Do not leave 0-byte multipart files in Cloud Storage

storage/cloud.py

@@ -396,6 +396,13 @@ def initiate_chunked_upload(self):
     def stream_upload_chunk(self, uuid, offset, length, in_fp, storage_metadata, content_type=None):
         self._initialize_cloud_conn()
 
+        # Do not create zero-byte objects.
+        # TODO: length=-1 appears to be a special case and used in tests. Why? Document it.
+        if length == 0:
+            logger.debug("Attempted to upload a zero-byte chunk to cloud storage. Ignoring.")
+            new_metadata = copy.deepcopy(storage_metadata)
+            return 0, new_metadata, None
+
         # We are going to upload each chunk to a separate key
         chunk_path = self._rel_upload_path(str(uuid4()))
         bytes_written, write_error = self._stream_write_internal(
@@ -408,6 +415,12 @@ def stream_upload_chunk(self, uuid, offset, length, in_fp, storage_metadata, con
         if bytes_written > 0:
             new_metadata[_CHUNKS_KEY].append(_PartUploadMetadata(chunk_path, offset, bytes_written))
 
+        # Do not leave zero-byte chunks in Object Storage
+        # TODO: Determine a clean way to eliminate calling this function when it's not needed.
+        else:
+            logger.debug("Wrote zero bytes to Object Storage. Removing orphaned object.")
+            self.remove(chunk_path)
+
         return bytes_written, new_metadata, write_error
 
     def _chunk_generator(self, chunk_list):

storage/test/test_cloud_storage.py

@@ -1,6 +1,7 @@
 import os
 
 from io import BytesIO
+from mock import patch
 
 import pytest
 
@@ -275,3 +276,19 @@ def test_rechunked(max_size, parts):
     assert len(rechunked) == len(parts)
     for index, chunk in enumerate(rechunked):
         assert chunk == parts[index]
+
+
+def test_no_orphaned_multipart_objects(storage_engine):
+    """
+    Ensure Quay is not creating orphaned multi-part objects in Cloud Storage.
+    """
+    with patch.object(storage_engine, "remove") as mock_remove:
+
+        upload_id, metadata = storage_engine.initiate_chunked_upload()
+        data = b""
+        bytes_written, new_metadata, errors = storage_engine.stream_upload_chunk(
+            upload_id, 0, -1, BytesIO(data), metadata
+        )
+        assert len(data) == bytes_written
+        assert mock_remove.call_count == 1
+        assert errors == None