kubelet/rkt: Add GarbageCollection to rkt runtime.

pkg/kubelet/rkt/gc.go

+/*
+Copyright 2015 Google Inc. All rights reserved.
+
+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 rkt
+
+import (
+	"os/exec"
+
+	"github.com/golang/glog"
+)
+
+const (
+	// TODO(yifan): Merge with ContainerGCPolicy, i.e., derive
+	// the grace period from MinAge in ContainerGCPolicy.
+	//
+	// Duration to wait before discarding inactive pods from garbage
+	defaultGracePeriod = "1m"
+	// Duration to wait before expiring prepared pods.
+	defaultExpirePrepared = "1m"
+)
+
+// GarbageCollect collects the pods/containers. TODO(yifan): Enforce the gc policy.
+func (r *Runtime) GarbageCollect() error {
+	if err := exec.Command("systemctl", "reset-failed").Run(); err != nil {
+		glog.Errorf("rkt: Failed to reset failed systemd services: %v", err)
+	}
+	if _, err := r.runCommand("gc", "--grace-period="+defaultGracePeriod, "--expire-prepared="+defaultExpirePrepared); err != nil {
+		glog.Errorf("rkt: Failed to gc: %v", err)
+		return err
+	}
+	return nil
+}
+
+// ImageManager manages and garbage collects the container images for rkt.
+type ImageManager struct {
+	runtime *Runtime
+}
+
+func NewImageManager(r *Runtime) *ImageManager {
+	return &ImageManager{runtime: r}
+}
+
+// GarbageCollect collects the images. It is not implemented by rkt yet.
+func (im *ImageManager) GarbageCollect() error {
+	return nil
+}