atomic/fs: use safe package for atomic writes, even in multipart.

pkg/safe/safe.go

@@ -0,0 +1,120 @@
+/*
+ * Minio Cloud Storage (C) 2015-2016 Minio, Inc.
+ *
+ * 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.
+ */
+
+// NOTE - Rename() not guaranteed to be safe on all filesystems which are not fully POSIX compatible
+
+// Package safe provides safe file write semantics by leveraging Rename's() safeity.
+package safe
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// File provides for safe file writes.
+type File struct {
+	*os.File
+	file string
+}
+
+// SyncClose sync file to disk and close, returns an error if any
+func (f *File) SyncClose() error {
+	// sync to the disk
+	if err := f.File.Sync(); err != nil {
+		return err
+	}
+	if err := f.Close(); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Close the file, returns an error if any
+func (f *File) Close() error {
+	// close the embedded fd
+	if err := f.File.Close(); err != nil {
+		return err
+	}
+	// safe rename to final destination
+	if err := os.Rename(f.Name(), f.file); err != nil {
+		return err
+	}
+	return nil
+}
+
+// CloseAndRemove closes the temp file, and safely removes it. Returns
+// error if any.
+func (f *File) CloseAndRemove() error {
+	// close the embedded fd
+	if err := f.File.Close(); err != nil {
+		return err
+	}
+	if err := os.Remove(f.Name()); err != nil {
+		return err
+	}
+	return nil
+}
+
+// CreateFile creates a new file at filePath for safe writes, it also
+// creates parent directories if they don't exist.
+func CreateFile(filePath string) (*File, error) {
+	return CreateFileWithPrefix(filePath, "$deleteme.")
+}
+
+// CreateFileWithSuffix is similar to CreateFileWithPrefix, but the
+// second argument is treated as suffix for the temporary files.
+func CreateFileWithSuffix(filePath string, suffix string) (*File, error) {
+	// If parent directories do not exist, ioutil.TempFile doesn't create them
+	// handle such a case with os.MkdirAll()
+	if err := os.MkdirAll(filepath.Dir(filePath), 0700); err != nil {
+		return nil, err
+	}
+	f, err := ioutil.TempFile(filepath.Dir(filePath), filepath.Base(filePath)+suffix)
+	if err != nil {
+		return nil, err
+	}
+	if err = os.Chmod(f.Name(), 0600); err != nil {
+		if err = os.Remove(f.Name()); err != nil {
+			return nil, err
+		}
+		return nil, err
+	}
+	return &File{File: f, file: filePath}, nil
+}
+
+// CreateFileWithPrefix creates a new file at filePath for safe
+// writes, it also creates parent directories if they don't exist.
+// prefix specifies the prefix of the temporary files so that cleaning
+// stale temp files is easy.
+func CreateFileWithPrefix(filePath string, prefix string) (*File, error) {
+	// If parent directories do not exist, ioutil.TempFile doesn't create them
+	// handle such a case with os.MkdirAll()
+	if err := os.MkdirAll(filepath.Dir(filePath), 0700); err != nil {
+		return nil, err
+	}
+	f, err := ioutil.TempFile(filepath.Dir(filePath), prefix+filepath.Base(filePath))
+	if err != nil {
+		return nil, err
+	}
+	if err = os.Chmod(f.Name(), 0600); err != nil {
+		if err = os.Remove(f.Name()); err != nil {
+			return nil, err
+		}
+		return nil, err
+	}
+	return &File{File: f, file: filePath}, nil
+}

pkg/safe/safe_test.go

@@ -0,0 +1,66 @@
+/*
+ * Minio Client (C) 2015 Minio, Inc.
+ *
+ * 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 safe
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type MySuite struct {
+	root string
+}
+
+var _ = Suite(&MySuite{})
+
+func (s *MySuite) SetUpSuite(c *C) {
+	root, err := ioutil.TempDir(os.TempDir(), "safe-")
+	c.Assert(err, IsNil)
+	s.root = root
+}
+
+func (s *MySuite) TearDownSuite(c *C) {
+	os.RemoveAll(s.root)
+}
+
+func (s *MySuite) TestSafe(c *C) {
+	f, err := CreateFile(filepath.Join(s.root, "testfile"))
+	c.Assert(err, IsNil)
+	_, err = os.Stat(filepath.Join(s.root, "testfile"))
+	c.Assert(err, Not(IsNil))
+	err = f.Close()
+	c.Assert(err, IsNil)
+	_, err = os.Stat(filepath.Join(s.root, "testfile"))
+	c.Assert(err, IsNil)
+}
+
+func (s *MySuite) TestSafePurge(c *C) {
+	f, err := CreateFile(filepath.Join(s.root, "purgefile"))
+	c.Assert(err, IsNil)
+	_, err = os.Stat(filepath.Join(s.root, "purgefile"))
+	c.Assert(err, Not(IsNil))
+	err = f.CloseAndRemove()
+	c.Assert(err, IsNil)
+	err = f.Close()
+	c.Assert(err, Not(IsNil))
+}