Add event logging to libpod, even display to podman

In lipod, we now log major events that occurr.  These events
can be displayed using the `podman events` command. Each
event contains:

* Type (container, image, volume, pod...)
* Status (create, rm, stop, kill, ....)
* Timestamp in RFC3339Nano format
* Name (if applicable)
* Image (if applicable)

The format of the event and the varlink endpoint are to not
be considered stable until cockpit has done its enablement.

Signed-off-by: baude <bbaude@redhat.com>

libpod/events/events.go

@@ -0,0 +1,264 @@
+package events
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+// Event describes the attributes of a libpod event
+type Event struct {
+	// ContainerExitCode is for storing the exit code of a container which can
+	// be used for "internal" event notification
+	ContainerExitCode int
+	// ID can be for the container, image, volume, etc
+	ID string
+	// Image used where applicable
+	Image string
+	// Name where applicable
+	Name string
+	// Status describes the event that occurred
+	Status Status
+	// Time the event occurred
+	Time time.Time
+	// Type of event that occurred
+	Type Type
+}
+
+// Type of event that occurred (container, volume, image, pod, etc)
+type Type string
+
+// Status describes the actual event action (stop, start, create, kill)
+type Status string
+
+const (
+	// If you add or subtract any values to the following lists, make sure you also update
+	// the switch statements below and the enums for EventType or EventStatus in the
+	// varlink description file.
+
+	// Container - event is related to containers
+	Container Type = "container"
+	// Image - event is related to images
+	Image Type = "image"
+	// Pod - event is related to pods
+	Pod Type = "pod"
+	// Volume - event is related to volumes
+	Volume Type = "volume"
+
+	// Attach ...
+	Attach Status = "attach"
+	// Checkpoint ...
+	Checkpoint Status = "checkpoint"
+	// Cleanup ...
+	Cleanup Status = "cleanup"
+	// Commit ...
+	Commit Status = "commit"
+	// Create ...
+	Create Status = "create"
+	// Exec ...
+	Exec Status = "exec"
+	// Export ...
+	Export Status = "export"
+	// History ...
+	History Status = "history"
+	// Import ...
+	Import Status = "import"
+	// Init ...
+	Init Status = "init"
+	// Kill ...
+	Kill Status = "kill"
+	// LoadFromArchive ...
+	LoadFromArchive Status = "status"
+	// Mount ...
+	Mount Status = "mount"
+	// Pause ...
+	Pause Status = "pause"
+	// Prune ...
+	Prune Status = "prune"
+	// Pull ...
+	Pull Status = "pull"
+	// Push ...
+	Push Status = "push"
+	// Remove ...
+	Remove Status = "remove"
+	// Restore ...
+	Restore Status = "restore"
+	// Save ...
+	Save Status = "save"
+	// Start ...
+	Start Status = "start"
+	// Stop ...
+	Stop Status = "stop"
+	// Sync ...
+	Sync Status = "sync"
+	// Tag ...
+	Tag Status = "tag"
+	// Unmount ...
+	Unmount Status = "unmount"
+	// Unpause ...
+	Unpause Status = "unpause"
+	// Untag ...
+	Untag Status = "untag"
+	// Wait ...
+	Wait Status = "wait"
+)
+
+// EventFilter for filtering events
+type EventFilter func(*Event) bool
+
+// NewEvent creates a event struct and populates with
+// the given status and time.
+func NewEvent(status Status) Event {
+	return Event{
+		Status: status,
+		Time:   time.Now(),
+	}
+}
+
+// Write will record the event to the given path
+func (e *Event) Write(path string) error {
+	f, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0700)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	eventJSONString, err := e.ToJSONString()
+	if err != nil {
+		return err
+	}
+	if _, err := f.WriteString(fmt.Sprintf("%s\n", eventJSONString)); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Recycle checks if the event log has reach a limit and if so
+// renames the current log and starts a new one.  The remove bool
+// indicates the old log file should be deleted.
+func (e *Event) Recycle(path string, remove bool) error {
+	return errors.New("not implemented")
+}
+
+// ToJSONString returns the event as a json'ified string
+func (e *Event) ToJSONString() (string, error) {
+	b, err := json.Marshal(e)
+	return string(b), err
+}
+
+// ToHumanReadable returns human readable event as a formatted string
+func (e *Event) ToHumanReadable() string {
+	var humanFormat string
+	switch e.Type {
+	case Container, Pod:
+		humanFormat = fmt.Sprintf("%s %s %s %s (image=%s, name=%s)", e.Time, e.Type, e.Status, e.ID, e.Image, e.Name)
+	case Image:
+		humanFormat = fmt.Sprintf("%s %s %s %s %s", e.Time, e.Type, e.Status, e.ID, e.Name)
+	case Volume:
+		humanFormat = fmt.Sprintf("%s %s %s %s", e.Time, e.Type, e.Status, e.Name)
+	}
+	return humanFormat
+}
+
+// NewEventFromString takes stringified json and converts
+// it to an event
+func NewEventFromString(event string) (*Event, error) {
+	e := Event{}
+	if err := json.Unmarshal([]byte(event), &e); err != nil {
+		return nil, err
+	}
+	return &e, nil
+
+}
+
+// ToString converts a Type to a string
+func (t Type) String() string {
+	return string(t)
+}
+
+// ToString converts a status to a string
+func (s Status) String() string {
+	return string(s)
+}
+
+// StringToType converts string to an EventType
+func StringToType(name string) (Type, error) {
+	switch name {
+	case Container.String():
+		return Container, nil
+	case Image.String():
+		return Image, nil
+	case Pod.String():
+		return Pod, nil
+	case Volume.String():
+		return Volume, nil
+	}
+	return "", errors.Errorf("unknown event type %s", name)
+}
+
+// StringToStatus converts a string to an Event Status
+// TODO if we add more events, we might consider a go-generator to
+// create the switch statement
+func StringToStatus(name string) (Status, error) {
+	switch name {
+	case Attach.String():
+		return Attach, nil
+	case Checkpoint.String():
+		return Checkpoint, nil
+	case Restore.String():
+		return Restore, nil
+	case Cleanup.String():
+		return Cleanup, nil
+	case Commit.String():
+		return Commit, nil
+	case Create.String():
+		return Create, nil
+	case Exec.String():
+		return Exec, nil
+	case Export.String():
+		return Export, nil
+	case History.String():
+		return History, nil
+	case Import.String():
+		return Import, nil
+	case Init.String():
+		return Init, nil
+	case Kill.String():
+		return Kill, nil
+	case LoadFromArchive.String():
+		return LoadFromArchive, nil
+	case Mount.String():
+		return Mount, nil
+	case Pause.String():
+		return Pause, nil
+	case Prune.String():
+		return Prune, nil
+	case Pull.String():
+		return Pull, nil
+	case Push.String():
+		return Push, nil
+	case Remove.String():
+		return Remove, nil
+	case Save.String():
+		return Save, nil
+	case Start.String():
+		return Start, nil
+	case Stop.String():
+		return Stop, nil
+	case Sync.String():
+		return Sync, nil
+	case Tag.String():
+		return Tag, nil
+	case Unmount.String():
+		return Unmount, nil
+	case Unpause.String():
+		return Unpause, nil
+	case Untag.String():
+		return Untag, nil
+	case Wait.String():
+		return Wait, nil
+	}
+	return "", errors.Errorf("unknown event status %s", name)
+}