Add restart monitor

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

restart/monitor/change.go

@@ -0,0 +1,75 @@
+/*
+   Copyright The containerd Authors.
+
+   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.
+*/
+
+package monitor
+
+import (
+	"context"
+	"syscall"
+
+	"github.com/containerd/containerd"
+	"github.com/containerd/containerd/cio"
+)
+
+type stopChange struct {
+	container containerd.Container
+}
+
+func (s *stopChange) apply(ctx context.Context, client *containerd.Client) error {
+	return killTask(ctx, s.container)
+}
+
+type startChange struct {
+	container containerd.Container
+	logPath   string
+}
+
+func (s *startChange) apply(ctx context.Context, client *containerd.Client) error {
+	log := cio.NullIO
+	if s.logPath != "" {
+		log = cio.LogFile(s.logPath)
+	}
+	killTask(ctx, s.container)
+	task, err := s.container.NewTask(ctx, log)
+	if err != nil {
+		return err
+	}
+	return task.Start(ctx)
+}
+
+func killTask(ctx context.Context, container containerd.Container) error {
+	task, err := container.Task(ctx, nil)
+	if err == nil {
+		wait, err := task.Wait(ctx)
+		if err != nil {
+			if _, derr := task.Delete(ctx); derr == nil {
+				return nil
+			}
+			return err
+		}
+		if err := task.Kill(ctx, syscall.SIGKILL, containerd.WithKillAll); err != nil {
+			if _, derr := task.Delete(ctx); derr == nil {
+				return nil
+			}
+			return err
+		}
+		<-wait
+		if _, err := task.Delete(ctx); err != nil {
+			return err
+		}
+	}
+	return nil
+}