stop image downloads to memory

 + Fixes issue with large images hogging memory
 + stream image downloads
 + output to stdout if file not specified

Change-Id: Ia01ff9b21a2dac5d0ccf2bd58a8640e88c5cbb36
Story: 2007672
Task: 39776

Author: Simon Merrick

openstackclient/image/v1/image.py

@@ -478,7 +478,11 @@ def take_action(self, parsed_args):
         image_client = self.app.client_manager.image
         image = image_client.find_image(parsed_args.image)
 
-        image_client.download_image(image.id, output=parsed_args.file)
+        output_file = parsed_args.file
+        if output_file is None:
+            output_file = getattr(sys.stdout, "buffer", sys.stdout)
+
+        image_client.download_image(image.id, stream=True, output=output_file)
 
 
 class SetImage(command.Command):

openstackclient/image/v2/image.py

@@ -803,7 +803,11 @@ def take_action(self, parsed_args):
         image_client = self.app.client_manager.image
         image = image_client.find_image(parsed_args.image)
 
-        image_client.download_image(image.id, output=parsed_args.file)
+        output_file = parsed_args.file
+        if output_file is None:
+            output_file = getattr(sys.stdout, "buffer", sys.stdout)
+
+        image_client.download_image(image.id, stream=True, output=output_file)
 
 
 class SetImage(command.Command):

openstackclient/tests/unit/image/v2/test_image.py

@@ -1618,14 +1618,15 @@ def test_save_data(self):
 
         verifylist = [
             ('file', '/path/to/file'),
-            ('image', self.image.id)
+            ('image', self.image.id),
         ]
         parsed_args = self.check_parser(self.cmd, arglist, verifylist)
 
         self.cmd.take_action(parsed_args)
 
         self.client.download_image.assert_called_once_with(
             self.image.id,
+            stream=True,
             output='/path/to/file')
 
 

releasenotes/notes/fix-openstak-image-save-sdk-port-eb160e8ffc92e514.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - Stream image download to avoid buffering data in memory which rapidly
+    exhausts memory resulting in OOM kill or system crash for all but the
+    smallest of images. Fixes https://storyboard.openstack.org/#!/story/2007672
+  - Restore default behavior of 'openstack image save' to send data to stdout
+    Relates to https://storyboard.openstack.org/#!/story/2007672.