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Refactor downward API volume to use AtomicWriter #24625

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merged 1 commit into from
May 14, 2016
Merged

Refactor downward API volume to use AtomicWriter #24625

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188 changes: 14 additions & 174 deletions pkg/volume/downwardapi/downwardapi.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,20 +17,18 @@ limitations under the License.
package downwardapi

import (
"io/ioutil"
"os"
"fmt"
"path"
"path/filepath"
"sort"
"strings"
"time"

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

"github.com/golang/glog"
)
Expand Down Expand Up @@ -151,18 +149,19 @@ func (b *downwardAPIVolumeMounter) SetUpAt(dir string, fsGroup *int64) error {
return err
}

if !b.isDataChanged(data) {
// No data changed: nothing to write
return nil
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 {
glog.Errorf("Error creating atomic writer: %v", err)
return err
}

if err := b.writeData(data); err != nil {
glog.Errorf("Unable to dump files for downwardAPI volume %v for pod %v/%v: %s", b.volName, b.pod.Namespace, b.pod.Name, err.Error())
err = writer.Write(data)
if err != nil {
glog.Errorf("Error writing payload to dir: %v", err)
return err
}

glog.V(3).Infof("Data dumped for downwardAPI volume %v for pod %v/%v", b.volName, b.pod.Namespace, b.pod.Name)

volume.SetVolumeOwnership(b, fsGroup)

return nil
Expand All @@ -171,179 +170,20 @@ func (b *downwardAPIVolumeMounter) SetUpAt(dir string, fsGroup *int64) error {
// 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.
func (d *downwardAPIVolume) collectData() (map[string]string, error) {
func (d *downwardAPIVolume) collectData() (map[string][]byte, error) {
errlist := []error{}
data := make(map[string]string)
data := make(map[string][]byte)
for fieldReference, fileName := range d.fieldReferenceFileNames {
if values, err := fieldpath.ExtractFieldPathAsString(d.pod, fieldReference); err != nil {
glog.Errorf("Unable to extract field %s: %s", fieldReference, err.Error())
errlist = append(errlist, err)
} else {
data[fileName] = sortLines(values)
data[fileName] = []byte(sortLines(values))
}
}
return data, utilerrors.NewAggregate(errlist)
}

// isDataChanged iterate over all the entries to check whether at least one
// file needs to be updated.
func (d *downwardAPIVolume) isDataChanged(data map[string]string) bool {
for fileName, values := range data {
if isFileToGenerate(path.Join(d.GetPath(), fileName), values) {
return true
}
}
return false
}

// isFileToGenerate compares actual file with the new values. If
// different (or the file does not exist) return true
func isFileToGenerate(fileName, values string) bool {
if _, err := os.Lstat(fileName); os.IsNotExist(err) {
return true
}
return readFile(fileName) != values
}

const (
downwardAPIDir = "..downwardapi"
downwardAPITmpDir = "..downwardapi_tmp"
// It seems reasonable to allow dot-files in the config, so we reserved double-dot-files for the implementation".
)

// writeData writes requested downwardAPI in specified files.
//
// The file visible in this volume are symlinks to files in the '..downwardapi'
// directory. Actual files are stored in an hidden timestamped directory which is
// symlinked to by '..downwardapi'. The timestamped directory and '..downwardapi' symlink
// are created in the plugin root dir.  This scheme allows the files to be
// atomically updated by changing the target of the '..downwardapi' symlink.  When new
// data is available:
//
// 1.  A new timestamped dir is created by writeDataInTimestampDir and requested data
// is written inside new timestamped directory
// 2.  Symlinks and directory for new files are created (if needed).
// For example for files:
// <volume-dir>/user_space/labels
// <volume-dir>/k8s_space/annotations
// <volume-dir>/podName
// This structure is created:
// <volume-dir>/podName -> ..downwardapi/podName
// <volume-dir>/user_space/labels -> ../..downwardapi/user_space/labels
// <volume-dir>/k8s_space/annotations -> ../..downwardapi/k8s_space/annotations
// <volume-dir>/..downwardapi -> ..downwardapi.12345678
// where ..downwardapi.12345678 is a randomly generated directory which contains
// the real data. If a file has to be dumped in subdirectory (for example <volume-dir>/user_space/labels)
// plugin builds a relative symlink (<volume-dir>/user_space/labels -> ../..downwardapi/user_space/labels)
// 3.  The previous timestamped directory is detected reading the '..downwardapi' symlink
// 4.  In case no symlink exists then it's created
// 5.  In case symlink exists a new temporary symlink is created ..downwardapi_tmp
// 6.  ..downwardapi_tmp is renamed to ..downwardapi
// 7.  The previous timestamped directory is removed

func (d *downwardAPIVolume) writeData(data map[string]string) error {
timestampDir, err := d.writeDataInTimestampDir(data)
if err != nil {
glog.Errorf("Unable to write data in temporary directory: %s", err.Error())
return err
}
// update symbolic links for relative paths
if err = d.updateSymlinksToCurrentDir(); err != nil {
os.RemoveAll(timestampDir)
glog.Errorf("Unable to create symlinks and/or directory: %s", err.Error())
return err
}

_, timestampDirBaseName := filepath.Split(timestampDir)
var oldTimestampDirectory string
oldTimestampDirectory, err = os.Readlink(path.Join(d.GetPath(), downwardAPIDir))

if err = os.Symlink(timestampDirBaseName, path.Join(d.GetPath(), downwardAPITmpDir)); err != nil {
os.RemoveAll(timestampDir)
glog.Errorf("Unable to create symolic link: %s", err.Error())
return err
}

// Rename the symbolic link downwardAPITmpDir to downwardAPIDir
if err = os.Rename(path.Join(d.GetPath(), downwardAPITmpDir), path.Join(d.GetPath(), downwardAPIDir)); err != nil {
// in case of error remove latest data and downwardAPITmpDir
os.Remove(path.Join(d.GetPath(), downwardAPITmpDir))
os.RemoveAll(timestampDir)
glog.Errorf("Unable to rename symbolic link: %s", err.Error())
return err
}
// Remove oldTimestampDirectory
if len(oldTimestampDirectory) > 0 {
if err := os.RemoveAll(path.Join(d.GetPath(), oldTimestampDirectory)); err != nil {
glog.Errorf("Unable to remove directory: %s", err.Error())
return err
}
}
return nil
}

// writeDataInTimestampDir writes the latest data into a new temporary directory with a timestamp.
func (d *downwardAPIVolume) writeDataInTimestampDir(data map[string]string) (string, error) {
errlist := []error{}
timestampDir, err := ioutil.TempDir(d.GetPath(), ".."+time.Now().Format("2006_01_02_15_04_05"))
for fileName, values := range data {
fullPathFile := path.Join(timestampDir, fileName)
dir, _ := filepath.Split(fullPathFile)
if err = os.MkdirAll(dir, os.ModePerm); err != nil {
glog.Errorf("Unable to create directory `%s`: %s", dir, err.Error())
return "", err
}
if err := ioutil.WriteFile(fullPathFile, []byte(values), 0644); err != nil {
glog.Errorf("Unable to write file `%s`: %s", fullPathFile, err.Error())
errlist = append(errlist, err)
}
}
return timestampDir, utilerrors.NewAggregate(errlist)
}

// updateSymlinksToCurrentDir creates the relative symlinks for all the files configured in this volume.
// If the directory in a file path does not exist, it is created.
//
// For example for files: "bar", "foo/bar", "baz/bar", "foo/baz/blah"
// the following symlinks and subdirectory are created:
// bar -> ..downwardapi/bar
// baz/bar -> ../..downwardapi/baz/bar
// foo/bar -> ../..downwardapi/foo/bar
// foo/baz/blah -> ../../..downwardapi/foo/baz/blah
func (d *downwardAPIVolume) updateSymlinksToCurrentDir() error {
for _, f := range d.fieldReferenceFileNames {
dir, _ := filepath.Split(f)
nbOfSubdir := 0
if len(dir) > 0 {
// if dir is not empty f contains at least a subdirectory (for example: f="foo/bar")
// since filepath.Split leaves a trailing '/' we have dir="foo/"
// and since len(strings.Split"foo/")=2 to count the number
// of sub directory you need to remove 1
nbOfSubdir = len(strings.Split(dir, "/")) - 1
if err := os.MkdirAll(path.Join(d.GetPath(), dir), os.ModePerm); err != nil {
return err
}
}
if _, err := os.Readlink(path.Join(d.GetPath(), f)); err != nil {
// link does not exist create it
presentedFile := path.Join(strings.Repeat("../", nbOfSubdir), downwardAPIDir, f)
actualFile := path.Join(d.GetPath(), f)
if err := os.Symlink(presentedFile, actualFile); err != nil {
return err
}
}
}
return nil
}

// readFile reads the file at the given path and returns the content as a string.
func readFile(path string) string {
if data, err := ioutil.ReadFile(path); err == nil {
return string(data)
}
return ""
}

// sortLines sorts the strings generated from map based data
// (annotations and labels)
func sortLines(values string) string {
Expand All @@ -356,7 +196,7 @@ func (d *downwardAPIVolume) GetPath() string {
return d.plugin.host.GetPodVolumeDir(d.podUID, utilstrings.EscapeQualifiedNameForDisk(downwardAPIPluginName), d.volName)
}

// downwardAPIVolumeCleander handles cleaning up downwardAPI volumes
// downwardAPIVolumeCleaner handles cleaning up downwardAPI volumes
type downwardAPIVolumeUnmounter struct {
*downwardAPIVolume
}
Expand Down
6 changes: 4 additions & 2 deletions pkg/volume/downwardapi/downwardapi_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,8 @@ import (
volumetest "k8s.io/kubernetes/pkg/volume/testing"
)

const downwardAPIDir = "..data"

func formatMap(m map[string]string) (fmtstr string) {
for key, value := range m {
fmtstr += fmt.Sprintf("%v=%q\n", key, value)
Expand Down Expand Up @@ -407,7 +409,7 @@ func TestWriteTwiceNoUpdate(t *testing.T) {
// get the link of the link
var currentTarget string
if currentTarget, err = os.Readlink(path.Join(volumePath, downwardAPIDir)); err != nil {
t.Errorf(".current should be a link... %s\n", err.Error())
t.Errorf(".data should be a link... %s\n", err.Error())
}

err = mounter.SetUp(nil) // now re-run Setup
Expand All @@ -418,7 +420,7 @@ func TestWriteTwiceNoUpdate(t *testing.T) {
// get the link of the link
var currentTarget2 string
if currentTarget2, err = os.Readlink(path.Join(volumePath, downwardAPIDir)); err != nil {
t.Errorf(".current should be a link... %s\n", err.Error())
t.Errorf(".data should be a link... %s\n", err.Error())
}

if currentTarget2 != currentTarget {
Expand Down