On Wed, 08/24 20:30, Sascha Silbe wrote:
> Unlike Popen.communicate(), subprocess.call() doesn't read from the
> stdout file descriptor. If the child process produces more output than
> fits into the pipe buffer, it will block indefinitely.
>
> If we don't intend to consume the output, just send it straight to
> /dev/null to avoid this issue.
>
> Signed-off-by: Sascha Silbe <si...@linux.vnet.ibm.com>
> Reviewed-by: Janosch Frank <fran...@linux.vnet.ibm.com>
> ---
> This fixes a hang for me when building the Ubuntu docker image (empty
> docker image cache).
>
> tests/docker/docker.py | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/tests/docker/docker.py b/tests/docker/docker.py
> index 222a105..efb2bf4 100755
> --- a/tests/docker/docker.py
> +++ b/tests/docker/docker.py
> @@ -25,6 +25,10 @@ from tarfile import TarFile, TarInfo
> from StringIO import StringIO
> from shutil import copy, rmtree
>
> +
> +DEVNULL = open(os.devnull, 'wb')
> +
> +
Too many blank lines? Otherwise looks good.
> def _text_checksum(text):
> """Calculate a digest string unique to the text content"""
> return hashlib.sha1(text).hexdigest()
> @@ -34,8 +38,7 @@ def _guess_docker_command():
> commands = [["docker"], ["sudo", "-n", "docker"]]
> for cmd in commands:
> if subprocess.call(cmd + ["images"],
> - stdout=subprocess.PIPE,
> - stderr=subprocess.PIPE) == 0:
> + stdout=DEVNULL, stderr=DEVNULL) == 0:
> return cmd
> commands_txt = "\n".join([" " + " ".join(x) for x in commands])
> raise Exception("Cannot find working docker command. Tried:\n%s" % \
> @@ -98,7 +101,7 @@ class Docker(object):
>
> def _do(self, cmd, quiet=True, infile=None, **kwargs):
> if quiet:
> - kwargs["stdout"] = subprocess.PIPE
> + kwargs["stdout"] = DEVNULL
> if infile:
> kwargs["stdin"] = infile
> return subprocess.call(self._command + cmd, **kwargs)
> --
> 1.9.1
>
