Fix stream_write to properly raise an exception on failure, instead of just silently failing

This was causing problems for customers using georeplication over unstable storage engines

Also adds tests for stream_write and copy,  to ensure we detect failure

storage/basestorage.py

@@ -84,7 +84,7 @@ class BaseStorage(StoragePaths):
 
   def stream_write_to_fp(self, in_fp, out_fp, num_bytes=READ_UNTIL_END):
     """ Copy the specified number of bytes from the input file stream to the output stream. If
-        num_bytes < 0 copy until the stream ends.
+        num_bytes < 0 copy until the stream ends. Returns the number of bytes copied.
     """
     bytes_copied = 0
     while bytes_copied < num_bytes or num_bytes == READ_UNTIL_END:

storage/cloud.py

@@ -182,12 +182,28 @@ class _CloudStorage(BaseStorageV2):
                                                         **self._upload_params)
 
   def stream_write(self, path, fp, content_type=None, content_encoding=None):
-    self._stream_write_internal(path, fp, content_type, content_encoding)
+    """ Writes the data found in the file-like stream tot he given path. Raises an IOError
+        if the write fails.
+    """
+    _, write_error = self._stream_write_internal(path, fp, content_type, content_encoding)
+    if write_error is not None:
+      logger.error('Error when trying to stream_write path `%s`: %s', path, write_error)
+      raise IOError('Exception when trying to stream_write path')
 
   def _stream_write_internal(self, path, fp, content_type=None, content_encoding=None,
                              cancel_on_error=True, size=filelike.READ_UNTIL_END):
+    """ Writes the data found in the file-like stream to the given path, with optional limit
+        on size. Note that this method returns a *tuple* of (bytes_written, write_error) and should
+        *not* raise an exception (such as IOError) if a problem uploading occurred. ALWAYS check
+        the returned tuple on calls to this method.
+    """
     write_error = None
+
+    try:
       mp = self.__initiate_multipart_upload(path, content_type, content_encoding)
+    except S3ResponseError as e:
+      logger.exception('Exception when initiating multipart upload')
+      return 0, e
 
     # We are going to reuse this but be VERY careful to only read the number of bytes written to it
     buf = StringIO.StringIO()
@@ -211,7 +227,7 @@ class _CloudStorage(BaseStorageV2):
         mp.upload_part_from_file(buf, num_part, size=bytes_staged)
         total_bytes_written += bytes_staged
         num_part += 1
-      except IOError as e:
+      except (S3ResponseError, IOError) as e:
         logger.warn('Error when writing to stream in stream_write_internal at path %s: %s', path, e)
         write_error = e
 
@@ -219,7 +235,11 @@ class _CloudStorage(BaseStorageV2):
           self._context.metric_queue.multipart_upload_end.Inc(labelvalues=['failure'])
 
         if cancel_on_error:
+          try:
             mp.cancel_upload()
+          except (S3ResponseError, IOError):
+            logger.exception('Could not cancel upload')
+
           return 0, write_error
         else:
           break
@@ -263,6 +283,7 @@ class _CloudStorage(BaseStorageV2):
     return k.etag[1:-1][:7]
 
   def copy_to(self, destination, path):
+    """ Copies the given path from this storage to the destination storage. """
     self._initialize_cloud_conn()
 
     # First try to copy directly via boto, but only if the storages are the
@@ -527,6 +548,11 @@ class GoogleCloudStorage(_CloudStorage):
 
   def _stream_write_internal(self, path, fp, content_type=None, content_encoding=None,
                              cancel_on_error=True, size=filelike.READ_UNTIL_END):
+    """ Writes the data found in the file-like stream to the given path, with optional limit
+        on size. Note that this method returns a *tuple* of (bytes_written, write_error) and should
+        *not* raise an exception (such as IOError) if a problem uploading occurred. ALWAYS check
+        the returned tuple on calls to this method.
+    """
     # Minimum size of upload part size on S3 is 5MB
     self._initialize_cloud_conn()
     path = self._init_path(path)

storage/test/test_cloud_storage.py

@@ -7,6 +7,8 @@ import pytest
 import moto
 import boto
 
+from moto import mock_s3
+
 from storage import S3Storage, StorageContext
 from storage.cloud import _CloudStorage, _PartUploadMetadata
 from storage.cloud import _CHUNKS_KEY
@@ -56,28 +58,29 @@ def test_basicop(storage_engine):
   assert not storage_engine.exists(_TEST_PATH)
 
 
-def test_copy_samecreds(storage_engine):
+@pytest.mark.parametrize('bucket, username, password', [
+  pytest.param(_TEST_BUCKET, _TEST_USER, _TEST_PASSWORD, id='same credentials'),
+  pytest.param('another_bucket', 'blech', 'password', id='different credentials'),
+])
+def test_copy(bucket, username, password, storage_engine):
   # Copy the content to another engine.
   another_engine = S3Storage(_TEST_CONTEXT, 'another/path', _TEST_BUCKET, _TEST_USER,
                              _TEST_PASSWORD)
-  storage_engine.copy_to(another_engine, _TEST_PATH)
-
-  # Verify it can be retrieved.
-  assert another_engine.get_content(_TEST_PATH) == _TEST_CONTENT
-
-
-def test_copy_differentcreds(storage_engine):
-  # Copy the content to another engine.
-  another_engine = S3Storage(_TEST_CONTEXT, 'another/path', 'another_bucket', 'blech',
-                             'password')
   boto.connect_s3().create_bucket('another_bucket')
-
   storage_engine.copy_to(another_engine, _TEST_PATH)
 
   # Verify it can be retrieved.
   assert another_engine.get_content(_TEST_PATH) == _TEST_CONTENT
 
 
+def test_copy_with_error(storage_engine):
+  another_engine = S3Storage(_TEST_CONTEXT, 'another/path', 'anotherbucket', 'foo',
+                             'bar')
+
+  with pytest.raises(IOError):
+    storage_engine.copy_to(another_engine, _TEST_PATH)
+
+
 def test_stream_read(storage_engine):
   # Read the streaming content.
   data = ''.join(storage_engine.stream_read(_TEST_PATH))
@@ -95,6 +98,18 @@ def test_stream_write(storage_engine):
   assert storage_engine.get_content(_TEST_PATH) == new_data
 
 
+def test_stream_write_error():
+  with mock_s3():
+    # Create an engine but not the bucket.
+    engine = S3Storage(_TEST_CONTEXT, 'some/path', _TEST_BUCKET, _TEST_USER, _TEST_PASSWORD)
+
+    # Attempt to write to the uncreated bucket, which should raise an error.
+    with pytest.raises(IOError):
+      engine.stream_write(_TEST_PATH, StringIO('hello world'), content_type='Cool/Type')
+
+    assert not engine.exists(_TEST_PATH)
+
+
 @pytest.mark.parametrize('chunk_count', [
   0,
   1,