fix: cancel upload when BlobWriter exits with exception (#1243)

README.rst

@@ -72,6 +72,12 @@ setup.py file. Applications which do not import directly from
 `google-resumable-media` can safely disregard this dependency. This backwards
 compatibility feature will be removed in a future major version update.
 
+Miscellaneous
+~~~~~~~~~~~~~
+
+- The BlobWriter class now attempts to terminate an ongoing resumable upload if
+  the writer exits with an exception.
+
 Quick Start
 -----------
 

google/cloud/storage/fileio.py

@@ -437,6 +437,19 @@ def close(self):
             self._upload_chunks_from_buffer(1)
         self._buffer.close()
 
+    def terminate(self):
+        """Cancel the ResumableUpload."""
+        if self._upload_and_transport:
+            upload, transport = self._upload_and_transport
+            transport.delete(upload.upload_url)
+        self._buffer.close()
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if exc_type is not None:
+            self.terminate()
+        else:
+            self.close()
+
     @property
     def closed(self):
         return self._buffer.closed

tests/system/test_fileio.py

@@ -14,6 +14,9 @@
 # limitations under the License.
 
 
+import pytest
+
+from google.cloud.storage.fileio import CHUNK_SIZE_MULTIPLE
 from .test_blob import _check_blob_hash
 
 
@@ -76,3 +79,40 @@ def test_blobwriter_and_blobreader_text_mode(
         assert text_data[:100] == reader.read(100)
         assert 0 == reader.seek(0)
         assert reader.read() == text_data
+
+
+def test_blobwriter_exit(
+    shared_bucket,
+    blobs_to_delete,
+    service_account,
+):
+    blob = shared_bucket.blob("NeverUploaded")
+
+    # no-op when nothing was uploaded yet
+    with pytest.raises(ValueError, match="SIGTERM received"):
+        with blob.open("wb") as writer:
+            writer.write(b"first chunk")  # not yet uploaded
+            raise ValueError("SIGTERM received")  # no upload to cancel in __exit__
+    # blob should not exist
+    assert not blob.exists()
+
+    # unhandled exceptions should cancel the upload
+    with pytest.raises(ValueError, match="SIGTERM received"):
+        with blob.open("wb", chunk_size=CHUNK_SIZE_MULTIPLE) as writer:
+            writer.write(b"first chunk")  # not yet uploaded
+            writer.write(bytes(CHUNK_SIZE_MULTIPLE))  # uploaded
+            raise ValueError("SIGTERM received")  # upload is cancelled in __exit__
+    # blob should not exist
+    assert not blob.exists()
+
+    # handled exceptions should not cancel the upload
+    with blob.open("wb", chunk_size=CHUNK_SIZE_MULTIPLE) as writer:
+        writer.write(b"first chunk")  # not yet uploaded
+        writer.write(bytes(CHUNK_SIZE_MULTIPLE))  # uploaded
+        try:
+            raise ValueError("This is fine")
+        except ValueError:
+            pass  # no exception context passed to __exit__
+    blobs_to_delete.append(blob)
+    # blob should have been uploaded
+    assert blob.exists()

tests/unit/test_fileio.py

@@ -21,6 +21,7 @@
 import mock
 
 from google.api_core.exceptions import RequestRangeNotSatisfiable
+from google.cloud.storage.fileio import CHUNK_SIZE_MULTIPLE
 from google.cloud.storage.retry import DEFAULT_RETRY
 
 TEST_TEXT_DATA = string.ascii_lowercase + "\n" + string.ascii_uppercase + "\n"
@@ -377,7 +378,7 @@ def test_write(self, mock_warn):
         # Write under chunk_size. This should be buffered and the upload not
         # initiated.
         writer.write(TEST_BINARY_DATA[0:4])
-        blob.initiate_resumable_upload.assert_not_called()
+        blob._initiate_resumable_upload.assert_not_called()
 
         # Write over chunk_size. This should result in upload initialization
         # and multiple chunks uploaded.
@@ -426,6 +427,52 @@ def test_close_errors(self):
         with self.assertRaises(ValueError):
             writer.write(TEST_BINARY_DATA)
 
+    def test_terminate_after_initiate(self):
+        blob = mock.Mock()
+
+        upload = mock.Mock(upload_url="dummy")
+        transport = mock.Mock()
+
+        blob._initiate_resumable_upload.return_value = (upload, transport)
+
+        with self.assertRaises(RuntimeError):
+            with self._make_blob_writer(blob, chunk_size=CHUNK_SIZE_MULTIPLE) as writer:
+                writer.write(bytes(CHUNK_SIZE_MULTIPLE + 1))  # initiate upload
+                raise RuntimeError  # should terminate the upload
+        blob._initiate_resumable_upload.assert_called_once()  # upload initiated
+        self.assertTrue(writer.closed)  # terminate called
+        transport.delete.assert_called_with("dummy")  # resumable upload terminated
+
+    def test_terminate_before_initiate(self):
+        blob = mock.Mock()
+
+        upload = mock.Mock()
+        transport = mock.Mock()
+
+        blob._initiate_resumable_upload.return_value = (upload, transport)
+
+        with self.assertRaises(RuntimeError):
+            with self._make_blob_writer(blob, chunk_size=CHUNK_SIZE_MULTIPLE) as writer:
+                writer.write(bytes(CHUNK_SIZE_MULTIPLE - 1))  # upload not yet initiated
+                raise RuntimeError  # there is no resumable upload to terminate
+        blob._initiate_resumable_upload.assert_not_called()  # upload not yet initiated
+        self.assertTrue(writer.closed)  # terminate called
+        transport.delete.assert_not_called()  # there's no resumable upload to terminate
+
+    def test_terminate_skipped(self):
+        blob = mock.Mock()
+
+        upload = mock.Mock()
+        transport = mock.Mock()
+
+        blob._initiate_resumable_upload.return_value = (upload, transport)
+
+        with self._make_blob_writer(blob, chunk_size=CHUNK_SIZE_MULTIPLE) as writer:
+            writer.write(bytes(CHUNK_SIZE_MULTIPLE + 1))  # upload initiated
+        blob._initiate_resumable_upload.assert_called()  # upload initiated
+        self.assertTrue(writer.closed)  # close called
+        transport.delete.assert_not_called()  # terminate not called
+
     def test_flush_fails(self):
         blob = mock.Mock(chunk_size=None)
         writer = self._make_blob_writer(blob)
@@ -468,7 +515,7 @@ def test_conditional_retry_failure(self):
         # Write under chunk_size. This should be buffered and the upload not
         # initiated.
         writer.write(TEST_BINARY_DATA[0:4])
-        blob.initiate_resumable_upload.assert_not_called()
+        blob._initiate_resumable_upload.assert_not_called()
 
         # Write over chunk_size. This should result in upload initialization
         # and multiple chunks uploaded.
@@ -520,7 +567,7 @@ def test_conditional_retry_pass(self):
         # Write under chunk_size. This should be buffered and the upload not
         # initiated.
         writer.write(TEST_BINARY_DATA[0:4])
-        blob.initiate_resumable_upload.assert_not_called()
+        blob._initiate_resumable_upload.assert_not_called()
 
         # Write over chunk_size. This should result in upload initialization
         # and multiple chunks uploaded.
@@ -573,7 +620,7 @@ def test_forced_default_retry(self):
         # Write under chunk_size. This should be buffered and the upload not
         # initiated.
         writer.write(TEST_BINARY_DATA[0:4])
-        blob.initiate_resumable_upload.assert_not_called()
+        blob._initiate_resumable_upload.assert_not_called()
 
         # Write over chunk_size. This should result in upload initialization
         # and multiple chunks uploaded.
@@ -619,7 +666,7 @@ def test_num_retries_and_retry_conflict(self, mock_warn):
         # Write under chunk_size. This should be buffered and the upload not
         # initiated.
         writer.write(TEST_BINARY_DATA[0:4])
-        blob.initiate_resumable_upload.assert_not_called()
+        blob._initiate_resumable_upload.assert_not_called()
 
         # Write over chunk_size. The mock will raise a ValueError, simulating
         # actual behavior when num_retries and retry are both specified.
@@ -673,7 +720,7 @@ def test_num_retries_only(self, mock_warn):
         # Write under chunk_size. This should be buffered and the upload not
         # initiated.
         writer.write(TEST_BINARY_DATA[0:4])
-        blob.initiate_resumable_upload.assert_not_called()
+        blob._initiate_resumable_upload.assert_not_called()
 
         # Write over chunk_size. This should result in upload initialization
         # and multiple chunks uploaded.
@@ -965,7 +1012,7 @@ def test_write(self, mock_warn):
         # Write under chunk_size. This should be buffered and the upload not
         # initiated.
         writer.write(TEST_MULTIBYTE_TEXT_DATA[0:2])
-        blob.initiate_resumable_upload.assert_not_called()
+        blob._initiate_resumable_upload.assert_not_called()
 
         # Write all data and close.
         writer.write(TEST_MULTIBYTE_TEXT_DATA[2:])