Add support for extended filesystem attributes ("XAttrs")

Author: colinmarc

error.go

@@ -9,7 +9,7 @@ const (
 	fileNotFoundException      = "java.io.FileNotFoundException"
 	permissionDeniedException  = "org.apache.hadoop.security.AccessControlException"
 	pathIsNotEmptyDirException = "org.apache.hadoop.fs.PathIsNotEmptyDirectoryException"
-	FileAlreadyExistsException = "org.apache.hadoop.fs.FileAlreadyExistsException"
+	fileAlreadyExistsException = "org.apache.hadoop.fs.fileAlreadyExistsException"
 )
 
 // Error represents a remote java exception from an HDFS namenode or datanode.
@@ -39,7 +39,7 @@ func interpretException(err error) error {
 		return os.ErrPermission
 	case pathIsNotEmptyDirException:
 		return syscall.ENOTEMPTY
-	case FileAlreadyExistsException:
+	case fileAlreadyExistsException:
 		return os.ErrExist
 	default:
 		return err

xattr.go

@@ -0,0 +1,171 @@
+package hdfs
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+
+	hdfs "github.com/colinmarc/hdfs/v2/internal/protocol/hadoop_hdfs"
+	"github.com/golang/protobuf/proto"
+)
+
+var errXAttrKeysNotFound = errors.New("one or more keys not found")
+
+const createAndReplace = 3
+
+// ListXAttrs returns a list of all extended attributes for the given path.
+// The returned keys will be in the form
+func (c *Client) ListXAttrs(name string) (map[string]string, error) {
+	req := &hdfs.ListXAttrsRequestProto{Src: proto.String(name)}
+	resp := &hdfs.ListXAttrsResponseProto{}
+
+	err := c.namenode.Execute("listXAttrs", req, resp)
+	if err != nil {
+		return nil, &os.PathError{"list xattrs", name, interpretException(err)}
+	}
+
+	return xattrMap(resp.GetXAttrs()), nil
+}
+
+// GetXAttrs returns the extended attributes for the given path and list of
+// keys. The keys should be prefixed by namespace, e.g. user.foo or trusted.bar.
+func (c *Client) GetXAttrs(name string, keys ...string) (map[string]string, error) {
+	if len(keys) == 0 {
+		return make(map[string]string), nil
+	}
+
+	req := &hdfs.GetXAttrsRequestProto{Src: proto.String(name)}
+	for _, key := range keys {
+		ns, rest, err := splitKey(key)
+		if err != nil {
+			return nil, &os.PathError{"get xattrs", name, err}
+		}
+
+		req.XAttrs = append(req.XAttrs, &hdfs.XAttrProto{
+			Namespace: ns,
+			Name:      proto.String(rest),
+		})
+	}
+	resp := &hdfs.GetXAttrsResponseProto{}
+
+	err := c.namenode.Execute("getXAttrs", req, resp)
+	if err != nil {
+		if isKeyNotFound(err) {
+			return nil, &os.PathError{"get xattrs", name, errXAttrKeysNotFound}
+		}
+
+		return nil, &os.PathError{"get xattrs", name, interpretException(err)}
+	}
+
+	return xattrMap(resp.GetXAttrs()), nil
+}
+
+// SetXAttr sets an extended attribute for the given path and key. If the
+// attribute doesn't exist, it will be created.
+func (c *Client) SetXAttr(name, key, value string) error {
+	resp := &hdfs.SetXAttrResponseProto{}
+
+	ns, rest, err := splitKey(key)
+	if err != nil {
+		return &os.PathError{"set xattr", name, err}
+	}
+
+	req := &hdfs.SetXAttrRequestProto{
+		Src: proto.String(name),
+		XAttr: &hdfs.XAttrProto{
+			Namespace: ns.Enum(),
+			Name:      proto.String(rest),
+			Value:     []byte(value),
+		},
+		Flag: proto.Uint32(createAndReplace),
+	}
+
+	err = c.namenode.Execute("setXAttr", req, resp)
+	if err != nil {
+		return &os.PathError{"set xattr", name, interpretException(err)}
+	}
+
+	return nil
+}
+
+// RemoveXAttr unsets an extended attribute for the given path and key. It
+// returns an error if the attribute doesn't already exist.
+func (c *Client) RemoveXAttr(name, key string) error {
+	ns, rest, err := splitKey(key)
+	if err != nil {
+		return &os.PathError{"remove xattr", name, err}
+	}
+
+	req := &hdfs.RemoveXAttrRequestProto{
+		Src: proto.String(name),
+		XAttr: &hdfs.XAttrProto{
+			Namespace: ns,
+			Name:      proto.String(rest),
+		},
+	}
+	resp := &hdfs.RemoveXAttrResponseProto{}
+
+	err = c.namenode.Execute("removeXAttr", req, resp)
+	if err != nil {
+		if isKeyNotFound(err) {
+			return &os.PathError{"remove xattr", name, errXAttrKeysNotFound}
+		}
+
+		return &os.PathError{"remove xattr", name, interpretException(err)}
+	}
+
+	return nil
+}
+
+func splitKey(key string) (*hdfs.XAttrProto_XAttrNamespaceProto, string, error) {
+	parts := strings.SplitN(key, ".", 2)
+	if len(parts) < 2 {
+		return nil, "", fmt.Errorf("invalid key: '%s'", key)
+	}
+
+	var ns hdfs.XAttrProto_XAttrNamespaceProto
+	switch strings.ToLower(parts[0]) {
+	case "user":
+		ns = hdfs.XAttrProto_USER
+	case "trusted":
+		ns = hdfs.XAttrProto_TRUSTED
+	case "system":
+		ns = hdfs.XAttrProto_SYSTEM
+	case "security":
+		ns = hdfs.XAttrProto_SECURITY
+	case "raw":
+		ns = hdfs.XAttrProto_RAW
+	default:
+		return nil, "", fmt.Errorf("invalid key namespace: '%s'", parts[0])
+	}
+
+	return ns.Enum(), parts[1], nil
+}
+
+func xattrMap(attrs []*hdfs.XAttrProto) map[string]string {
+	m := make(map[string]string)
+	for _, xattr := range attrs {
+		key := fmt.Sprintf("%s.%s",
+			strings.ToLower(xattr.GetNamespace().String()), xattr.GetName())
+		m[key] = string(xattr.GetValue())
+	}
+
+	return m
+}
+
+func isKeyNotFound(err error) bool {
+	if remoteErr, ok := err.(Error); ok {
+		if strings.HasPrefix(remoteErr.Message(),
+			"At least one of the attributes provided was not found") {
+			return true
+		}
+
+		if strings.HasPrefix(remoteErr.Message(),
+			"No matching attributes found for remove operation") {
+			return true
+		}
+	}
+
+	return false
+}