to degrade gracefully.
			continue
		}
		containersMap[name] = info
	}
	return containersMap, nil
}

func (self *manager) getRequestedContainers(containerName string, options v2.RequestOptions) (map[string]*containerData, error) {
	containersMap := make(map[string]*containerData)
	switch options.IdType {
	case v2.TypeName:
		if options.Recursive == false {
			cont, err := self.getContainer(containerName)
			if err != nil {
				return containersMap, err
			}
			containersMap[cont.info.Name] = cont
		} else {
			containersMap = self.getSubcontainers(containerName)
			if len(containersMap) == 0 {
				return containersMap, fmt.Errorf("unknown container: %q", containerName)
			}
		}
	case v2.TypeDocker:
		if options.Recursive == false {
			containerName = strings.TrimPrefix(containerName, "/")
			cont, err := self.getDockerContainer(containerName)
			if err != nil {
				return containersMap, err
			}
			containersMap[cont.info.Name] = cont
		} else {
			if containerName != "/" {
				return containersMap, fmt.Errorf("invalid request for docker container %q with subcontainers", containerName)
			}
			containersMap = self.getAllDockerContainers()
		}
	default:
		return containersMap, fmt.Errorf("invalid request type %q", options.IdType)
	}
	return containersMap, nil
}

func (self *manager) GetFsInfo(label string) ([]v2.FsInfo, error) {
	var empty time.Time
	// Get latest data from filesystems hanging off root container.
	stats, err := self.memoryStorage.RecentStats("/", empty, empty, 1)
	if err != nil {
		return nil, err
	}
	dev := ""
	if len(label) != 0 {
		dev, err = self.fsInfo.GetDeviceForLabel(label)
		if err != nil {
			return nil, err
		}
	}
	fsInfo := []v2.FsInfo{}
	for _, fs := range stats[0].Filesystem {
		if len(label) != 0 && fs.Device != dev {
			continue
		}
		mountpoint, err := self.fsInfo.GetMountpointForDevice(fs.Device)
		if err != nil {
			return nil, err
		}
		labels, err := self.fsInfo.GetLabelsForDevice(fs.Device)
		if err != nil {
			return nil, err
		}
		fi := v2.FsInfo{
			Device:     fs.Device,
			Mountpoint: mountpoint,
			Capacity:   fs.Limit,
			Usage:      fs.Usage,
			Labels:     labels,
		}
		fsInfo = append(fsInfo, fi)
	}
	return fsInfo, nil
}

func (m *manager) GetMachineInfo() (*info.MachineInfo, error) {
	// Copy and return the MachineInfo.
	return &m.machineInfo, nil
}

func (m *manager) GetVersionInfo() (*info.VersionInfo, error) {
	return &m.versionInfo, nil
}

func (m *manager) Exists(containerName string) bool {
	m.containersLock.Lock()
	defer m.containersLock.Unlock()

	namespacedName := namespacedContainerName{
		Name: containerName,
	}

	_, ok := m.containers[namespacedName]
	if ok {
		return true
	}
	return false
}

// Create a container.
func (m *manager) createContainer(containerName string) error {
	handler, accept, err := container.NewContainerHandler(containerName)
	if err != nil {
		return err
	}
	if !accept {
		// ignoring this container.
		glog.V(4).Infof("ignoring container %q", containerName)
		return nil
	}
	// TODO(vmarmol): Register collectors.
	collectorManager, err := collector.NewCollectorManager()
	if err != nil {
		return err
	}
	logUsage := *logCadvisorUsage && containerName == m.cadvisorContainer
	cont, err := newContainerData(containerName, m.memoryStorage, handler, m.loadReader, logUsage, collectorManager)
	if err != nil {
		return err
	}

	// Add to the containers map.
	alreadyExists := func() bool {
		m.containersLock.Lock()
		defer m.containersLock.Unlock()

		namespacedName := namespacedContainerName{
			Name: containerName,
		}

		// Check that the container didn't already exist.
		_, ok := m.containers[namespacedName]
		if ok {
			return true
		}

		// Add the container name and all its aliases. The aliases must be within the namespace of the factory.
		m.containers[namespacedName] = cont
		for _, alias := range cont.info.Aliases {
			m.containers[namespacedContainerName{
				Namespace: cont.info.Namespace,
				Name:      alias,
			}] = cont
		}

		return false
	}()
	if alreadyExists {
		return nil
	}
	glog.V(3).Infof("Added container: %q (aliases: %v, namespace: %q)", containerName, cont.info.Aliases, cont.info.Namespace)

	contSpec, err := cont.handler.GetSpec()
	if err != nil {
		return err
	}

	contRef, err := cont.handler.ContainerReference()
	if err != nil {
		return err
	}

	newEvent := &info.Event{
		ContainerName: contRef.Name,
		Timestamp:     contSpec.CreationTime,
		EventType:     info.EventContainerCreation,
	}
	err = m.eventHandler.AddEvent(newEvent)
	if err != nil {
		return err
	}

	// Start the container's housekeeping.
	cont.Start()

	return nil
}

func (m *manager) destroyContainer(containerName string) error {
	m.containersLock.Lock()
	defer m.containersLock.Unlock()

	namespacedName := namespacedContainerName{
		Name: containerName,
	}
	cont, ok := m.containers[namespacedName]
	if !ok {
		// Already destroyed, done.
		return nil
	}

	// Tell the container to stop.
	err := cont.Stop()
	if err != nil {
		return err
	}

	// Remove the container from our records (and all its aliases).
	delete(m.containers, namespacedName)
	for _, alias := range cont.info.Aliases {
		delete(m.containers, namespacedContainerName{
			Namespace: cont.info.Namespace,
			Name:      alias,
		})
	}
	glog.V(3).Infof("Destroyed container: %q (aliases: %v, namespace: %q)", containerName, cont.info.Aliases, cont.info.Namespace)

	contRef, err := cont.handler.ContainerReference()
	if err != nil {
		return err
	}

	newEvent := &info.Event{
		ContainerName: contRef.Name,
		Timestamp:     time.Now(),
		EventType:     info.EventContainerDeletion,
	}
	err = m.eventHandler.AddEvent(newEvent)
	if err != nil {
		return err
	}
	return nil
}

// Detect all containers that have been added or deleted from the specified container.
func (m *manager) getContainersDiff(containerName string) (added []info.ContainerReference, removed []info.ContainerReference, err error) {
	m.containersLock.RLock()
	defer m.containersLock.RUnlock()

	// Get all subcontainers recursively.
	cont, ok := m.containers[namespacedContainerName{
		Name: containerName,
	}]
	if !ok {
		return nil, nil, fmt.Errorf("failed to find container %q while checking for new containers", containerName)
	}
	allContainers, err := cont.handler.ListContainers(container.ListRecursive)
	if err != nil {
		return nil, nil, err
	}
	allContainers = append(allContainers, info.ContainerReference{Name: containerName})

	// Determine which were added and which were removed.
	allContainersSet := make(map[string]*containerData)
	for name, d := range m.containers {
		// Only add the canonical name.
		if d.info.Name == name.Name {
			allContainersSet[name.Name] = d
		}
	}

	// Added containers
	for _, c := range allContainers {
		delete(allContainersSet, c.Name)
		_, ok := m.containers[namespacedContainerName{
			Name: c.Name,
		}]
		if !ok {
			added = append(added, c)
		}
	}

	// Removed ones are no longer in the container listing.
	for _, d := range allContainersSet {
		removed = append(removed, d.info.ContainerReference)
	}

	return
}

// Detect the existing subcontainers and reflect the setup here.
func (m *manager) detectSubcontainers(containerName string) error {
	added, removed, err := m.getContainersDiff(containerName)
	if err != nil {
		return err
	}

	// Add the new containers.
	for _, cont := range added {
		err = m.createContainer(cont.Name)
		if err != nil {
			glog.Errorf("Failed to create existing container: %s: %s", cont.Name, err)
		}
	}

	// Remove the old containers.
	for _, cont := range removed {
		err = m.destroyContainer(cont.Name)
		if err != nil {
			glog.Errorf("Failed to destroy existing container: %s: %s", cont.Name, err)
		}
	}

	return nil
}

// Watches for new containers started in the system. Runs forever unless there is a setup error.
func (self *manager) watchForNewContainers(quit chan error) error {
	var root *containerData
	var ok bool
	func() {
		self.containersLock.RLock()
		defer self.containersLock.RUnlock()
		root, ok = self.containers[namespacedContainerName{
			Name: "/",
		}]
	}()
	if !ok {
		return fmt.Errorf("root container does not exist when watching for new containers")
	}

	// Register for new subcontainers.
	eventsChannel := make(chan container.SubcontainerEvent, 16)
	err := root.handler.WatchSubcontainers(eventsChannel)
	if err != nil {
		return err
	}

	// There is a race between starting the watch and new container creation so we do a detection before we read new containers.
	err = self.detectSubcontainers("/")
	if err != nil {
		return err
	}

	// Listen to events from the container handler.
	go func() {
		for {
			select {
			case event := <-eventsChannel:
				switch {
				case event.EventType == container.SubcontainerAdd:
					err = self.createContainer(event.Name)
				case event.EventType == container.SubcontainerDelete:
					err = self.destroyContainer(event.Name)
				}
				if err != nil {
					glog.Warningf("Failed to process watch event: %v", err)
				}
			case <-quit:
				// Stop processing events if asked to quit.
				err := root.handler.StopWatchingSubcontainers()
				quit <- err
				if err == nil {
					glog.Infof("Exiting thread watching subcontainers")
					return
				}
			}
		}
	}()
	return nil
}

func (self *manager) watchForNewOoms() error {
	glog.Infof("Started watching for new ooms in manager")
	outStream := make(chan *oomparser.OomInstance, 10)
	oomLog, err := oomparser.New()
	if err != nil {
		return err
	}
	go oomLog.StreamOoms(outStream)

	go func() {
		for oomInstance := range outStream {
			// Surface OOM and OOM kill events.
			newEvent := &info.Event{
				ContainerName: oomInstance.ContainerName,
				Timestamp:     oomInstance.TimeOfDeath,
				EventType:     info.EventOom,
			}
			err := self.eventHandler.AddEvent(newEvent)
			if err != nil {
				glog.Errorf("failed to add OOM event for %q: %v", oomInstance.ContainerName, err)
			}
			glog.V(3).Infof("Created an OOM event in container %q at %v", oomInstance.ContainerName, oomInstance.TimeOfDeath)

			newEvent = &info.Event{
				ContainerName: oomInstance.VictimContainerName,
				Timestamp:     oomInstance.TimeOfDeath,
				EventType:     info.EventOomKill,
				EventData: info.EventData{
					OomKill: &info.OomKillEventData{
						Pid:         oomInstance.Pid,
						ProcessName: oomInstance.ProcessName,
					},
				},
			}
			err = self.eventHandler.AddEvent(newEvent)
			if err != nil {
				glog.Errorf("failed to add OOM kill event for %q: %v", oomInstance.ContainerName, err)
			}
		}
	}()
	return nil
}

// can be called by the api which will take events returned on the channel
func (self *manager) WatchForEvents(request *events.Request) (*events.EventChannel, error) {
	return self.eventHandler.WatchEvents(request)
}

// can be called by the api which will return all events satisfying the request
func (self *manager) GetPastEvents(request *events.Request) ([]*info.Event, error) {
	return self.eventHandler.GetEvents(request)
}

// called by the api when a client is no longer listening to the channel
func (self *manager) CloseEventChannel(watch_id int) {
	self.eventHandler.StopWatch(watch_id)
}

// Parses the events StoragePolicy from the flags.
func parseEventsStoragePolicy() events.StoragePolicy {
	policy := events.DefaultStoragePolicy()

	// Parse max age.
	parts := strings.Split(*eventStorageAgeLimit, ",")
	for _, part := range parts {
		items := strings.Split(part, "=")
		if len(items) != 2 {
			glog.Warningf("Unknown event storage policy %q when parsing max age", part)
			continue
		}
		dur, err := time.ParseDuration(items[1])
		if err != nil {
			glog.Warningf("Unable to parse event max age duration %q: %v", items[1], err)
			continue
		}
		if items[0] == "default" {
			policy.DefaultMaxAge = dur
			continue
		}
		policy.PerTypeMaxAge[info.EventType(items[0])] = dur
	}

	// Parse max number.
	parts = strings.Split(*eventStorageEventLimit, ",")
	for _, part := range parts {
		items := strings.Split(part, "=")
		if len(items) != 2 {
			glog.Warningf("Unknown event storage policy %q when parsing max event limit", part)
			continue
		}
		val, err := strconv.Atoi(items[1])
		if err != nil {
			glog.Warningf("Unable to parse integer from %q: %v", items[1], err)
			continue
		}
		if items[0] == "default" {
			policy.DefaultMaxNumEvents = val
			continue
		}
		policy.PerTypeMaxNumEvents[info.EventType(items[0])] = val
	}

	return policy
}