[sftp] Improve write & memory performance when saving files (#1194)

* Move seekability test to a separate helper function

Having a third copy of this code would feel silly.

* Stop calling content.open() from SFTPStorage._save

The open method isn't available in all file-like objects one might want to
save using the storage framework, so instead of relying on it calling
seek(0) for us do it ourselves (conditionally).

* Require at least version 1.10.0 of paramiko

This version introduced the SFTPClient.putfo() method. It was released in
early 2013, so this shouldn't be a great hardship.

* Use SFTPClient.putfo() in SFTPStorage._save()

Instead of using SFTPClient.open() to get a file-like object, reading the
entire content into memory and then calling .write() on that.

The measured performance difference is stunning, and the uploaded file data
no longer needs to fit into memory.

setup.cfg

@@ -46,7 +46,7 @@ google =
 libcloud =
     apache-libcloud
 sftp =
-    paramiko
+    paramiko >= 1.10.0
 
 [flake8]
 exclude =

storages/backends/gcloud.py

@@ -15,6 +15,7 @@
 from storages.utils import check_location
 from storages.utils import clean_name
 from storages.utils import get_available_overwrite_name
+from storages.utils import is_seekable
 from storages.utils import safe_join
 from storages.utils import setting
 from storages.utils import to_bytes
@@ -194,7 +195,7 @@ def _save(self, name, content):
         for prop, val in blob_params.items():
             setattr(file_object.blob, prop, val)
 
-        rewind = not hasattr(content, 'seekable') or content.seekable()
+        rewind = is_seekable(content)
         file_object.blob.upload_from_file(
             content,
             rewind=rewind,

storages/backends/s3boto3.py

@@ -24,6 +24,7 @@
 from storages.compress import CompressStorageMixin
 from storages.utils import check_location
 from storages.utils import get_available_overwrite_name
+from storages.utils import is_seekable
 from storages.utils import lookup_env
 from storages.utils import safe_join
 from storages.utils import setting
@@ -445,7 +446,7 @@ def _save(self, name, content):
         name = self._normalize_name(cleaned_name)
         params = self._get_write_parameters(name, content)
 
-        if not hasattr(content, 'seekable') or content.seekable():
+        if is_seekable(content):
             content.seek(0, os.SEEK_SET)
         if (self.gzip and
                 params['ContentType'] in self.gzip_content_types and

storages/backends/sftpstorage.py

@@ -17,6 +17,7 @@
 from django.utils.deconstruct import deconstructible
 
 from storages.base import BaseStorage
+from storages.utils import is_seekable
 from storages.utils import setting
 
 
@@ -123,15 +124,14 @@ def _mkdir(self, path):
 
     def _save(self, name, content):
         """Save file via SFTP."""
-        content.open()
+        if is_seekable(content):
+            content.seek(0, os.SEEK_SET)
         path = self._remote_path(name)
         dirname = posixpath.dirname(path)
         if not self.exists(dirname):
             self._mkdir(dirname)
 
-        f = self.sftp.open(path, 'wb')
-        f.write(content.file.read())
-        f.close()
+        self.sftp.putfo(content, path)
 
         # set file permissions if configured
         if self._file_mode is not None:

storages/utils.py

@@ -125,3 +125,7 @@ def get_available_overwrite_name(name, max_length):
             'allows sufficient "max_length".' % name
         )
     return os.path.join(dir_name, "{}{}".format(file_root, file_ext))
+
+
+def is_seekable(file_object):
+    return not hasattr(file_object, 'seekable') or file_object.seekable()

tests/test_sftp.py

@@ -12,6 +12,7 @@
 from django.test import override_settings
 
 from storages.backends import sftpstorage
+from tests.utils import NonSeekableContentFile
 
 
 class SFTPStorageTest(TestCase):
@@ -69,15 +70,20 @@ def test_mkdir_parent(self, mock_sftp):
     @patch('storages.backends.sftpstorage.SFTPStorage.sftp')
     def test_save(self, mock_sftp):
         self.storage._save('foo', File(io.BytesIO(b'foo'), 'foo'))
-        self.assertTrue(mock_sftp.open.return_value.write.called)
+        self.assertTrue(mock_sftp.putfo.called)
+
+    @patch('storages.backends.sftpstorage.SFTPStorage.sftp')
+    def test_save_non_seekable(self, mock_sftp):
+        self.storage._save('foo', NonSeekableContentFile('foo'))
+        self.assertTrue(mock_sftp.putfo.called)
 
     @patch('storages.backends.sftpstorage.SFTPStorage.sftp', **{
         'stat.side_effect': (FileNotFoundError(), True)
     })
     def test_save_in_subdir(self, mock_sftp):
         self.storage._save('bar/foo', File(io.BytesIO(b'foo'), 'foo'))
         self.assertEqual(mock_sftp.mkdir.call_args_list[0][0], ('bar',))
-        self.assertTrue(mock_sftp.open.return_value.write.called)
+        self.assertTrue(mock_sftp.putfo.called)
 
     @patch('storages.backends.sftpstorage.SFTPStorage.sftp')
     def test_delete(self, mock_sftp):
@@ -212,4 +218,4 @@ def test_write(self):
     def test_close(self, mock_sftp):
         self.file.write(b'foo')
         self.file.close()
-        self.assertTrue(mock_sftp.open.return_value.write.called)
+        self.assertTrue(mock_sftp.putfo.called)