Move supervisor to it's own package

It allows to keep main namespace cleaner

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

supervisor/worker.go

@@ -0,0 +1,86 @@
+package supervisor
+
+import (
+	"sync"
+	"time"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/docker/containerd/runtime"
+)
+
+type Worker interface {
+	Start()
+}
+
+type StartTask struct {
+	Container     runtime.Container
+	Checkpoint    string
+	IO            *runtime.IO
+	Stdin         string
+	Stdout        string
+	Stderr        string
+	Err           chan error
+	StartResponse chan StartResponse
+}
+
+func NewWorker(s *Supervisor, wg *sync.WaitGroup) Worker {
+	return &worker{
+		s:  s,
+		wg: wg,
+	}
+}
+
+type worker struct {
+	wg *sync.WaitGroup
+	s  *Supervisor
+}
+
+func (w *worker) Start() {
+	defer w.wg.Done()
+	for t := range w.s.tasks {
+		started := time.Now()
+		l, err := w.s.copyIO(t.Stdin, t.Stdout, t.Stderr, t.IO)
+		if err != nil {
+			evt := NewEvent(DeleteEventType)
+			evt.ID = t.Container.ID()
+			w.s.SendEvent(evt)
+			t.Err <- err
+			continue
+		}
+		w.s.containers[t.Container.ID()].copier = l
+		if t.Checkpoint != "" {
+			if err := t.Container.Restore(t.Checkpoint); err != nil {
+				evt := NewEvent(DeleteEventType)
+				evt.ID = t.Container.ID()
+				w.s.SendEvent(evt)
+				t.Err <- err
+				continue
+			}
+		} else {
+			if err := t.Container.Start(); err != nil {
+				evt := NewEvent(DeleteEventType)
+				evt.ID = t.Container.ID()
+				w.s.SendEvent(evt)
+				t.Err <- err
+				continue
+			}
+		}
+		pid, err := t.Container.Pid()
+		if err != nil {
+			logrus.WithField("error", err).Error("containerd: get container main pid")
+		}
+		if w.s.notifier != nil {
+			n, err := t.Container.OOM()
+			if err != nil {
+				logrus.WithField("error", err).Error("containerd: notify OOM events")
+			} else {
+				w.s.notifier.Add(n, t.Container.ID())
+			}
+		}
+		ContainerStartTimer.UpdateSince(started)
+		t.Err <- nil
+		t.StartResponse <- StartResponse{
+			Pid: pid,
+		}
+	}
+}