[AIR] Checkpoint improvements

python/ray/air/checkpoint.py

@@ -156,7 +156,7 @@ class Checkpoint:
     @DeveloperAPI
     def __init__(
         self,
-        local_path: Optional[str] = None,
+        local_path: Optional[Union[str, os.PathLike]] = None,
         data_dict: Optional[dict] = None,
         uri: Optional[str] = None,
         obj_ref: Optional[ray.ObjectRef] = None,
@@ -210,7 +210,9 @@ def __init__(
         else:
             raise ValueError("Cannot create checkpoint without data.")
 
-        self._local_path: Optional[str] = local_path
+        self._local_path: Optional[str] = (
+            str(Path(local_path).resolve()) if local_path else local_path
+        )
         self._data_dict: Optional[Dict[str, Any]] = data_dict
         self._uri: Optional[str] = uri
         self._obj_ref: Optional[ray.ObjectRef] = obj_ref
@@ -230,6 +232,22 @@ def _metadata(self) -> _CheckpointMetadata:
             },
         )
 
+    def _copy_metadata_attrs_from(self, source: "Checkpoint") -> None:
+        """Copy in-place metadata attributes from ``source`` to self."""
+        for attr, value in source._metadata.checkpoint_state.items():
+            if attr in self._SERIALIZED_ATTRS:
+                setattr(self, attr, value)
+
+    @_metadata.setter
+    def _metadata(self, metadata: _CheckpointMetadata):
+        if metadata.checkpoint_type is not self.__class__:
+            raise ValueError(
+                f"Checkpoint type in metadata must match {self.__class__}, "
+                f"got {metadata.checkpoint_type}"
+            )
+        for attr, value in metadata.checkpoint_state.items():
+            setattr(self, attr, value)
+
     @property
     def uri(self) -> Optional[str]:
         """Return checkpoint URI, if available.
@@ -259,7 +277,7 @@ def uri(self) -> Optional[str]:
             return self._uri
 
         if self._local_path and Path(self._local_path).exists():
-            return "file://" + self._local_path
+            return f"file://{self._local_path}"
 
         return None
 
@@ -290,7 +308,7 @@ def to_bytes(self) -> bytes:
         data_dict = self.to_dict()
         if "bytes_data" in data_dict:
             return data_dict["bytes_data"]
-        return pickle.dumps(self.to_dict())
+        return pickle.dumps(data_dict)
 
     @classmethod
     def from_dict(cls, data: dict) -> "Checkpoint":
@@ -421,7 +439,7 @@ def to_object_ref(self) -> ray.ObjectRef:
         )
 
     @classmethod
-    def from_directory(cls, path: str) -> "Checkpoint":
+    def from_directory(cls, path: Union[str, os.PathLike]) -> "Checkpoint":
         """Create checkpoint object from directory.
 
         Args:
@@ -463,12 +481,14 @@ def from_checkpoint(cls, other: "Checkpoint") -> "Checkpoint":
         if type(other) is cls:
             return other
 
-        return cls(
+        new_checkpoint = cls(
             local_path=other._local_path,
             data_dict=other._data_dict,
             uri=other._uri,
             obj_ref=other._obj_ref,
         )
+        new_checkpoint._copy_metadata_attrs_from(other)
+        return new_checkpoint
 
     def _get_temporary_checkpoint_dir(self) -> str:
         """Return the name for the temporary checkpoint dir."""
@@ -532,7 +552,7 @@ def _to_directory(self, path: str) -> None:
             local_path = self._local_path
             external_path = _get_external_path(self._uri)
             if local_path:
-                if local_path != path:
+                if Path(local_path).resolve() != Path(path).resolve():
                     # If this exists on the local path, just copy over
                     if path and os.path.exists(path):
                         shutil.rmtree(path)

python/ray/air/tests/test_checkpoints.py

@@ -4,6 +4,7 @@
 import shutil
 import tempfile
 import unittest
+from pathlib import Path
 from typing import Any
 
 import pytest
@@ -47,6 +48,10 @@ class OtherStubCheckpoint(Checkpoint):
     pass
 
 
+class OtherStubCheckpointWithAttrs(Checkpoint):
+    _SERIALIZED_ATTRS = StubCheckpoint._SERIALIZED_ATTRS
+
+
 def test_from_checkpoint():
     checkpoint = Checkpoint.from_dict({"spam": "ham"})
     assert type(StubCheckpoint.from_checkpoint(checkpoint)) is StubCheckpoint
@@ -56,6 +61,13 @@ def test_from_checkpoint():
     checkpoint.foo = "bar"
     assert StubCheckpoint.from_checkpoint(checkpoint).foo == "bar"
 
+    # Check that attributes persist if the new checkpoint
+    # has them as well.
+    # Check that attributes persist if same checkpoint type.
+    checkpoint = StubCheckpoint.from_dict({"spam": "ham"})
+    checkpoint.foo = "bar"
+    assert OtherStubCheckpointWithAttrs.from_checkpoint(checkpoint).foo == "bar"
+
 
 class TestCheckpointTypeCasting:
     def test_dict(self):
@@ -491,7 +503,7 @@ def test_obj_store_cp_as_directory(self):
 
         with checkpoint.as_directory() as checkpoint_dir:
             assert os.path.exists(checkpoint_dir)
-            assert checkpoint_dir.endswith(checkpoint._uuid.hex)
+            assert Path(checkpoint_dir).stem.endswith(checkpoint._uuid.hex)
 
         assert not os.path.exists(checkpoint_dir)
 

python/ray/tune/tests/test_trainable_util.py

@@ -5,6 +5,7 @@
 import sys
 import shutil
 import unittest
+from pathlib import Path
 from unittest.mock import patch
 
 import ray
@@ -61,7 +62,7 @@ def tune_one(config=None, checkpoint_dir=None):
         )
         df = a.dataframe()
         checkpoint_dir = a.get_best_checkpoint(df["logdir"].iloc[0])._local_path
-        assert checkpoint_dir.endswith("/checkpoint_000001/")
+        assert Path(checkpoint_dir).stem == "checkpoint_000001"
 
     def testFindCheckpointDir(self):
         checkpoint_path = os.path.join(self.checkpoint_dir, "0/my/nested/chkpt")