downwardapi.go

/*
Copyright 2015 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package downwardapi

import (
	"fmt"
	"path/filepath"

	"k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/types"
	utilerrors "k8s.io/apimachinery/pkg/util/errors"
	"k8s.io/kubernetes/pkg/api/v1/resource"
	"k8s.io/kubernetes/pkg/fieldpath"
	utilstrings "k8s.io/kubernetes/pkg/util/strings"
	"k8s.io/kubernetes/pkg/volume"
	volumeutil "k8s.io/kubernetes/pkg/volume/util"

	"k8s.io/klog"
)

// ProbeVolumePlugins is the entry point for plugin detection in a package.
func ProbeVolumePlugins() []volume.VolumePlugin {
	return []volume.VolumePlugin{&downwardAPIPlugin{}}
}

const (
	downwardAPIPluginName = "kubernetes.io/downward-api"
)

// downwardAPIPlugin implements the VolumePlugin interface.
type downwardAPIPlugin struct {
	host volume.VolumeHost
}

var _ volume.VolumePlugin = &downwardAPIPlugin{}

func wrappedVolumeSpec() volume.Spec {
	return volume.Spec{
		Volume: &v1.Volume{VolumeSource: v1.VolumeSource{EmptyDir: &v1.EmptyDirVolumeSource{Medium: v1.StorageMediumMemory}}},
	}
}

func (plugin *downwardAPIPlugin) Init(host volume.VolumeHost) error {
	plugin.host = host
	return nil
}

func (plugin *downwardAPIPlugin) GetPluginName() string {
	return downwardAPIPluginName
}

func (plugin *downwardAPIPlugin) GetVolumeName(spec *volume.Spec) (string, error) {
	volumeSource, _ := getVolumeSource(spec)
	if volumeSource == nil {
		return "", fmt.Errorf("Spec does not reference a DownwardAPI volume type")
	}

	// Return user defined volume name, since this is an ephemeral volume type
	return spec.Name(), nil
}

func (plugin *downwardAPIPlugin) CanSupport(spec *volume.Spec) bool {
	return spec.Volume != nil && spec.Volume.DownwardAPI != nil
}

func (plugin *downwardAPIPlugin) RequiresRemount() bool {
	return true
}

func (plugin *downwardAPIPlugin) SupportsMountOption() bool {
	return false
}

func (plugin *downwardAPIPlugin) SupportsBulkVolumeVerification() bool {
	return false
}

func (plugin *downwardAPIPlugin) NewMounter(spec *volume.Spec, pod *v1.Pod, opts volume.VolumeOptions) (volume.Mounter, error) {
	v := &downwardAPIVolume{
		volName: spec.Name(),
		items:   spec.Volume.DownwardAPI.Items,
		pod:     pod,
		podUID:  pod.UID,
		plugin:  plugin,
	}
	return &downwardAPIVolumeMounter{
		downwardAPIVolume: v,
		source:            *spec.Volume.DownwardAPI,
		opts:              &opts,
	}, nil
}

func (plugin *downwardAPIPlugin) NewUnmounter(volName string, podUID types.UID) (volume.Unmounter, error) {
	return &downwardAPIVolumeUnmounter{
		&downwardAPIVolume{
			volName: volName,
			podUID:  podUID,
			plugin:  plugin,
		},
	}, nil
}

func (plugin *downwardAPIPlugin) ConstructVolumeSpec(volumeName, mountPath string) (*volume.Spec, error) {
	downwardAPIVolume := &v1.Volume{
		Name: volumeName,
		VolumeSource: v1.VolumeSource{
			DownwardAPI: &v1.DownwardAPIVolumeSource{},
		},
	}
	return volume.NewSpecFromVolume(downwardAPIVolume), nil
}

// downwardAPIVolume retrieves downward API data and placing them into the volume on the host.
type downwardAPIVolume struct {
	volName string
	items   []v1.DownwardAPIVolumeFile
	pod     *v1.Pod
	podUID  types.UID // TODO: remove this redundancy as soon NewUnmounter func will have *v1.POD and not only types.UID
	plugin  *downwardAPIPlugin
	volume.MetricsNil
}

// downwardAPIVolumeMounter fetches info from downward API from the pod
// and dumps it in files
type downwardAPIVolumeMounter struct {
	*downwardAPIVolume
	source v1.DownwardAPIVolumeSource
	opts   *volume.VolumeOptions
}

// downwardAPIVolumeMounter implements volume.Mounter interface
var _ volume.Mounter = &downwardAPIVolumeMounter{}

// downward API volumes are always ReadOnlyManaged
func (d *downwardAPIVolume) GetAttributes() volume.Attributes {
	return volume.Attributes{
		ReadOnly:        true,
		Managed:         true,
		SupportsSELinux: true,
	}
}

// Checks prior to mount operations to verify that the required components (binaries, etc.)
// to mount the volume are available on the underlying node.
// If not, it returns an error
func (b *downwardAPIVolumeMounter) CanMount() error {
	return nil
}

// SetUp puts in place the volume plugin.
// This function is not idempotent by design. We want the data to be refreshed periodically.
// The internal sync interval of kubelet will drive the refresh of data.
// TODO: Add volume specific ticker and refresh loop
func (b *downwardAPIVolumeMounter) SetUp(fsGroup *int64) error {
	return b.SetUpAt(b.GetPath(), fsGroup)
}

func (b *downwardAPIVolumeMounter) SetUpAt(dir string, fsGroup *int64) error {
	klog.V(3).Infof("Setting up a downwardAPI volume %v for pod %v/%v at %v", b.volName, b.pod.Namespace, b.pod.Name, dir)
	// Wrap EmptyDir. Here we rely on the idempotency of the wrapped plugin to avoid repeatedly mounting
	wrapped, err := b.plugin.host.NewWrapperMounter(b.volName, wrappedVolumeSpec(), b.pod, *b.opts)
	if err != nil {
		klog.Errorf("Couldn't setup downwardAPI volume %v for pod %v/%v: %s", b.volName, b.pod.Namespace, b.pod.Name, err.Error())
		return err
	}

	data, err := CollectData(b.source.Items, b.pod, b.plugin.host, b.source.DefaultMode)
	if err != nil {
		klog.Errorf("Error preparing data for downwardAPI volume %v for pod %v/%v: %s", b.volName, b.pod.Namespace, b.pod.Name, err.Error())
		return err
	}

	setupSuccess := false
	if err := wrapped.SetUpAt(dir, fsGroup); err != nil {
		klog.Errorf("Unable to setup downwardAPI volume %v for pod %v/%v: %s", b.volName, b.pod.Namespace, b.pod.Name, err.Error())
		return err
	}

	if err := volumeutil.MakeNestedMountpoints(b.volName, dir, *b.pod); err != nil {
		return err
	}

	defer func() {
		// Clean up directories if setup fails
		if !setupSuccess {
			unmounter, unmountCreateErr := b.plugin.NewUnmounter(b.volName, b.podUID)
			if unmountCreateErr != nil {
				klog.Errorf("error cleaning up mount %s after failure. Create unmounter failed with %v", b.volName, unmountCreateErr)
				return
			}
			tearDownErr := unmounter.TearDown()
			if tearDownErr != nil {
				klog.Errorf("error tearing down volume %s with : %v", b.volName, tearDownErr)
			}
		}
	}()

	writerContext := fmt.Sprintf("pod %v/%v volume %v", b.pod.Namespace, b.pod.Name, b.volName)
	writer, err := volumeutil.NewAtomicWriter(dir, writerContext)
	if err != nil {
		klog.Errorf("Error creating atomic writer: %v", err)
		return err
	}

	err = writer.Write(data)
	if err != nil {
		klog.Errorf("Error writing payload to dir: %v", err)
		return err
	}

	err = volume.SetVolumeOwnership(b, fsGroup)
	if err != nil {
		klog.Errorf("Error applying volume ownership settings for group: %v", fsGroup)
		return err
	}

	setupSuccess = true
	return nil
}

// CollectData collects requested downwardAPI in data map.
// Map's key is the requested name of file to dump
// Map's value is the (sorted) content of the field to be dumped in the file.
//
// Note: this function is exported so that it can be called from the projection volume driver
func CollectData(items []v1.DownwardAPIVolumeFile, pod *v1.Pod, host volume.VolumeHost, defaultMode *int32) (map[string]volumeutil.FileProjection, error) {
	if defaultMode == nil {
		return nil, fmt.Errorf("No defaultMode used, not even the default value for it")
	}

	errlist := []error{}
	data := make(map[string]volumeutil.FileProjection)
	for _, fileInfo := range items {
		var fileProjection volumeutil.FileProjection
		fPath := filepath.Clean(fileInfo.Path)
		if fileInfo.Mode != nil {
			fileProjection.Mode = *fileInfo.Mode
		} else {
			fileProjection.Mode = *defaultMode
		}
		if fileInfo.FieldRef != nil {
			// TODO: unify with Kubelet.podFieldSelectorRuntimeValue
			if values, err := fieldpath.ExtractFieldPathAsString(pod, fileInfo.FieldRef.FieldPath); err != nil {
				klog.Errorf("Unable to extract field %s: %s", fileInfo.FieldRef.FieldPath, err.Error())
				errlist = append(errlist, err)
			} else {
				fileProjection.Data = []byte(values)
			}
		} else if fileInfo.ResourceFieldRef != nil {
			containerName := fileInfo.ResourceFieldRef.ContainerName
			nodeAllocatable, err := host.GetNodeAllocatable()
			if err != nil {
				errlist = append(errlist, err)
			} else if values, err := resource.ExtractResourceValueByContainerNameAndNodeAllocatable(fileInfo.ResourceFieldRef, pod, containerName, nodeAllocatable); err != nil {
				klog.Errorf("Unable to extract field %s: %s", fileInfo.ResourceFieldRef.Resource, err.Error())
				errlist = append(errlist, err)
			} else {
				fileProjection.Data = []byte(values)
			}
		}

		data[fPath] = fileProjection
	}
	return data, utilerrors.NewAggregate(errlist)
}

func (d *downwardAPIVolume) GetPath() string {
	return d.plugin.host.GetPodVolumeDir(d.podUID, utilstrings.EscapeQualifiedNameForDisk(downwardAPIPluginName), d.volName)
}

// downwardAPIVolumeCleaner handles cleaning up downwardAPI volumes
type downwardAPIVolumeUnmounter struct {
	*downwardAPIVolume
}

// downwardAPIVolumeUnmounter implements volume.Unmounter interface
var _ volume.Unmounter = &downwardAPIVolumeUnmounter{}

func (c *downwardAPIVolumeUnmounter) TearDown() error {
	return c.TearDownAt(c.GetPath())
}

func (c *downwardAPIVolumeUnmounter) TearDownAt(dir string) error {
	return volumeutil.UnmountViaEmptyDir(dir, c.plugin.host, c.volName, wrappedVolumeSpec(), c.podUID)
}

func getVolumeSource(spec *volume.Spec) (*v1.DownwardAPIVolumeSource, bool) {
	var readOnly bool
	var volumeSource *v1.DownwardAPIVolumeSource

	if spec.Volume != nil && spec.Volume.DownwardAPI != nil {
		volumeSource = spec.Volume.DownwardAPI
		readOnly = spec.ReadOnly
	}

	return volumeSource, readOnly
}