Merge pull request #171 from tendermint/feature/xla-writefileatomic
Simplify WriteFileAtomic
This commit is contained in:
commit
a86b1d8f75
44
common/os.go
44
common/os.go
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@ -124,32 +124,32 @@ func MustWriteFile(filePath string, contents []byte, mode os.FileMode) {
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}
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}
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// WriteFileAtomic writes newBytes to temp and atomically moves to filePath
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// when everything else succeeds.
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func WriteFileAtomic(filePath string, newBytes []byte, mode os.FileMode) error {
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dir := filepath.Dir(filePath)
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f, err := ioutil.TempFile(dir, "")
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// WriteFileAtomic creates a temporary file with data and the perm given and
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// swaps it atomically with filename if successful.
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func WriteFileAtomic(filename string, data []byte, perm os.FileMode) error {
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var (
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dir = filepath.Dir(filename)
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tempFile = filepath.Join(dir, "write-file-atomic-"+RandStr(32))
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// Override in case it does exist, create in case it doesn't and force kernel
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// flush, which still leaves the potential of lingering disk cache.
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flag = os.O_WRONLY | os.O_CREATE | os.O_SYNC | os.O_TRUNC
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)
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f, err := os.OpenFile(tempFile, flag, perm)
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if err != nil {
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return err
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}
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_, err = f.Write(newBytes)
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if err == nil {
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err = f.Sync()
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// Clean up in any case. Defer stacking order is last-in-first-out.
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defer os.Remove(f.Name())
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defer f.Close()
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if n, err := f.Write(data); err != nil {
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return err
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} else if n < len(data) {
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return io.ErrShortWrite
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}
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if closeErr := f.Close(); err == nil {
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err = closeErr
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}
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if permErr := os.Chmod(f.Name(), mode); err == nil {
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err = permErr
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}
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if err == nil {
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err = os.Rename(f.Name(), filePath)
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}
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// any err should result in full cleanup
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if err != nil {
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os.Remove(f.Name())
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}
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return err
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return os.Rename(f.Name(), filename)
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}
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//--------------------------------------------------------------------------------
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@ -2,30 +2,52 @@ package common
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import (
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"bytes"
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"fmt"
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"io/ioutil"
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"math/rand"
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"os"
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"testing"
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"time"
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)
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func TestWriteFileAtomic(t *testing.T) {
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data := []byte("Becatron")
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fname := fmt.Sprintf("/tmp/write-file-atomic-test-%v.txt", time.Now().UnixNano())
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err := WriteFileAtomic(fname, data, 0664)
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var (
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seed = rand.New(rand.NewSource(time.Now().UnixNano()))
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data = []byte(RandStr(seed.Intn(2048)))
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old = RandBytes(seed.Intn(2048))
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perm os.FileMode = 0600
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)
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f, err := ioutil.TempFile("/tmp", "write-atomic-test-")
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if err != nil {
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t.Fatal(err)
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}
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rData, err := ioutil.ReadFile(fname)
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defer os.Remove(f.Name())
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if err := ioutil.WriteFile(f.Name(), old, 0664); err != nil {
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t.Fatal(err)
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}
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if err := WriteFileAtomic(f.Name(), data, perm); err != nil {
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t.Fatal(err)
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}
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rData, err := ioutil.ReadFile(f.Name())
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if err != nil {
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t.Fatal(err)
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}
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if !bytes.Equal(data, rData) {
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t.Fatalf("data mismatch: %v != %v", data, rData)
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}
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if err := os.Remove(fname); err != nil {
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stat, err := os.Stat(f.Name())
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if err != nil {
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t.Fatal(err)
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}
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if have, want := stat.Mode().Perm(), perm; have != want {
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t.Errorf("have %v, want %v", have, want)
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}
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}
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func TestGoPath(t *testing.T) {
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