Add ability to set CGroup Parent via API

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

libpod/container.go

@@ -83,7 +83,6 @@ type Container struct {
 // TODO Add readonly support
 // TODO add SHM size support
 // TODO add shared namespace support
-// TODO add cgroup parent support
 
 // containerRuntimeInfo contains the current state of the container
 // It is stored on disk in a tmpfs and recreated on reboot
@@ -1228,7 +1227,7 @@ func (c *Container) cleanupStorage() error {
 
 // CGroupPath returns a cgroups "path" for a given container.
 func (c *Container) CGroupPath() cgroups.Path {
-	return cgroups.StaticPath(filepath.Join(CgroupParent, fmt.Sprintf("libpod-conmon-%s", c.ID())))
+	return cgroups.StaticPath(filepath.Join(c.config.CgroupParent, fmt.Sprintf("libpod-conmon-%s", c.ID())))
 }
 
 // copyHostFileToRundir copies the provided file to the runtimedir

libpod/container_top.go

@@ -25,7 +25,7 @@ func (c *Container) GetContainerPids() ([]string, error) {
 // Gets the pids for a container without locking.  should only be called from a func where
 // locking has already been established.
 func (c *Container) getContainerPids() ([]string, error) {
-	taskFile := filepath.Join("/sys/fs/cgroup/pids", CgroupParent, fmt.Sprintf("libpod-conmon-%s", c.ID()), c.ID(), "tasks")
+	taskFile := filepath.Join("/sys/fs/cgroup/pids", c.config.CgroupParent, fmt.Sprintf("libpod-conmon-%s", c.ID()), c.ID(), "tasks")
 	logrus.Debug("reading pids from ", taskFile)
 	content, err := ioutil.ReadFile(taskFile)
 	if err != nil {

libpod/options.go

@@ -465,6 +465,23 @@ func WithNetNS(portMappings []ocicni.PortMapping) CtrCreateOption {
 	}
 }
 
+// WithCgroupParent sets the Cgroup Parent of the new container
+func WithCgroupParent(parent string) CtrCreateOption {
+	return func(ctr *Container) error {
+		if ctr.valid {
+			return ErrCtrFinalized
+		}
+
+		if parent == "" {
+			return errors.Wrapf(ErrInvalidArg, "cgroup parent cannot be empty")
+		}
+
+		ctr.config.CgroupParent = parent
+
+		return nil
+	}
+}
+
 // Pod Creation Options
 
 // WithPodName sets the name of the pod