Windows: Fixes termination-file mounting for containerd

If Containerd is used on Windows, then we can also mount individual
files into containers (e.g.: termination-log files), which was not
possible with Docker.

Checks if the container runtime is containerd, and if it is, then also
mount the termination-log file.

pkg/kubelet/container/runtime.go

@@ -63,6 +63,9 @@ type Runtime interface {
 	// Type returns the type of the container runtime.
 	Type() string
 
+	//SupportsSingleFileMapping returns whether the container runtime supports single file mappings or not.
+	SupportsSingleFileMapping() bool
+
 	// Version returns the version information of the container runtime.
 	Version() (Version, error)
 

pkg/kubelet/container/testing/fake_runtime.go

@@ -177,6 +177,10 @@ func (f *FakeRuntime) Type() string {
 	return f.RuntimeType
 }
 
+func (f *FakeRuntime) SupportsSingleFileMapping() bool {
+	return true
+}
+
 func (f *FakeRuntime) Version() (kubecontainer.Version, error) {
 	f.Lock()
 	defer f.Unlock()

pkg/kubelet/container/testing/runtime_mock.go

@@ -47,6 +47,11 @@ func (r *Mock) Type() string {
 	return args.Get(0).(string)
 }
 
+func (r *Mock) SupportsSingleFileMapping() bool {
+	args := r.Called()
+	return args.Get(0).(bool)
+}
+
 func (r *Mock) Version() (kubecontainer.Version, error) {
 	args := r.Called()
 	return args.Get(0).(kubecontainer.Version), args.Error(1)

pkg/kubelet/kubelet_pods.go

@@ -471,9 +471,10 @@ func (kl *Kubelet) GenerateRunContainerOptions(pod *v1.Pod, container *v1.Contai
 	}
 	opts.Mounts = append(opts.Mounts, mounts...)
 
-	// Disabling adding TerminationMessagePath on Windows as these files would be mounted as docker volume and
-	// Docker for Windows has a bug where only directories can be mounted
-	if len(container.TerminationMessagePath) != 0 && runtime.GOOS != "windows" {
+	// adding TerminationMessagePath on Windows is only allowed if ContainerD is used. Individual files cannot
+	// be mounted as volumes using Docker for Windows.
+	supportsSingleFileMapping := kl.containerRuntime.SupportsSingleFileMapping()
+	if len(container.TerminationMessagePath) != 0 && supportsSingleFileMapping {
 		p := kl.getPodContainerDir(pod.UID, container.Name)
 		if err := os.MkdirAll(p, 0750); err != nil {
 			klog.Errorf("Error on creating %q: %v", p, err)

pkg/kubelet/kuberuntime/BUILD

@@ -53,6 +53,7 @@ go_library(
         "//pkg/util/parsers:go_default_library",
         "//pkg/util/selinux:go_default_library",
         "//pkg/util/tail:go_default_library",
+        "//pkg/volume/util:go_default_library",
         "//staging/src/k8s.io/api/core/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/types:go_default_library",

pkg/kubelet/kuberuntime/kuberuntime_container.go

@@ -25,6 +25,7 @@ import (
 	"net/url"
 	"os"
 	"path/filepath"
+	goruntime "runtime"
 	"sort"
 	"strings"
 	"sync"
@@ -47,6 +48,7 @@ import (
 	"k8s.io/kubernetes/pkg/kubelet/util/format"
 	"k8s.io/kubernetes/pkg/util/selinux"
 	"k8s.io/kubernetes/pkg/util/tail"
+	volumeutil "k8s.io/kubernetes/pkg/volume/util"
 )
 
 var (
@@ -292,7 +294,9 @@ func (m *kubeGenericRuntimeManager) makeMounts(opts *kubecontainer.RunContainerO
 	// The reason we create and mount the log file in here (not in kubelet) is because
 	// the file's location depends on the ID of the container, and we need to create and
 	// mount the file before actually starting the container.
-	if opts.PodContainerDir != "" && len(container.TerminationMessagePath) != 0 {
+	// we can only mount individual files (e.g.: /etc/hosts, termination-log files) on Windows only if we're using Containerd.
+	supportsSingleFileMapping := m.SupportsSingleFileMapping()
+	if opts.PodContainerDir != "" && len(container.TerminationMessagePath) != 0 && supportsSingleFileMapping {
 		// Because the PodContainerDir contains pod uid and container name which is unique enough,
 		// here we just add a random id to make the path unique for different instances
 		// of the same container.
@@ -312,10 +316,13 @@ func (m *kubeGenericRuntimeManager) makeMounts(opts *kubecontainer.RunContainerO
 				utilruntime.HandleError(fmt.Errorf("unable to set termination-log file permissions %q: %v", containerLogPath, err))
 			}
 
+			// Volume Mounts fail on Windows if it is not of the form C:/
+			containerLogPath = volumeutil.MakeAbsolutePath(goruntime.GOOS, containerLogPath)
+			terminationMessagePath := volumeutil.MakeAbsolutePath(goruntime.GOOS, container.TerminationMessagePath)
 			selinuxRelabel := selinux.SELinuxEnabled()
 			volumeMounts = append(volumeMounts, &runtimeapi.Mount{
 				HostPath:       containerLogPath,
-				ContainerPath:  container.TerminationMessagePath,
+				ContainerPath:  terminationMessagePath,
 				SelinuxRelabel: selinuxRelabel,
 			})
 		}
@@ -355,6 +362,8 @@ func getTerminationMessage(status *runtimeapi.ContainerStatus, terminationMessag
 	if len(terminationMessagePath) == 0 {
 		return "", fallbackToLogs
 	}
+	// Volume Mounts fail on Windows if it is not of the form C:/
+	terminationMessagePath = volumeutil.MakeAbsolutePath(goruntime.GOOS, terminationMessagePath)
 	for _, mount := range status.Mounts {
 		if mount.ContainerPath != terminationMessagePath {
 			continue

pkg/kubelet/kuberuntime/kuberuntime_manager.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	goruntime "runtime"
 	"time"
 
 	cadvisorapi "github.com/google/cadvisor/info/v1"
@@ -243,6 +244,17 @@ func (m *kubeGenericRuntimeManager) Type() string {
 	return m.runtimeName
 }
 
+// SupportsSingleFileMapping returns whether the container runtime supports single file mappings or not.
+// It is supported on Windows only if the container runtime is containerd.
+func (m *kubeGenericRuntimeManager) SupportsSingleFileMapping() bool {
+	switch goruntime.GOOS {
+	case "windows":
+		return m.Type() != types.DockerContainerRuntime
+	default:
+		return true
+	}
+}
+
 func newRuntimeVersion(version string) (*utilversion.Version, error) {
 	if ver, err := utilversion.ParseSemantic(version); err == nil {
 		return ver, err