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.go

@@ -0,0 +1,81 @@
+package libpod
+
+import (
+	"github.com/containers/libpod/libpod/events"
+	"github.com/hpcloud/tail"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+)
+
+// newContainerEvent creates a new event based on a container
+func (c *Container) newContainerEvent(status events.Status) {
+	e := events.NewEvent(status)
+	e.ID = c.ID()
+	e.Name = c.Name()
+	e.Image = c.config.RootfsImageName
+	e.Type = events.Container
+	if err := e.Write(c.runtime.config.EventsLogFilePath); err != nil {
+		logrus.Errorf("unable to write event to %s", c.runtime.config.EventsLogFilePath)
+	}
+}
+
+// newPodEvent creates a new event for a libpod pod
+func (p *Pod) newPodEvent(status events.Status) {
+	e := events.NewEvent(status)
+	e.ID = p.ID()
+	e.Name = p.Name()
+	e.Type = events.Pod
+	if err := e.Write(p.runtime.config.EventsLogFilePath); err != nil {
+		logrus.Errorf("unable to write event to %s", p.runtime.config.EventsLogFilePath)
+	}
+}
+
+// newVolumeEvent creates a new event for a libpod volume
+func (v *Volume) newVolumeEvent(status events.Status) {
+	e := events.NewEvent(status)
+	e.Name = v.Name()
+	e.Type = events.Volume
+	if err := e.Write(v.runtime.config.EventsLogFilePath); err != nil {
+		logrus.Errorf("unable to write event to %s", v.runtime.config.EventsLogFilePath)
+	}
+}
+
+// Events is a wrapper function for everyone to begin tailing the events log
+// with options
+func (r *Runtime) Events(fromStart, stream bool, options []events.EventFilter, eventChannel chan *events.Event) error {
+	t, err := r.getTail(fromStart, stream)
+	if err != nil {
+		return err
+	}
+	for line := range t.Lines {
+		event, err := events.NewEventFromString(line.Text)
+		if err != nil {
+			return err
+		}
+		switch event.Type {
+		case events.Image, events.Volume, events.Pod, events.Container:
+		//	no-op
+		default:
+			return errors.Errorf("event type %s is not valid in %s", event.Type.String(), r.GetConfig().EventsLogFilePath)
+		}
+		include := true
+		for _, filter := range options {
+			include = include && filter(event)
+		}
+		if include {
+			eventChannel <- event
+		}
+	}
+	close(eventChannel)
+	return nil
+}
+
+func (r *Runtime) getTail(fromStart, stream bool) (*tail.Tail, error) {
+	reopen := true
+	seek := tail.SeekInfo{Offset: 0, Whence: 2}
+	if fromStart || !stream {
+		seek.Whence = 0
+		reopen = false
+	}
+	return tail.TailFile(r.config.EventsLogFilePath, tail.Config{ReOpen: reopen, Follow: stream, Location: &seek})
+}