googleapis · chandra-siri · Dec 16, 2025 · Dec 3, 2025 · Dec 5, 2025 · Dec 8, 2025
@@ -114,7 +114,11 @@ def __init__(
             write_handle=self.write_handle,
         )
         self._is_stream_open: bool = False
+        # `offset` is the latest size of the object without staleless.
         self.offset: Optional[int] = None
+        # `persisted_size` is the total_bytes persisted in the GCS server.
+        # Please note: `offset` and `persisted_size` are same when the stream is
+        # opened.
         self.persisted_size: Optional[int] = None
 
     async def state_lookup(self) -> int:
@@ -152,17 +156,17 @@ async def open(self) -> None:
         if self.generation is None:
             self.generation = self.write_obj_stream.generation_number
         self.write_handle = self.write_obj_stream.write_handle
-
-        # Update self.persisted_size
-        _ = await self.state_lookup()
+        self.persisted_size = self.write_obj_stream.persisted_size
 
     async def append(self, data: bytes) -> None:
         """Appends data to the Appendable object.
 
-        This method sends the provided data to the GCS server in chunks. It
-        maintains an internal threshold `_MAX_BUFFER_SIZE_BYTES` and will
-        automatically flush the data to make it visible to readers when that
-        threshold has reached.
+        calling `self.append` will append bytes at the end of the current size
+        ie. `self.offset` bytes relative to the begining of the object.
+
+        This method sends the provided `data` to the GCS server in chunks.
+        and persists data in GCS at every `_MAX_BUFFER_SIZE_BYTES` bytes by
+        calling `self.simple_flush`.
 
         :type data: bytes
         :param data: The bytes to append to the object.

@@ -216,7 +216,8 @@ async def download_ranges(
 
         :type read_ranges: List[Tuple[int, int, "BytesIO"]]
         :param read_ranges: A list of tuples, where each tuple represents a
-            byte range (start_byte, bytes_to_read, writeable_buffer). Buffer has
+            combintaion of byte_range and writeable buffer in format -
+            (`start_byte`, `bytes_to_read`, `writeable_buffer`). Buffer has
             to be provided by the user, and user has to make sure appropriate
             memory is available in the application to avoid out-of-memory crash.
 

@@ -117,7 +117,6 @@ async def open(self) -> None:
                     object=self.object_name,
                     generation=self.generation_number,
                 ),
-                state_lookup=True,
             )
 
         self.socket_like_rpc = AsyncBidiRpc(
@@ -136,11 +135,17 @@ async def open(self) -> None:
             raise ValueError(
                 "Failed to obtain object generation after opening the stream"
             )
-        self.generation_number = response.resource.generation
 
         if not response.write_handle:
             raise ValueError("Failed to obtain write_handle after opening the stream")
 
+        if not response.resource.size:
+            # Appending to a 0 byte appendable object.
+            self.persisted_size = 0
+        else:
+            self.persisted_size = response.resource.size
+
+        self.generation_number = response.resource.generation
         self.write_handle = response.write_handle
 
     async def close(self) -> None:

@@ -133,15 +133,10 @@ async def test_open_appendable_object_writer(mock_write_object_stream, mock_clie
     writer = AsyncAppendableObjectWriter(mock_client, BUCKET, OBJECT)
     mock_stream = mock_write_object_stream.return_value
     mock_stream.open = mock.AsyncMock()
-    mock_stream.send = mock.AsyncMock()
-    mock_stream.recv = mock.AsyncMock()
-
-    mock_state_response = mock.MagicMock()
-    mock_state_response.persisted_size = 1024
-    mock_stream.recv.return_value = mock_state_response
 
     mock_stream.generation_number = GENERATION
     mock_stream.write_handle = WRITE_HANDLE
+    mock_stream.persisted_size = 0
 
     # Act
     await writer.open()
@@ -151,11 +146,37 @@ async def test_open_appendable_object_writer(mock_write_object_stream, mock_clie
     assert writer._is_stream_open
     assert writer.generation == GENERATION
     assert writer.write_handle == WRITE_HANDLE
+    assert writer.persisted_size == 0
 
-    expected_request = _storage_v2.BidiWriteObjectRequest(state_lookup=True)
-    mock_stream.send.assert_awaited_once_with(expected_request)
-    mock_stream.recv.assert_awaited_once()
-    assert writer.persisted_size == 1024
+
+@pytest.mark.asyncio
+@mock.patch(
+    "google.cloud.storage._experimental.asyncio.async_appendable_object_writer._AsyncWriteObjectStream"
+)
+async def test_open_appendable_object_writer_existing_object(
+    mock_write_object_stream, mock_client
+):
+    """Test the open method."""
+    # Arrange
+    writer = AsyncAppendableObjectWriter(
+        mock_client, BUCKET, OBJECT, generation=GENERATION
+    )
+    mock_stream = mock_write_object_stream.return_value
+    mock_stream.open = mock.AsyncMock()
+
+    mock_stream.generation_number = GENERATION
+    mock_stream.write_handle = WRITE_HANDLE
+    mock_stream.persisted_size = PERSISTED_SIZE
+
+    # Act
+    await writer.open()
+
+    # Assert
+    mock_stream.open.assert_awaited_once()
+    assert writer._is_stream_open
+    assert writer.generation == GENERATION
+    assert writer.write_handle == WRITE_HANDLE
+    assert writer.persisted_size == PERSISTED_SIZE
 
 
 @pytest.mark.asyncio

@@ -55,6 +55,7 @@ async def instantiate_write_obj_stream(mock_client, mock_cls_async_bidi_rpc, ope
     mock_response = mock.MagicMock(spec=_storage_v2.BidiWriteObjectResponse)
     mock_response.resource = mock.MagicMock(spec=_storage_v2.Object)
     mock_response.resource.generation = GENERATION
+    mock_response.resource.size = 0
     mock_response.write_handle = WRITE_HANDLE
     socket_like_rpc.recv = AsyncMock(return_value=mock_response)
 
@@ -129,6 +130,7 @@ async def test_open_for_new_object(mock_async_bidi_rpc, mock_client):
     mock_response = mock.MagicMock(spec=_storage_v2.BidiWriteObjectResponse)
     mock_response.resource = mock.MagicMock(spec=_storage_v2.Object)
     mock_response.resource.generation = GENERATION
+    mock_response.resource.size = 0
     mock_response.write_handle = WRITE_HANDLE
     socket_like_rpc.recv = mock.AsyncMock(return_value=mock_response)
 
@@ -143,6 +145,7 @@ async def test_open_for_new_object(mock_async_bidi_rpc, mock_client):
     socket_like_rpc.recv.assert_called_once()
     assert stream.generation_number == GENERATION
     assert stream.write_handle == WRITE_HANDLE
+    assert stream.persisted_size == 0
 
 
 @pytest.mark.asyncio
@@ -158,6 +161,7 @@ async def test_open_for_existing_object(mock_async_bidi_rpc, mock_client):
 
     mock_response = mock.MagicMock(spec=_storage_v2.BidiWriteObjectResponse)
     mock_response.resource = mock.MagicMock(spec=_storage_v2.Object)
+    mock_response.resource.size = 1024
     mock_response.resource.generation = GENERATION
     mock_response.write_handle = WRITE_HANDLE
     socket_like_rpc.recv = mock.AsyncMock(return_value=mock_response)
@@ -175,6 +179,7 @@ async def test_open_for_existing_object(mock_async_bidi_rpc, mock_client):
     socket_like_rpc.recv.assert_called_once()
     assert stream.generation_number == GENERATION
     assert stream.write_handle == WRITE_HANDLE
+    assert stream.persisted_size == 1024
 
 
 @pytest.mark.asyncio
@@ -191,6 +196,7 @@ async def test_open_when_already_open_raises_error(mock_async_bidi_rpc, mock_cli
     mock_response = mock.MagicMock(spec=_storage_v2.BidiWriteObjectResponse)
     mock_response.resource = mock.MagicMock(spec=_storage_v2.Object)
     mock_response.resource.generation = GENERATION
+    mock_response.resource.size = 0
     mock_response.write_handle = WRITE_HANDLE
     socket_like_rpc.recv = mock.AsyncMock(return_value=mock_response)