From: Sascha Silbe Date: Tue, 6 Sep 2016 20:05:44 +0000 (+0200) Subject: docker.py: don't hang on large docker output X-Git-Tag: v2.8.0-rc0~152^2~7 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=c977257045fdb90f98b92b9e08daa8ace378650b;p=qemu-xen-unstable.git docker.py: don't hang on large docker output 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 Reviewed-by: Janosch Frank Message-Id: <1473192351-601-2-git-send-email-silbe@linux.vnet.ibm.com> Signed-off-by: Fam Zheng --- diff --git a/tests/docker/docker.py b/tests/docker/docker.py index 222a1053fe..efb2bf4ac2 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') + + 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)