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 <silbe@linux.vnet.ibm.com> Reviewed-by: Janosch Frank <frankja@linux.vnet.ibm.com> Message-Id: <1473192351-601-2-git-send-email-silbe@linux.vnet.ibm.com> Signed-off-by: Fam Zheng <famz@redhat.com>
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@ -25,6 +25,10 @@ from tarfile import TarFile, TarInfo
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from StringIO import StringIO
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from shutil import copy, rmtree
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DEVNULL = open(os.devnull, 'wb')
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def _text_checksum(text):
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"""Calculate a digest string unique to the text content"""
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return hashlib.sha1(text).hexdigest()
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@ -34,8 +38,7 @@ def _guess_docker_command():
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commands = [["docker"], ["sudo", "-n", "docker"]]
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for cmd in commands:
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if subprocess.call(cmd + ["images"],
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stdout=subprocess.PIPE,
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stderr=subprocess.PIPE) == 0:
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stdout=DEVNULL, stderr=DEVNULL) == 0:
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return cmd
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commands_txt = "\n".join([" " + " ".join(x) for x in commands])
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raise Exception("Cannot find working docker command. Tried:\n%s" % \
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@ -98,7 +101,7 @@ class Docker(object):
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def _do(self, cmd, quiet=True, infile=None, **kwargs):
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if quiet:
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kwargs["stdout"] = subprocess.PIPE
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kwargs["stdout"] = DEVNULL
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if infile:
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kwargs["stdin"] = infile
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return subprocess.call(self._command + cmd, **kwargs)
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