Store cgroup manager on a per-container basis

libpod/container.go

@@ -888,9 +888,22 @@ func (c *Container) NamespacePath(linuxNS LinuxNS) (string, error) { //nolint:in
 	return fmt.Sprintf("/proc/%d/ns/%s", c.state.PID, linuxNS.String()), nil
 }
 
+// CgroupManager returns the cgroup manager used by the given container.
+func (c *Container) CgroupManager() string {
+	cgroupManager := c.config.CgroupManager
+	if cgroupManager == "" {
+		cgroupManager = c.runtime.config.Engine.CgroupManager
+	}
+	return cgroupManager
+}
+
 // CGroupPath returns a cgroups "path" for a given container.
 func (c *Container) CGroupPath() (string, error) {
+	cgroupManager := c.CgroupManager()
+
 	switch {
+	case c.config.NoCgroups || c.config.CgroupsMode == "disabled":
+		return "", errors.Wrapf(define.ErrNoCgroups, "this container is not creating cgroups")
 	case c.config.CgroupsMode == cgroupSplit:
 		if c.config.CgroupParent != "" {
 			return "", errors.Errorf("cannot specify cgroup-parent with cgroup-mode %q", cgroupSplit)
@@ -906,9 +919,9 @@ func (c *Container) CGroupPath() (string, error) {
 			return "", errors.Errorf("invalid cgroup for conmon %q", cg)
 		}
 		return strings.TrimSuffix(cg, "/supervisor") + "/container", nil
-	case c.runtime.config.Engine.CgroupManager == config.CgroupfsCgroupsManager:
+	case cgroupManager == config.CgroupfsCgroupsManager:
 		return filepath.Join(c.config.CgroupParent, fmt.Sprintf("libpod-%s", c.ID())), nil
-	case c.runtime.config.Engine.CgroupManager == config.SystemdCgroupsManager:
+	case cgroupManager == config.SystemdCgroupsManager:
 		if rootless.IsRootless() {
 			uid := rootless.GetRootlessUID()
 			parts := strings.SplitN(c.config.CgroupParent, "/", 2)
@@ -922,7 +935,7 @@ func (c *Container) CGroupPath() (string, error) {
 		}
 		return filepath.Join(c.config.CgroupParent, createUnitName("libpod", c.ID())), nil
 	default:
-		return "", errors.Wrapf(define.ErrInvalidArg, "unsupported CGroup manager %s in use", c.runtime.config.Engine.CgroupManager)
+		return "", errors.Wrapf(define.ErrInvalidArg, "unsupported CGroup manager %s in use", cgroupManager)
 	}
 }
 

libpod/container_config.go

@@ -275,13 +275,16 @@ type ContainerMiscConfig struct {
 	StopTimeout uint `json:"stopTimeout,omitempty"`
 	// Time container was created
 	CreatedTime time.Time `json:"createdTime"`
+	// CgroupManager is the cgroup manager used to create this container.
+	// If empty, the runtime default will be used.
+	CgroupManager string `json:"cgroupManager,omitempty"`
 	// NoCgroups indicates that the container will not create CGroups. It is
 	// incompatible with CgroupParent.  Deprecated in favor of CgroupsMode.
 	NoCgroups bool `json:"noCgroups,omitempty"`
 	// CgroupsMode indicates how the container will create cgroups
 	// (disabled, no-conmon, enabled).  It supersedes NoCgroups.
 	CgroupsMode string `json:"cgroupsMode,omitempty"`
-	// Cgroup parent of the container
+	// Cgroup parent of the container.
 	CgroupParent string `json:"cgroupParent"`
 	// LogPath log location
 	LogPath string `json:"logPath"`

libpod/container_inspect.go

@@ -729,7 +729,7 @@ func (c *Container) generateInspectContainerHostConfig(ctrSpec *spec.Spec, named
 	// CGroup parent
 	// Need to check if it's the default, and not print if so.
 	defaultCgroupParent := ""
-	switch c.runtime.config.Engine.CgroupManager {
+	switch c.CgroupManager() {
 	case config.CgroupfsCgroupsManager:
 		defaultCgroupParent = CgroupfsDefaultCgroupParent
 	case config.SystemdCgroupsManager:
@@ -738,6 +738,7 @@ func (c *Container) generateInspectContainerHostConfig(ctrSpec *spec.Spec, named
 	if c.config.CgroupParent != defaultCgroupParent {
 		hostConfig.CgroupParent = c.config.CgroupParent
 	}
+	hostConfig.CgroupManager = c.CgroupManager()
 
 	// PID namespace mode
 	pidMode := ""

libpod/container_internal_linux.go

@@ -1965,6 +1965,7 @@ func (c *Container) getOCICgroupPath() (string, error) {
 	if err != nil {
 		return "", err
 	}
+	cgroupManager := c.CgroupManager()
 	switch {
 	case (rootless.IsRootless() && !unified) || c.config.NoCgroups:
 		return "", nil
@@ -1977,22 +1978,22 @@ func (c *Container) getOCICgroupPath() (string, error) {
 			return "", err
 		}
 		return filepath.Join(selfCgroup, "container"), nil
-	case c.runtime.config.Engine.CgroupManager == config.SystemdCgroupsManager:
+	case cgroupManager == config.SystemdCgroupsManager:
 		// When the OCI runtime is set to use Systemd as a cgroup manager, it
 		// expects cgroups to be passed as follows:
 		// slice:prefix:name
 		systemdCgroups := fmt.Sprintf("%s:libpod:%s", path.Base(c.config.CgroupParent), c.ID())
 		logrus.Debugf("Setting CGroups for container %s to %s", c.ID(), systemdCgroups)
 		return systemdCgroups, nil
-	case c.runtime.config.Engine.CgroupManager == config.CgroupfsCgroupsManager:
+	case cgroupManager == config.CgroupfsCgroupsManager:
 		cgroupPath, err := c.CGroupPath()
 		if err != nil {
 			return "", err
 		}
 		logrus.Debugf("Setting CGroup path for container %s to %s", c.ID(), cgroupPath)
 		return cgroupPath, nil
 	default:
-		return "", errors.Wrapf(define.ErrInvalidArg, "invalid cgroup manager %s requested", c.runtime.config.Engine.CgroupManager)
+		return "", errors.Wrapf(define.ErrInvalidArg, "invalid cgroup manager %s requested", cgroupManager)
 	}
 }
 

libpod/define/container_inspect.go

@@ -236,6 +236,9 @@ type InspectContainerHostConfig struct {
 	// include a Mounts field in inspect.
 	// Format: <src>:<destination>[:<comma-separated options>]
 	Binds []string `json:"Binds"`
+	// CgroupManager is the cgroup manager used by the container.
+	// At present, allowed values are either "cgroupfs" or "systemd".
+	CgroupManager string `json:"CgroupManager,omitempty"`
 	// CgroupMode is the configuration of the container's cgroup namespace.
 	// Populated as follows:
 	// private - a cgroup namespace has been created

libpod/oci_conmon_linux.go

@@ -57,7 +57,6 @@ type ConmonOCIRuntime struct {
 	path              string
 	conmonPath        string
 	conmonEnv         []string
-	cgroupManager     string
 	tmpDir            string
 	exitsDir          string
 	socketsDir        string
@@ -102,7 +101,6 @@ func newConmonOCIRuntime(name string, paths []string, conmonPath string, runtime
 	runtime.runtimeFlags = runtimeFlags
 
 	runtime.conmonEnv = runtimeCfg.Engine.ConmonEnvVars
-	runtime.cgroupManager = runtimeCfg.Engine.CgroupManager
 	runtime.tmpDir = runtimeCfg.Engine.TmpDir
 	runtime.logSizeMax = runtimeCfg.Containers.LogSizeMax
 	runtime.noPivot = runtimeCfg.Engine.NoPivotRoot
@@ -149,10 +147,6 @@ func newConmonOCIRuntime(name string, paths []string, conmonPath string, runtime
 	runtime.exitsDir = filepath.Join(runtime.tmpDir, "exits")
 	runtime.socketsDir = filepath.Join(runtime.tmpDir, "socket")
 
-	if runtime.cgroupManager != config.CgroupfsCgroupsManager && runtime.cgroupManager != config.SystemdCgroupsManager {
-		return nil, errors.Wrapf(define.ErrInvalidArg, "invalid cgroup manager specified: %s", runtime.cgroupManager)
-	}
-
 	// Create the exit files and attach sockets directories
 	if err := os.MkdirAll(runtime.exitsDir, 0750); err != nil {
 		// The directory is allowed to exist
@@ -1325,7 +1319,7 @@ func (r *ConmonOCIRuntime) sharedConmonArgs(ctr *Container, cuuid, bundlePath, p
 		args = append(args, rFlags...)
 	}
 
-	if r.cgroupManager == config.SystemdCgroupsManager && !ctr.config.NoCgroups && ctr.config.CgroupsMode != cgroupSplit {
+	if ctr.CgroupManager() == config.SystemdCgroupsManager && !ctr.config.NoCgroups && ctr.config.CgroupsMode != cgroupSplit {
 		args = append(args, "-s")
 	}
 
@@ -1442,8 +1436,10 @@ func (r *ConmonOCIRuntime) moveConmonToCgroupAndSignal(ctr *Container, cmd *exec
 	}
 
 	if mustCreateCgroup {
+		// TODO: This should be a switch - we are not guaranteed that
+		// there are only 2 valid cgroup managers
 		cgroupParent := ctr.CgroupParent()
-		if r.cgroupManager == config.SystemdCgroupsManager {
+		if ctr.CgroupManager() == config.SystemdCgroupsManager {
 			unitName := createUnitName("libpod-conmon", ctr.ID())
 
 			realCgroupParent := cgroupParent

libpod/runtime_ctr.go

@@ -208,6 +208,7 @@ func (r *Runtime) setupContainer(ctx context.Context, ctr *Container) (_ *Contai
 	// Check CGroup parent sanity, and set it if it was not set.
 	// Only if we're actually configuring CGroups.
 	if !ctr.config.NoCgroups {
+		ctr.config.CgroupManager = r.config.Engine.CgroupManager
 		switch r.config.Engine.CgroupManager {
 		case config.CgroupfsCgroupsManager:
 			if ctr.config.CgroupParent == "" {