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Remove sentinel file from atomic writer #22132

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merged 1 commit into from
Mar 5, 2016
Merged

Remove sentinel file from atomic writer #22132

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54 changes: 10 additions & 44 deletions pkg/volume/util/atomic_writer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -37,11 +37,7 @@ const (
)

// AtomicWriter handles atomically projecting content for a set of files into
// a target directory. AtomicWriter maintains a sentinel file named
// "..sentinel" in the target directory which is updated after new data is
// projected into the target directory, allowing consumers of the data to
// listen for updates by monitoring the sentinel file with inotify or
// fanotify.
// a target directory.
//
// Note:
//
Expand All @@ -55,6 +51,10 @@ const (
// data directory symlink are created in the writer's target dir.  This scheme
// allows the files to be atomically updated by changing the target of the
// data directory symlink.
//
// Consumers of the target directory can monitor the ..data symlink using
// inotify or fanotify to receive events when the content in the volume is
// updated.
type AtomicWriter struct {
targetDir string
logContext string
Expand All @@ -72,9 +72,8 @@ func NewAtomicWriter(targetDir, logContext string) (*AtomicWriter, error) {
}

const (
sentinelFileName = "..sentinel"
dataDirName = "..data"
newDataDirName = "..data_tmp"
dataDirName = "..data"
newDataDirName = "..data_tmp"
)

// Write does an atomic projection of the given payload into the writer's target
Expand Down Expand Up @@ -112,10 +111,8 @@ const (
// 8.  A symlink to the new timestamped directory ..data_tmp is created that will
// become the new data directory
// 9.  The new data directory symlink is renamed to the data directory; rename is atomic
// 10. The sentinel file modification and access times are updated (file is created if it does not
// already exist)
// 11. Old paths are removed from the user-visible portion of the target directory
// 12.  The previous timestamped directory is removed, if it exists
// 10. Old paths are removed from the user-visible portion of the target directory
// 11.  The previous timestamped directory is removed, if it exists
func (w *AtomicWriter) Write(payload map[string][]byte) error {
// (1)
cleanPayload, err := validatePayload(payload)
Expand Down Expand Up @@ -189,18 +186,12 @@ func (w *AtomicWriter) Write(payload map[string][]byte) error {
}

// (10)
if err = w.touchSentinelFile(); err != nil {
glog.Errorf("%s: error touching sentinel file: %v", w.logContext, err)
return err
}

// (11)
if err = w.removeUserVisiblePaths(pathsToRemove); err != nil {
glog.Errorf("%s: error removing old visible symlinks: %v", w.logContext, err)
return err
}

// (12)
// (11)
if len(oldTsDir) > 0 {
if err = os.RemoveAll(path.Join(w.targetDir, oldTsDir)); err != nil {
glog.Errorf("%s: error removing old data directory %s: %v", w.logContext, oldTsDir, err)
Expand Down Expand Up @@ -434,28 +425,3 @@ func (w *AtomicWriter) removeUserVisiblePaths(paths sets.String) error {

return nil
}

// touchSentinelFile touches the sentinel file or creates it if it doesn't exist.
func (w *AtomicWriter) touchSentinelFile() error {
sentinelFilePath := path.Join(w.targetDir, sentinelFileName)
_, err := os.Stat(sentinelFilePath)
if err != nil && os.IsNotExist(err) {
file, err := os.Create(sentinelFilePath)
if err != nil {
glog.Errorf("%s: unexpected error creating sentinel file %s: %v", w.logContext, sentinelFilePath, err)
return err
}
file.Close()
} else if err != nil {
return err
}

ts := time.Now()
err = os.Chtimes(sentinelFilePath, ts, ts)
if err != nil {
glog.Errorf("%s: error updating sentinel file mod time: %v", w.logContext, err)
return err
}

return nil
}
112 changes: 3 additions & 109 deletions pkg/volume/util/atomic_writer_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,6 @@ import (
"reflect"
"strings"
"testing"
"time"

"k8s.io/kubernetes/pkg/util/sets"
utiltesting "k8s.io/kubernetes/pkg/util/testing"
Expand Down Expand Up @@ -371,7 +370,6 @@ IAAAAAAAsDyZDwU=`
}

checkVolumeContents(targetDir, tc.name, tc.payload, t)
checkSentinelFile(targetDir, t)
}
}

Expand Down Expand Up @@ -547,8 +545,6 @@ func TestUpdate(t *testing.T) {
continue
}

oldTs := checkSentinelFile(targetDir, t)

err = writer.Write(tc.next)
if err != nil {
if tc.shouldWrite {
Expand All @@ -561,19 +557,13 @@ func TestUpdate(t *testing.T) {
}

checkVolumeContents(targetDir, tc.name, tc.next, t)

ts := checkSentinelFile(targetDir, t)
if !ts.After(oldTs) {
t.Errorf("Unexpected timestamp on sentinel file; expected %v to be after %v", ts, oldTs)
}
}
}

func TestMultipleUpdates(t *testing.T) {
cases := []struct {
name string
payloads []map[string][]byte
clearSentinel bool
name string
payloads []map[string][]byte
}{
{
name: "update 1",
Expand Down Expand Up @@ -625,7 +615,6 @@ func TestMultipleUpdates(t *testing.T) {
"bar": []byte("bar4"),
},
},
clearSentinel: true,
},
{
name: "subdirectories 2",
Expand Down Expand Up @@ -710,84 +699,12 @@ func TestMultipleUpdates(t *testing.T) {
continue
}

var oldTs *time.Time = nil
writer := &AtomicWriter{targetDir: targetDir, logContext: "-test-"}

for ii, payload := range tc.payloads {
for _, payload := range tc.payloads {
writer.Write(payload)

checkVolumeContents(targetDir, tc.name, payload, t)
ts := checkSentinelFile(targetDir, t)

if oldTs != nil && !ts.After(*oldTs) {
t.Errorf("%v[%v] unexpected timestamp on sentinel file; expected %v to be after %v", tc.name, ii, ts, oldTs)
}
oldTs = &ts

if tc.clearSentinel {
clearSentinelFile(targetDir, t)
}
}
}
}

func TestSentinelFileModTimeIncreasing(t *testing.T) {
cases := []struct {
name string
iterations int
clearSentinelFile bool
}{
{
name: "5 iters",
iterations: 5,
},
{
name: "50 iters",
iterations: 50,
},
{
name: "1000 iters",
iterations: 1000,
},
{
name: "1000 clear sentinel",
iterations: 1000,
clearSentinelFile: true,
},
{
name: "10000 clear sentinel",
iterations: 10000,
clearSentinelFile: true,
},
}

for _, tc := range cases {
targetDir, err := utiltesting.MkTmpdir("atomic-write")
if err != nil {
t.Errorf("%v: unexpected error creating tmp dir: %v", tc.name, err)
continue
}

var oldTs *time.Time = nil
writer := &AtomicWriter{targetDir: targetDir, logContext: "-test-"}

for i := 0; i < tc.iterations; i++ {
err = writer.touchSentinelFile()
if err != nil {
t.Errorf("%v: unexpected error touching sentinel file: %v", tc.name, err)
continue
}

ts := checkSentinelFile(targetDir, t)
if oldTs != nil && !ts.After(*oldTs) {
t.Errorf("%v: unexpected timestamp on sentinel file; expected %v to be after %v", tc.name, ts, oldTs)
continue
}
oldTs = &ts

if tc.clearSentinelFile {
clearSentinelFile(targetDir, t)
}
}
}
}
Expand Down Expand Up @@ -829,26 +746,3 @@ func checkVolumeContents(targetDir, tcName string, payload map[string][]byte, t
t.Errorf("%v: payload and observed payload do not match.", tcName)
}
}

func checkSentinelFile(targetDir string, t *testing.T) time.Time {
sentinelFilePath := filepath.Join(targetDir, sentinelFileName)
info, err := os.Stat(sentinelFilePath)
if err != nil {
t.Errorf("Couldn't stat sentinel file for dir %v: %v", targetDir, err)
return time.Now()
}

return info.ModTime()
}

func clearSentinelFile(targetDir string, t *testing.T) {
sentinelFilePath := filepath.Join(targetDir, sentinelFileName)
_, err := os.Stat(sentinelFilePath)
if err != nil {
t.Errorf("Couldn't stat sentinel file for dir %v: %v", targetDir, err)
}
err = os.Remove(sentinelFilePath)
if err != nil {
t.Errorf("Error removing sentinel file: %v", err)
}
}