[release-4.17] OCPBUGS-43820: UPSTREAM: <carry>: kubelet/cm: fix bug where kubelet restarts from missing cpuset cgroup

pkg/kubelet/cm/cgroup_manager_linux.go

@@ -384,6 +384,9 @@ func (m *cgroupManagerImpl) toResources(resourceConfig *ResourceConfig) *libcont
 	if resourceConfig.PidsLimit != nil {
 		resources.PidsLimit = *resourceConfig.PidsLimit
 	}
+	if !resourceConfig.CPUSet.IsEmpty() {
+		resources.CpusetCpus = resourceConfig.CPUSet.String()
+	}
 
 	m.maybeSetHugetlb(resourceConfig, resources)
 

pkg/kubelet/cm/cpumanager/cpu_manager.go

@@ -94,6 +94,10 @@ type Manager interface {
 	// GetCPUAffinity returns cpuset which includes cpus from shared pools
 	// as well as exclusively allocated cpus
 	GetCPUAffinity(podUID, containerName string) cpuset.CPUSet
+
+	// GetAllCPUs returns all the CPUs known by cpumanager, as reported by the
+	// hardware discovery. Maps to the CPU capacity.
+	GetAllCPUs() cpuset.CPUSet
 }
 
 type manager struct {
@@ -137,7 +141,11 @@ type manager struct {
 	// stateFileDirectory holds the directory where the state file for checkpoints is held.
 	stateFileDirectory string
 
-	// allocatableCPUs is the set of online CPUs as reported by the system
+	// allCPUs is the set of online CPUs as reported by the system
+	allCPUs cpuset.CPUSet
+
+	// allocatableCPUs is the set of online CPUs as reported by the system,
+	// and available for allocation, minus the reserved set
 	allocatableCPUs cpuset.CPUSet
 
 	// pendingAdmissionPod contain the pod during the admission phase
@@ -157,6 +165,11 @@ func NewManager(cpuPolicyName string, cpuPolicyOptions map[string]string, reconc
 	var policy Policy
 	var err error
 
+	topo, err = topology.Discover(machineInfo)
+	if err != nil {
+		return nil, err
+	}
+
 	switch policyName(cpuPolicyName) {
 
 	case PolicyNone:
@@ -166,10 +179,6 @@ func NewManager(cpuPolicyName string, cpuPolicyOptions map[string]string, reconc
 		}
 
 	case PolicyStatic:
-		topo, err = topology.Discover(machineInfo)
-		if err != nil {
-			return nil, err
-		}
 		klog.InfoS("Detected CPU topology", "topology", topo)
 
 		reservedCPUs, ok := nodeAllocatableReservation[v1.ResourceCPU]
@@ -206,6 +215,7 @@ func NewManager(cpuPolicyName string, cpuPolicyOptions map[string]string, reconc
 		topology:                   topo,
 		nodeAllocatableReservation: nodeAllocatableReservation,
 		stateFileDirectory:         stateFileDirectory,
+		allCPUs:                    topo.CPUDetails.CPUs(),
 	}
 	manager.sourcesReady = &sourcesReadyStub{}
 	return manager, nil
@@ -340,6 +350,10 @@ func (m *manager) GetAllocatableCPUs() cpuset.CPUSet {
 	return m.allocatableCPUs.Clone()
 }
 
+func (m *manager) GetAllCPUs() cpuset.CPUSet {
+	return m.allCPUs.Clone()
+}
+
 type reconciledContainer struct {
 	podName       string
 	containerName string

pkg/kubelet/cm/cpumanager/cpu_manager_test.go

@@ -693,15 +693,8 @@ func TestCPUManagerGenerate(t *testing.T) {
 				if rawMgr.policy.Name() != testCase.expectedPolicy {
 					t.Errorf("Unexpected policy name. Have: %q wants %q", rawMgr.policy.Name(), testCase.expectedPolicy)
 				}
-				if rawMgr.policy.Name() == string(PolicyNone) {
-					if rawMgr.topology != nil {
-						t.Errorf("Expected topology to be nil for 'none' policy. Have: %q", rawMgr.topology)
-					}
-				}
-				if rawMgr.policy.Name() != string(PolicyNone) {
-					if rawMgr.topology == nil {
-						t.Errorf("Expected topology to be non-nil for policy '%v'. Have: %q", rawMgr.policy.Name(), rawMgr.topology)
-					}
+				if rawMgr.topology == nil {
+					t.Errorf("Expected topology to be non-nil for policy '%v'. Have: %q", rawMgr.policy.Name(), rawMgr.topology)
 				}
 			}
 		})

pkg/kubelet/cm/cpumanager/fake_cpu_manager.go

@@ -85,6 +85,11 @@ func (m *fakeManager) GetCPUAffinity(podUID, containerName string) cpuset.CPUSet
 	return cpuset.CPUSet{}
 }
 
+func (m *fakeManager) GetAllCPUs() cpuset.CPUSet {
+	klog.InfoS("GetAllCPUs")
+	return cpuset.CPUSet{}
+}
+
 // NewFakeManager creates empty/fake cpu manager
 func NewFakeManager() Manager {
 	return &fakeManager{

pkg/kubelet/cm/node_container_manager_linux.go

@@ -52,7 +52,7 @@ func (cm *containerManagerImpl) createNodeAllocatableCgroups() error {
 	cgroupConfig := &CgroupConfig{
 		Name: cm.cgroupRoot,
 		// The default limits for cpu shares can be very low which can lead to CPU starvation for pods.
-		ResourceParameters: getCgroupConfig(nodeAllocatable),
+		ResourceParameters: cm.getCgroupConfig(nodeAllocatable),
 	}
 	if cm.cgroupManager.Exists(cgroupConfig.Name) {
 		return nil
@@ -80,7 +80,7 @@ func (cm *containerManagerImpl) enforceNodeAllocatableCgroups() error {
 
 	cgroupConfig := &CgroupConfig{
 		Name:               cm.cgroupRoot,
-		ResourceParameters: getCgroupConfig(nodeAllocatable),
+		ResourceParameters: cm.getCgroupConfig(nodeAllocatable),
 	}
 
 	// Using ObjectReference for events as the node maybe not cached; refer to #42701 for detail.
@@ -114,7 +114,7 @@ func (cm *containerManagerImpl) enforceNodeAllocatableCgroups() error {
 	// Now apply kube reserved and system reserved limits if required.
 	if nc.EnforceNodeAllocatable.Has(kubetypes.SystemReservedEnforcementKey) {
 		klog.V(2).InfoS("Enforcing system reserved on cgroup", "cgroupName", nc.SystemReservedCgroupName, "limits", nc.SystemReserved)
-		if err := enforceExistingCgroup(cm.cgroupManager, cm.cgroupManager.CgroupName(nc.SystemReservedCgroupName), nc.SystemReserved); err != nil {
+		if err := cm.enforceExistingCgroup(nc.SystemReservedCgroupName, nc.SystemReserved); err != nil {
 			message := fmt.Sprintf("Failed to enforce System Reserved Cgroup Limits on %q: %v", nc.SystemReservedCgroupName, err)
 			cm.recorder.Event(nodeRef, v1.EventTypeWarning, events.FailedNodeAllocatableEnforcement, message)
 			return fmt.Errorf(message)
@@ -123,7 +123,7 @@ func (cm *containerManagerImpl) enforceNodeAllocatableCgroups() error {
 	}
 	if nc.EnforceNodeAllocatable.Has(kubetypes.KubeReservedEnforcementKey) {
 		klog.V(2).InfoS("Enforcing kube reserved on cgroup", "cgroupName", nc.KubeReservedCgroupName, "limits", nc.KubeReserved)
-		if err := enforceExistingCgroup(cm.cgroupManager, cm.cgroupManager.CgroupName(nc.KubeReservedCgroupName), nc.KubeReserved); err != nil {
+		if err := cm.enforceExistingCgroup(nc.KubeReservedCgroupName, nc.KubeReserved); err != nil {
 			message := fmt.Sprintf("Failed to enforce Kube Reserved Cgroup Limits on %q: %v", nc.KubeReservedCgroupName, err)
 			cm.recorder.Event(nodeRef, v1.EventTypeWarning, events.FailedNodeAllocatableEnforcement, message)
 			return fmt.Errorf(message)
@@ -134,8 +134,9 @@ func (cm *containerManagerImpl) enforceNodeAllocatableCgroups() error {
 }
 
 // enforceExistingCgroup updates the limits `rl` on existing cgroup `cName` using `cgroupManager` interface.
-func enforceExistingCgroup(cgroupManager CgroupManager, cName CgroupName, rl v1.ResourceList) error {
-	rp := getCgroupConfig(rl)
+func (cm *containerManagerImpl) enforceExistingCgroup(cNameStr string, rl v1.ResourceList) error {
+	cName := cm.cgroupManager.CgroupName(cNameStr)
+	rp := cm.getCgroupConfig(rl)
 	if rp == nil {
 		return fmt.Errorf("%q cgroup is not configured properly", cName)
 	}
@@ -156,17 +157,17 @@ func enforceExistingCgroup(cgroupManager CgroupManager, cName CgroupName, rl v1.
 		ResourceParameters: rp,
 	}
 	klog.V(4).InfoS("Enforcing limits on cgroup", "cgroupName", cName, "cpuShares", cgroupConfig.ResourceParameters.CPUShares, "memory", cgroupConfig.ResourceParameters.Memory, "pidsLimit", cgroupConfig.ResourceParameters.PidsLimit)
-	if err := cgroupManager.Validate(cgroupConfig.Name); err != nil {
+	if err := cm.cgroupManager.Validate(cgroupConfig.Name); err != nil {
 		return err
 	}
-	if err := cgroupManager.Update(cgroupConfig); err != nil {
+	if err := cm.cgroupManager.Update(cgroupConfig); err != nil {
 		return err
 	}
 	return nil
 }
 
 // getCgroupConfig returns a ResourceConfig object that can be used to create or update cgroups via CgroupManager interface.
-func getCgroupConfig(rl v1.ResourceList) *ResourceConfig {
+func (cm *containerManagerImpl) getCgroupConfig(rl v1.ResourceList) *ResourceConfig {
 	// TODO(vishh): Set CPU Quota if necessary.
 	if rl == nil {
 		return nil
@@ -188,6 +189,18 @@ func getCgroupConfig(rl v1.ResourceList) *ResourceConfig {
 	}
 	rc.HugePageLimit = HugePageLimits(rl)
 
+	// In the case of a None policy, cgroupv2 and systemd cgroup manager, we must make sure systemd is aware of the cpuset cgroup.
+	// By default, systemd will not create it, as we've not chosen to delegate it, and we haven't included it in the Apply() request.
+	// However, this causes a bug where kubelet restarts unnecessarily (cpuset cgroup is created in the cgroupfs, but systemd
+	// doesn't know about it and deletes it, and then kubelet doesn't continue because the cgroup isn't configured as expected).
+	// An alternative is to delegate the `cpuset` cgroup to the kubelet, but that would require some plumbing in libcontainer,
+	// and this is sufficient.
+	// Only do so on None policy, as Static policy will do its own updating of the cpuset.
+	// Please see the comment on policy none's GetAllocatableCPUs
+	if cm.cpuManager.GetAllocatableCPUs().IsEmpty() {
+		rc.CPUSet = cm.cpuManager.GetAllCPUs()
+	}
+
 	return &rc
 }
 

pkg/kubelet/cm/types.go

@@ -19,12 +19,15 @@ package cm
 import (
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/utils/cpuset"
 )
 
 // ResourceConfig holds information about all the supported cgroup resource parameters.
 type ResourceConfig struct {
 	// Memory limit (in bytes).
 	Memory *int64
+	// CPU set (number of cpus the cgroup has access to).
+	CPUSet cpuset.CPUSet
 	// CPU shares (relative weight vs. other containers).
 	CPUShares *uint64
 	// CPU hardcap limit (in usecs). Allowed cpu time in a given period.

test/e2e_node/node_container_manager_test.go

@@ -72,6 +72,63 @@ var _ = SIGDescribe("Node Container Manager", framework.WithSerial(), func() {
 			framework.ExpectNoError(runTest(ctx, f))
 		})
 	})
+	f.Describe("Validate CGroup management", func() {
+		// Regression test for https://issues.k8s.io/125923
+		// In this issue there's a race involved with systemd which seems to manifest most likely, or perhaps only
+		// (data gathered so far seems inconclusive) on the very first boot of the machine, so restarting the kubelet
+		// seems not sufficient. OTOH, the exact reproducer seems to require a dedicate lane with only this test, or
+		// to reboot the machine before to run this test. Both are practically unrealistic in CI.
+		// The closest approximation is this test in this current form, using a kubelet restart. This at least
+		// acts as non regression testing, so it still brings value.
+		ginkgo.It("should correctly start with cpumanager none policy in use with systemd", func(ctx context.Context) {
+			if !IsCgroup2UnifiedMode() {
+				ginkgo.Skip("this test requires cgroups v2")
+			}
+
+			var err error
+			var oldCfg *kubeletconfig.KubeletConfiguration
+			// Get current kubelet configuration
+			oldCfg, err = getCurrentKubeletConfig(ctx)
+			framework.ExpectNoError(err)
+
+			ginkgo.DeferCleanup(func(ctx context.Context) {
+				if oldCfg != nil {
+					// Update the Kubelet configuration.
+					framework.ExpectNoError(e2enodekubelet.WriteKubeletConfigFile(oldCfg))
+
+					ginkgo.By("Restarting the kubelet")
+					restartKubelet(true)
+
+					// wait until the kubelet health check will succeed
+					gomega.Eventually(ctx, func(ctx context.Context) bool {
+						return kubeletHealthCheck(kubeletHealthCheckURL)
+					}).WithTimeout(2 * time.Minute).WithPolling(5 * time.Second).Should(gomega.BeTrueBecause("expected kubelet to be in healthy state"))
+					ginkgo.By("Started the kubelet")
+				}
+			})
+
+			newCfg := oldCfg.DeepCopy()
+			// Change existing kubelet configuration
+			newCfg.CPUManagerPolicy = "none"
+			newCfg.CgroupDriver = "systemd"
+
+			// Update the Kubelet configuration.
+			framework.ExpectNoError(e2enodekubelet.WriteKubeletConfigFile(newCfg))
+
+			ginkgo.By("Restarting the kubelet")
+			restartKubelet(true)
+
+			// wait until the kubelet health check will succeed
+			gomega.Eventually(ctx, func(ctx context.Context) bool {
+				return kubeletHealthCheck(kubeletHealthCheckURL)
+			}).WithTimeout(2 * time.Minute).WithPolling(5 * time.Second).Should(gomega.BeTrueBecause("expected kubelet to be in healthy state"))
+			ginkgo.By("Started the kubelet")
+
+			gomega.Consistently(ctx, func(ctx context.Context) bool {
+				return getNodeReadyStatus(ctx, f) && kubeletHealthCheck(kubeletHealthCheckURL)
+			}).WithTimeout(2 * time.Minute).WithPolling(2 * time.Second).Should(gomega.BeTrueBecause("node keeps reporting ready status"))
+		})
+	})
 })
 
 func expectFileValToEqual(filePath string, expectedValue, delta int64) error {