Move runtime interfaces to runtime package

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

runtime/monitor.go

@@ -0,0 +1,63 @@
+package runtime
+
+// TaskMonitor provides an interface for monitoring of containers within containerd
+type TaskMonitor interface {
+	// Monitor adds the provided container to the monitor
+	Monitor(Task) error
+	// Stop stops and removes the provided container from the monitor
+	Stop(Task) error
+	// Events emits events from the monitor
+	Events(chan<- *Event)
+}
+
+func NewMultiTaskMonitor(monitors ...TaskMonitor) TaskMonitor {
+	return &multiTaskMonitor{
+		monitors: monitors,
+	}
+}
+
+func NewNoopMonitor() TaskMonitor {
+	return &noopTaskMonitor{}
+}
+
+type noopTaskMonitor struct {
+}
+
+func (mm *noopTaskMonitor) Monitor(c Task) error {
+	return nil
+}
+
+func (mm *noopTaskMonitor) Stop(c Task) error {
+	return nil
+}
+
+func (mm *noopTaskMonitor) Events(events chan<- *Event) {
+}
+
+type multiTaskMonitor struct {
+	monitors []TaskMonitor
+}
+
+func (mm *multiTaskMonitor) Monitor(c Task) error {
+	for _, m := range mm.monitors {
+		if err := m.Monitor(c); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (mm *multiTaskMonitor) Stop(c Task) error {
+	for _, m := range mm.monitors {
+		if err := m.Stop(c); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (mm *multiTaskMonitor) Events(events chan<- *Event) {
+	for _, m := range mm.monitors {
+		m.Events(events)
+	}
+}