Add per-pod CGroups

Pods can now create their own (cgroupfs) cgroups which containers
in them can (optionally) use.

This presently only works with CGroupFS, systemd cgroups are
still WIP

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

Closes: #784
Approved by: rhatdan

1 files changed, 68 insertions, 0 deletions

diff --git a/libpod/pod.go b/libpod/pod.go
index e082ef807..19347dde7 100644
--- a/libpod/pod.go
+++ b/libpod/pod.go
@@ -31,6 +31,11 @@ type PodConfig struct {
 	Labels map[string]string `json:"labels"`
 	// CgroupParent contains the pod's CGroup parent
 	CgroupParent string `json:"cgroupParent"`
+	// UsePodCgroup indicates whether the pod will create its own CGroup and
+	// join containers to it.
+	// If true, all containers joined to the pod will use the pod cgroup as
+	// their cgroup parent, and cannot set a different cgroup parent
+	UsePodCgroup bool
 }
 
 // podState represents a pod's state
@@ -64,6 +69,23 @@ func (p *Pod) CgroupParent() string {
 	return p.config.CgroupParent
 }
 
+// UsePodCgroup returns whether containers in the pod will default to this pod's
+// cgroup instead of the default libpod parent
+func (p *Pod) UsePodCgroup() bool {
+	return p.config.UsePodCgroup
+}
+
+// CgroupPath returns the path to the pod's CGroup
+func (p *Pod) CgroupPath() (string, error) {
+	p.lock.Lock()
+	p.lock.Unlock()
+	if err := p.updatePod(); err != nil {
+		return "", err
+	}
+
+	return p.state.CgroupPath, nil
+}
+
 // Creates a new, empty pod
 func newPod(lockDir string, runtime *Runtime) (*Pod, error) {
 	pod := new(Pod)
@@ -85,6 +107,52 @@ func newPod(lockDir string, runtime *Runtime) (*Pod, error) {
 	return pod, nil
 }
 
+// Update pod state from database
+func (p *Pod) updatePod() error {
+	if err := p.runtime.state.UpdatePod(p); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Save pod state to database
+func (p *Pod) save() error {
+	if err := p.runtime.state.SavePod(p); err != nil {
+		return errors.Wrapf(err, "error saving pod %s state")
+	}
+
+	return nil
+}
+
+// Refresh a pod's state after restart
+func (p *Pod) refresh() error {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+
+	if !p.valid {
+		return ErrPodRemoved
+	}
+
+	// We need to recreate the pod's cgroup
+	if p.config.UsePodCgroup {
+		switch p.runtime.config.CgroupManager {
+		case SystemdCgroupsManager:
+			// NOOP for now, until proper systemd cgroup management
+			// is implemented
+		case CgroupfsCgroupsManager:
+			p.state.CgroupPath = filepath.Join(p.config.CgroupParent, p.ID())
+
+			logrus.Debugf("setting pod cgroup to %s", p.state.CgroupPath)
+		default:
+			return errors.Wrapf(ErrInvalidArg, "unknown cgroups manager %s specified", p.runtime.config.CgroupManager)
+		}
+	}
+
+	// Save changes
+	return p.save()
+}
+
 // Start starts all containers within a pod
 // It combines the effects of Init() and Start() on a container
 // If a container has already been initialized it will be started,