Include symlinks in snapshots when migrating disks

client/allocdir/alloc_dir.go

@@ -118,26 +118,29 @@ func (d *AllocDir) Snapshot(w io.Writer) error {
 	defer tw.Close()
 
 	walkFn := func(path string, fileInfo os.FileInfo, err error) error {
-		// Ignore if the file is a symlink
-		if fileInfo.Mode() == os.ModeSymlink {
-			return nil
-		}
-
 		// Include the path of the file name relative to the alloc dir
 		// so that we can put the files in the right directories
 		relPath, err := filepath.Rel(d.AllocDir, path)
 		if err != nil {
 			return err
 		}
-		hdr, err := tar.FileInfoHeader(fileInfo, "")
+		link := ""
+		if fileInfo.Mode()&os.ModeSymlink != 0 {
+			target, err := os.Readlink(path)
+			if err != nil {
+				return fmt.Errorf("error reading symlink: %v", err)
+			}
+			link = target
+		}
+		hdr, err := tar.FileInfoHeader(fileInfo, link)
 		if err != nil {
 			return fmt.Errorf("error creating file header: %v", err)
 		}
 		hdr.Name = relPath
 		tw.WriteHeader(hdr)
 
-		// If it's a directory we just write the header into the tar
-		if fileInfo.IsDir() {
+		// If it's a directory or symlink we just write the header into the tar
+		if fileInfo.IsDir() || (fileInfo.Mode()&os.ModeSymlink != 0) {
 			return nil
 		}
 

client/allocdir/alloc_dir_test.go

@@ -166,11 +166,23 @@ func TestAllocDir_Snapshot(t *testing.T) {
 		t.Fatalf("Couldn't write file to shared directory: %v", err)
 	}
 
+	// Write a symlink to the shared dir
+	link := "qux"
+	if err := os.Symlink("foo", filepath.Join(d.SharedDir, "data", link)); err != nil {
+		t.Fatalf("Couldn't write symlink to shared directory: %v", err)
+	}
+
 	// Write a file to the task local
 	exp = []byte{'b', 'a', 'r'}
 	file1 := "lol"
 	if err := ioutil.WriteFile(filepath.Join(td1.LocalDir, file1), exp, 0666); err != nil {
-		t.Fatalf("couldn't write to task local directory: %v", err)
+		t.Fatalf("couldn't write file to task local directory: %v", err)
+	}
+
+	// Write a symlink to the task local
+	link1 := "baz"
+	if err := os.Symlink("bar", filepath.Join(td1.LocalDir, link1)); err != nil {
+		t.Fatalf("couldn't write symlink to task local dirctory :%v", err)
 	}
 
 	var b bytes.Buffer
@@ -180,6 +192,7 @@ func TestAllocDir_Snapshot(t *testing.T) {
 
 	tr := tar.NewReader(&b)
 	var files []string
+	var links []string
 	for {
 		hdr, err := tr.Next()
 		if err != nil && err != io.EOF {
@@ -190,12 +203,17 @@ func TestAllocDir_Snapshot(t *testing.T) {
 		}
 		if hdr.Typeflag == tar.TypeReg {
 			files = append(files, hdr.FileInfo().Name())
+		} else if hdr.Typeflag == tar.TypeSymlink {
+			links = append(links, hdr.FileInfo().Name())
 		}
 	}
 
 	if len(files) != 2 {
 		t.Fatalf("bad files: %#v", files)
 	}
+	if len(links) != 2 {
+		t.Fatalf("bad links: %#v", links)
+	}
 }
 
 func TestAllocDir_Move(t *testing.T) {

client/client.go

@@ -1851,6 +1851,13 @@ func (c *Client) unarchiveAllocDir(resp io.ReadCloser, allocID string, pathToAll
 			os.MkdirAll(filepath.Join(pathToAllocDir, hdr.Name), os.FileMode(hdr.Mode))
 			continue
 		}
+		// If the header is for a symlink we create the symlink
+		if hdr.Typeflag == tar.TypeSymlink {
+			if err = os.Symlink(hdr.Linkname, filepath.Join(pathToAllocDir, hdr.Name)); err != nil {
+				c.logger.Printf("[ERR] client: error creating symlink: %v", err)
+			}
+			continue
+		}
 		// If the header is a file, we write to a file
 		if hdr.Typeflag == tar.TypeReg {
 			f, err := os.Create(filepath.Join(pathToAllocDir, hdr.Name))

client/client_test.go

@@ -939,27 +939,37 @@ func TestClient_UnarchiveAllocDir(t *testing.T) {
 		t.Fatalf("err: %v", err)
 	}
 	f.Close()
+	if err := os.Symlink("bar", filepath.Join(dir, "foo", "baz")); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	linkInfo, err := os.Lstat(filepath.Join(dir, "foo", "baz"))
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
 
 	buf := new(bytes.Buffer)
 	tw := tar.NewWriter(buf)
 
 	walkFn := func(path string, fileInfo os.FileInfo, err error) error {
-		// Ignore if the file is a symlink
-		if fileInfo.Mode() == os.ModeSymlink {
-			return nil
-		}
-
 		// Include the path of the file name relative to the alloc dir
 		// so that we can put the files in the right directories
-		hdr, err := tar.FileInfoHeader(fileInfo, "")
+		link := ""
+		if fileInfo.Mode()&os.ModeSymlink != 0 {
+			target, err := os.Readlink(path)
+			if err != nil {
+				return fmt.Errorf("error reading symlink: %v", err)
+			}
+			link = target
+		}
+		hdr, err := tar.FileInfoHeader(fileInfo, link)
 		if err != nil {
 			return fmt.Errorf("error creating file header: %v", err)
 		}
 		hdr.Name = fileInfo.Name()
 		tw.WriteHeader(hdr)
 
-		// If it's a directory we just write the header into the tar
-		if fileInfo.IsDir() {
+		// If it's a directory or symlink we just write the header into the tar
+		if fileInfo.IsDir() || (fileInfo.Mode()&os.ModeSymlink != 0) {
 			return nil
 		}
 
@@ -1016,4 +1026,12 @@ func TestClient_UnarchiveAllocDir(t *testing.T) {
 	if fi1.Mode() != fInfo.Mode() {
 		t.Fatalf("mode: %v", fi1.Mode())
 	}
+
+	fi2, err := os.Lstat(filepath.Join(dir1, "baz"))
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if fi2.Mode() != linkInfo.Mode() {
+		t.Fatalf("mode: %v", fi2.Mode())
+	}
 }