Used subprocess check_output for docker save

The docker save command is what creates the tar of the container
image. For larger images the pipe buffer is too small. So using
subprocess.check_output to get the result of docker save.

- Moved logic to check for sudo use in is_sudo function
- Added function docker_command_check for use of
subprocess.check_output to fork processes
- Used docker_command_check in the extract_image_metadata function

Resolves tern-tools#69

Signed-off-by: Nisha K <[email protected]>

utils/container.py

@@ -43,18 +43,23 @@
 logger = logging.getLogger(logger_name)
 
 
-def docker_command(command, *extra):
- '''Invoke docker command. If the command fails nothing is returned
- If it passes then the result is returned'''
- full_cmd = []
+def is_sudo():
+ '''Check if the user uses sudo for docker commands'''
  sudo = True
  try:
  members = grp.getgrnam('docker').gr_mem
  if pwd.getpwuid(os.getuid()).pw_name in members:
  sudo = False
  except KeyError:
  pass
- if sudo:
+ return sudo
+
+
+def docker_command(command, *extra):
+ '''Invoke docker command. If the command fails nothing is returned
+ If it passes then the result is returned'''
+ full_cmd = []
+ if is_sudo():
  full_cmd.append('sudo')
  full_cmd.extend(command)
  for arg in extra:
@@ -70,6 +75,23 @@ def docker_command(command, *extra):
  return result
 
 
+def docker_command_check(command, *extra):
+ '''Invoke docker command using subprocess.check_output'''
+ full_cmd = []
+ if is_sudo():
+ full_cmd.append('sudo')
+ full_cmd.extend(command)
+ for arg in extra:
+ full_cmd.append(arg)
+ # invoke
+ logger.debug("Running command: " + ' '.join(full_cmd))
+ try:
+ result = subprocess.check_output(full_cmd)
+ return result
+ except subprocess.CalledProcessError:
+ raise
+
+
 def check_container():
  '''Check if a container exists'''
  is_container = False
@@ -155,7 +177,7 @@ def get_image_id(image_tag_string):
 def extract_image_metadata(image_tag_string):
  '''Run docker save and extract the files in a temporary directory'''
  temp_path = os.path.abspath(temp_folder)
- result = docker_command(save, image_tag_string)
+ result = docker_command_check(save, image_tag_string)
  with tarfile.open(fileobj=io.BytesIO(result)) as tar:
  tar.extractall(temp_path)
  if not os.path.exists(temp_path):