Merge pull request #31996 from mtaufen/detect-swap-enabled

Automatic merge from submit-queue

Fail kubelet creation if swap enabled and configured with memory eviction thresholds

/cc @vishh @derekwaynecarr

**Release note**:

```
This adds an opt-in Kubelet flag (--fail-swap-on) that causes the Kubelet to fail to start if swap is enabled on the node. This is a temporary opt-in, and the Kubelet will by default fail with swap enabled starting in 1.6.0. The KubeletConfiguration equivalent to the flag is FailSwapOn.
```

cmd/kubelet/app/options/options.go

@@ -78,6 +78,9 @@ func NewKubeletServer() *KubeletServer {
 
 // AddFlags adds flags for a specific KubeletServer to the specified FlagSet
 func (s *KubeletServer) AddFlags(fs *pflag.FlagSet) {
+	// TODO(#34726:1.8.0): Remove the opt-in for failing when swap is enabled.
+	fs.BoolVar(&s.ExperimentalFailSwapOn, "experimental-fail-swap-on", s.ExperimentalFailSwapOn, "Makes the Kubelet fail to start if swap is enabled on the node. This is a temporary opton to maintain legacy behavior, failing due to swap enabled will happen by default in v1.6.")
+
 	fs.Var(&s.KubeConfig, "kubeconfig", "Path to a kubeconfig file, specifying how to connect to the API server. --api-servers will be used for the location unless --require-kubeconfig is set.")
 	fs.BoolVar(&s.RequireKubeConfig, "require-kubeconfig", s.RequireKubeConfig, "If true the Kubelet will exit if there are configuration errors, and will ignore the value of --api-servers in favor of the server defined in the kubeconfig file.")
 

cmd/kubelet/app/server.go

@@ -434,17 +434,22 @@ func run(s *options.KubeletServer, kubeDeps *kubelet.KubeletDeps) (err error) {
 		if s.SystemCgroups != "" && s.CgroupRoot == "" {
 			return fmt.Errorf("invalid configuration: system container was specified and cgroup root was not specified")
 		}
-		kubeDeps.ContainerManager, err = cm.NewContainerManager(kubeDeps.Mounter, kubeDeps.CAdvisorInterface, cm.NodeConfig{
-			RuntimeCgroupsName:    s.RuntimeCgroups,
-			SystemCgroupsName:     s.SystemCgroups,
-			KubeletCgroupsName:    s.KubeletCgroups,
-			ContainerRuntime:      s.ContainerRuntime,
-			CgroupsPerQOS:         s.CgroupsPerQOS,
-			CgroupRoot:            s.CgroupRoot,
-			CgroupDriver:          s.CgroupDriver,
-			ProtectKernelDefaults: s.ProtectKernelDefaults,
-			EnableCRI:             s.EnableCRI,
-		})
+		kubeDeps.ContainerManager, err = cm.NewContainerManager(
+			kubeDeps.Mounter,
+			kubeDeps.CAdvisorInterface,
+			cm.NodeConfig{
+				RuntimeCgroupsName:    s.RuntimeCgroups,
+				SystemCgroupsName:     s.SystemCgroups,
+				KubeletCgroupsName:    s.KubeletCgroups,
+				ContainerRuntime:      s.ContainerRuntime,
+				CgroupsPerQOS:         s.CgroupsPerQOS,
+				CgroupRoot:            s.CgroupRoot,
+				CgroupDriver:          s.CgroupDriver,
+				ProtectKernelDefaults: s.ProtectKernelDefaults,
+				EnableCRI:             s.EnableCRI,
+			},
+			s.ExperimentalFailSwapOn)
+
 		if err != nil {
 			return err
 		}

hack/verify-flags/known-flags.txt

@@ -202,6 +202,7 @@ external-etcd-keyfile
 external-hostname
 external-ip
 extra-peer-dirs
+experimental-fail-swap-on
 failover-timeout
 failure-domains
 fake-clientset

pkg/apis/componentconfig/types.go

@@ -465,6 +465,9 @@ type KubeletConfiguration struct {
 	// Enable Container Runtime Interface (CRI) integration.
 	// +optional
 	EnableCRI bool `json:"enableCRI,omitempty"`
+	// TODO(#34726:1.8.0): Remove the opt-in for failing when swap is enabled.
+	// Tells the Kubelet to fail to start if swap is enabled on the node.
+	ExperimentalFailSwapOn bool `json:"experimentalFailSwapOn,omitempty"`
 }
 
 type KubeletAuthorizationMode string

pkg/apis/componentconfig/v1alpha1/types.go

@@ -504,6 +504,9 @@ type KubeletConfiguration struct {
 	// Enable Container Runtime Interface (CRI) integration.
 	// +optional
 	EnableCRI bool `json:"enableCRI,omitempty"`
+	// TODO(#34726:1.8.0): Remove the opt-in for failing when swap is enabled.
+	// Tells the Kubelet to fail to start if swap is enabled on the node.
+	ExperimentalFailSwapOn bool `json:"experimentalFailSwapOn,omitempty"`
 }
 
 type KubeletAuthorizationMode string

pkg/apis/componentconfig/v1alpha1/zz_generated.conversion.go

@@ -407,6 +407,7 @@ func autoConvert_v1alpha1_KubeletConfiguration_To_componentconfig_KubeletConfigu
 	out.AllowedUnsafeSysctls = *(*[]string)(unsafe.Pointer(&in.AllowedUnsafeSysctls))
 	out.FeatureGates = in.FeatureGates
 	out.EnableCRI = in.EnableCRI
+	out.ExperimentalFailSwapOn = in.ExperimentalFailSwapOn
 	return nil
 }
 
@@ -575,6 +576,7 @@ func autoConvert_componentconfig_KubeletConfiguration_To_v1alpha1_KubeletConfigu
 	out.AllowedUnsafeSysctls = *(*[]string)(unsafe.Pointer(&in.AllowedUnsafeSysctls))
 	out.FeatureGates = in.FeatureGates
 	out.EnableCRI = in.EnableCRI
+	out.ExperimentalFailSwapOn = in.ExperimentalFailSwapOn
 	return nil
 }
 

pkg/apis/componentconfig/v1alpha1/zz_generated.deepcopy.go

@@ -461,6 +461,7 @@ func DeepCopy_v1alpha1_KubeletConfiguration(in interface{}, out interface{}, c *
 		}
 		out.FeatureGates = in.FeatureGates
 		out.EnableCRI = in.EnableCRI
+		out.ExperimentalFailSwapOn = in.ExperimentalFailSwapOn
 		return nil
 	}
 }

pkg/apis/componentconfig/zz_generated.deepcopy.go

@@ -392,6 +392,7 @@ func DeepCopy_componentconfig_KubeletConfiguration(in interface{}, out interface
 		}
 		out.FeatureGates = in.FeatureGates
 		out.EnableCRI = in.EnableCRI
+		out.ExperimentalFailSwapOn = in.ExperimentalFailSwapOn
 		return nil
 	}
 }

pkg/generated/openapi/zz_generated.openapi.go

@@ -3003,8 +3003,15 @@ var OpenAPIDefinitions *common.OpenAPIDefinitions = &common.OpenAPIDefinitions{
 							Format:      "",
 						},
 					},
+					"experimentalFailSwapOn": {
+						SchemaProps: spec.SchemaProps{
+							Description: "Tells the Kubelet to fail to start if swap is enabled on the node.",
+							Type:        []string{"boolean"},
+							Format:      "",
+						},
+					},
 				},
-				Required: []string{"TypeMeta", "podManifestPath", "syncFrequency", "fileCheckFrequency", "httpCheckFrequency", "manifestURL", "manifestURLHeader", "enableServer", "address", "port", "readOnlyPort", "tlsCertFile", "tlsPrivateKeyFile", "certDirectory", "authentication", "authorization", "hostnameOverride", "podInfraContainerImage", "dockerEndpoint", "rootDirectory", "seccompProfileRoot", "allowPrivileged", "hostNetworkSources", "hostPIDSources", "hostIPCSources", "registryPullQPS", "registryBurst", "eventRecordQPS", "eventBurst", "enableDebuggingHandlers", "minimumGCAge", "maxPerPodContainerCount", "maxContainerCount", "cAdvisorPort", "healthzPort", "healthzBindAddress", "oomScoreAdj", "registerNode", "clusterDomain", "masterServiceNamespace", "clusterDNS", "streamingConnectionIdleTimeout", "nodeStatusUpdateFrequency", "imageMinimumGCAge", "imageGCHighThresholdPercent", "imageGCLowThresholdPercent", "lowDiskSpaceThresholdMB", "volumeStatsAggPeriod", "networkPluginName", "networkPluginMTU", "networkPluginDir", "cniConfDir", "cniBinDir", "volumePluginDir", "containerRuntime", "remoteRuntimeEndpoint", "remoteImageEndpoint", "experimentalMounterPath", "experimentalMounterRootfsPath", "lockFilePath", "exitOnLockContention", "hairpinMode", "babysitDaemons", "maxPods", "nvidiaGPUs", "dockerExecHandlerName", "podCIDR", "resolvConf", "cpuCFSQuota", "containerized", "maxOpenFiles", "reconcileCIDR", "registerSchedulable", "contentType", "kubeAPIQPS", "kubeAPIBurst", "serializeImagePulls", "nodeLabels", "nonMasqueradeCIDR", "enableCustomMetrics", "podsPerCore", "enableControllerAttachDetach", "systemReserved", "kubeReserved", "protectKernelDefaults", "makeIPTablesUtilChains", "iptablesMasqueradeBit", "iptablesDropBit", "featureGates"},
+				Required: []string{"TypeMeta", "podManifestPath", "syncFrequency", "fileCheckFrequency", "httpCheckFrequency", "manifestURL", "manifestURLHeader", "enableServer", "address", "port", "readOnlyPort", "tlsCertFile", "tlsPrivateKeyFile", "certDirectory", "authentication", "authorization", "hostnameOverride", "podInfraContainerImage", "dockerEndpoint", "rootDirectory", "seccompProfileRoot", "allowPrivileged", "hostNetworkSources", "hostPIDSources", "hostIPCSources", "registryPullQPS", "registryBurst", "eventRecordQPS", "eventBurst", "enableDebuggingHandlers", "minimumGCAge", "maxPerPodContainerCount", "maxContainerCount", "cAdvisorPort", "healthzPort", "healthzBindAddress", "oomScoreAdj", "registerNode", "clusterDomain", "masterServiceNamespace", "clusterDNS", "streamingConnectionIdleTimeout", "nodeStatusUpdateFrequency", "imageMinimumGCAge", "imageGCHighThresholdPercent", "imageGCLowThresholdPercent", "lowDiskSpaceThresholdMB", "volumeStatsAggPeriod", "networkPluginName", "networkPluginMTU", "networkPluginDir", "cniConfDir", "cniBinDir", "volumePluginDir", "containerRuntime", "remoteRuntimeEndpoint", "remoteImageEndpoint", "experimentalMounterPath", "experimentalMounterRootfsPath", "lockFilePath", "exitOnLockContention", "hairpinMode", "babysitDaemons", "maxPods", "nvidiaGPUs", "dockerExecHandlerName", "podCIDR", "resolvConf", "cpuCFSQuota", "containerized", "maxOpenFiles", "reconcileCIDR", "registerSchedulable", "contentType", "kubeAPIQPS", "kubeAPIBurst", "serializeImagePulls", "nodeLabels", "nonMasqueradeCIDR", "enableCustomMetrics", "podsPerCore", "enableControllerAttachDetach", "systemReserved", "kubeReserved", "protectKernelDefaults", "makeIPTablesUtilChains", "iptablesMasqueradeBit", "iptablesDropBit", "featureGates", "experimentalFailSwapOn"},
 			},
 		},
 		Dependencies: []string{
@@ -14757,8 +14764,15 @@ var OpenAPIDefinitions *common.OpenAPIDefinitions = &common.OpenAPIDefinitions{
 							Format:      "",
 						},
 					},
+					"experimentalFailSwapOn": {
+						SchemaProps: spec.SchemaProps{
+							Description: "Tells the Kubelet to fail to start if swap is enabled on the node.",
+							Type:        []string{"boolean"},
+							Format:      "",
+						},
+					},
 				},
-				Required: []string{"TypeMeta", "podManifestPath", "syncFrequency", "fileCheckFrequency", "httpCheckFrequency", "manifestURL", "manifestURLHeader", "enableServer", "address", "port", "readOnlyPort", "tlsCertFile", "tlsPrivateKeyFile", "certDirectory", "authentication", "authorization", "hostnameOverride", "podInfraContainerImage", "dockerEndpoint", "rootDirectory", "seccompProfileRoot", "allowPrivileged", "hostNetworkSources", "hostPIDSources", "hostIPCSources", "registryPullQPS", "registryBurst", "eventRecordQPS", "eventBurst", "enableDebuggingHandlers", "minimumGCAge", "maxPerPodContainerCount", "maxContainerCount", "cAdvisorPort", "healthzPort", "healthzBindAddress", "oomScoreAdj", "registerNode", "clusterDomain", "masterServiceNamespace", "clusterDNS", "streamingConnectionIdleTimeout", "nodeStatusUpdateFrequency", "imageMinimumGCAge", "imageGCHighThresholdPercent", "imageGCLowThresholdPercent", "lowDiskSpaceThresholdMB", "volumeStatsAggPeriod", "networkPluginName", "networkPluginDir", "cniConfDir", "cniBinDir", "networkPluginMTU", "volumePluginDir", "cloudProvider", "cloudConfigFile", "kubeletCgroups", "runtimeCgroups", "systemCgroups", "cgroupRoot", "containerRuntime", "remoteRuntimeEndpoint", "remoteImageEndpoint", "runtimeRequestTimeout", "rktPath", "experimentalMounterPath", "experimentalMounterRootfsPath", "rktAPIEndpoint", "rktStage1Image", "lockFilePath", "exitOnLockContention", "hairpinMode", "babysitDaemons", "maxPods", "nvidiaGPUs", "dockerExecHandlerName", "podCIDR", "resolvConf", "cpuCFSQuota", "containerized", "maxOpenFiles", "reconcileCIDR", "registerSchedulable", "contentType", "kubeAPIQPS", "kubeAPIBurst", "serializeImagePulls", "outOfDiskTransitionFrequency", "nodeIP", "nodeLabels", "nonMasqueradeCIDR", "enableCustomMetrics", "evictionHard", "evictionSoft", "evictionSoftGracePeriod", "evictionPressureTransitionPeriod", "evictionMaxPodGracePeriod", "evictionMinimumReclaim", "podsPerCore", "enableControllerAttachDetach", "systemReserved", "kubeReserved", "protectKernelDefaults", "makeIPTablesUtilChains", "iptablesMasqueradeBit", "iptablesDropBit", "featureGates"},
+				Required: []string{"TypeMeta", "podManifestPath", "syncFrequency", "fileCheckFrequency", "httpCheckFrequency", "manifestURL", "manifestURLHeader", "enableServer", "address", "port", "readOnlyPort", "tlsCertFile", "tlsPrivateKeyFile", "certDirectory", "authentication", "authorization", "hostnameOverride", "podInfraContainerImage", "dockerEndpoint", "rootDirectory", "seccompProfileRoot", "allowPrivileged", "hostNetworkSources", "hostPIDSources", "hostIPCSources", "registryPullQPS", "registryBurst", "eventRecordQPS", "eventBurst", "enableDebuggingHandlers", "minimumGCAge", "maxPerPodContainerCount", "maxContainerCount", "cAdvisorPort", "healthzPort", "healthzBindAddress", "oomScoreAdj", "registerNode", "clusterDomain", "masterServiceNamespace", "clusterDNS", "streamingConnectionIdleTimeout", "nodeStatusUpdateFrequency", "imageMinimumGCAge", "imageGCHighThresholdPercent", "imageGCLowThresholdPercent", "lowDiskSpaceThresholdMB", "volumeStatsAggPeriod", "networkPluginName", "networkPluginDir", "cniConfDir", "cniBinDir", "networkPluginMTU", "volumePluginDir", "cloudProvider", "cloudConfigFile", "kubeletCgroups", "runtimeCgroups", "systemCgroups", "cgroupRoot", "containerRuntime", "remoteRuntimeEndpoint", "remoteImageEndpoint", "runtimeRequestTimeout", "rktPath", "experimentalMounterPath", "experimentalMounterRootfsPath", "rktAPIEndpoint", "rktStage1Image", "lockFilePath", "exitOnLockContention", "hairpinMode", "babysitDaemons", "maxPods", "nvidiaGPUs", "dockerExecHandlerName", "podCIDR", "resolvConf", "cpuCFSQuota", "containerized", "maxOpenFiles", "reconcileCIDR", "registerSchedulable", "contentType", "kubeAPIQPS", "kubeAPIBurst", "serializeImagePulls", "outOfDiskTransitionFrequency", "nodeIP", "nodeLabels", "nonMasqueradeCIDR", "enableCustomMetrics", "evictionHard", "evictionSoft", "evictionSoftGracePeriod", "evictionPressureTransitionPeriod", "evictionMaxPodGracePeriod", "evictionMinimumReclaim", "podsPerCore", "enableControllerAttachDetach", "systemReserved", "kubeReserved", "protectKernelDefaults", "makeIPTablesUtilChains", "iptablesMasqueradeBit", "iptablesDropBit", "featureGates", "experimentalFailSwapOn"},
 			},
 		},
 		Dependencies: []string{

pkg/kubelet/cm/container_manager_linux.go

@@ -19,9 +19,11 @@ limitations under the License.
 package cm
 
 import (
+	"bufio"
 	"fmt"
 	"io/ioutil"
 	"os"
+	"os/exec"
 	"path"
 	"strconv"
 	"sync"
@@ -164,12 +166,44 @@ func validateSystemRequirements(mountUtil mount.Interface) (features, error) {
 // TODO(vmarmol): Add limits to the system containers.
 // Takes the absolute name of the specified containers.
 // Empty container name disables use of the specified container.
-func NewContainerManager(mountUtil mount.Interface, cadvisorInterface cadvisor.Interface, nodeConfig NodeConfig) (ContainerManager, error) {
+func NewContainerManager(mountUtil mount.Interface, cadvisorInterface cadvisor.Interface, nodeConfig NodeConfig, failSwapOn bool) (ContainerManager, error) {
 	subsystems, err := GetCgroupSubsystems()
 	if err != nil {
 		return nil, fmt.Errorf("failed to get mounted cgroup subsystems: %v", err)
 	}
 
+	// Check whether swap is enabled. The Kubelet does not support running with swap enabled.
+	cmd := exec.Command("cat", "/proc/swaps")
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, err
+	}
+	if err := cmd.Start(); err != nil {
+		return nil, err
+	}
+	var buf []string
+	scanner := bufio.NewScanner(stdout)
+	for scanner.Scan() { // Splits on newlines by default
+		buf = append(buf, scanner.Text())
+	}
+	if err := cmd.Wait(); err != nil { // Clean up
+		return nil, err
+	}
+
+	// TODO(#34726:1.8.0): Remove the opt-in for failing when swap is enabled.
+	//     Running with swap enabled should be considered an error, but in order to maintain legacy
+	//     behavior we have to require an opt-in to this error for a period of time.
+
+	// If there is more than one line (table headers) in /proc/swaps, swap is enabled and we should error out.
+	if len(buf) > 1 {
+		if failSwapOn {
+			return nil, fmt.Errorf("Running with swap on is not supported, please disable swap! /proc/swaps contained: %v", buf)
+		}
+		glog.Warningf("Running with swap on is not supported, please disable swap! " +
+			"This will be a fatal error by default starting in K8s v1.6! " +
+			"In the meantime, you can opt-in to making this a fatal error by enabling --experimental-fail-swap-on.")
+	}
+
 	// Check if Cgroup-root actually exists on the node
 	if nodeConfig.CgroupsPerQOS {
 		// this does default to / when enabled, but this tests against regressions.