There is an issue with mysql init.d script that redirects stdout of a process run in the background. This leads to subprocess.Popen process with file descriptor that was piped to a stream from child process existing after child process has exited with 0. Because it's state wasn't checked by parent (it tries to read from that file descriptor) we have one process hanged and another one in defunct state
How to reproduce:
#!/usr/bin/python
import os
import subprocess
args = [
'apt-get', '-q', '-y',
'-o', 'DPkg::Options::=--force-confold',
'-o', 'DPkg::Options::=--force-confdef',
'install', 'mysql-server-wsrep-5.6']
kwargs = {
'shell': False,
'env': {
'LC_NUMERIC': 'C',
'LC_ADDRESS': 'C',
'DEBIAN_FRONTEND': 'noninteractive',
'LC_MEASUREMENT': 'C',
'LC_CTYPE': 'C',
'UPSTART_JOB': 'salt-minion',
'LC_PAPER': 'C',
'PATH': '/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/sbin:/sbin:/bin',
'UCF_FORCE_CONFFOLD': '1',
'APT_LISTCHANGES_FRONTEND': 'none',
'LC_IDENTIFICATION': 'C',
'TERM': 'linux',
'LC_MESSAGES': 'C',
'LC_MONETARY': 'C',
'LC_COLLATE': 'C',
'LC_TELEPHONE': 'C',
'UPSTART_INSTANCE': '',
'PWD': '/',
'LC_NAME': 'C',
'LC_TIME': 'C',
'APT_LISTBUGS_FRONTEND': 'none',
},
'close_fds': True,
'stdout': -1,
'stderr': -1,
'cwd': '/root',
}
print('Creating process')
process = subprocess.Popen(args, **kwargs)
print('Communicating with process')
stdout, stderr = process.communicate(input=None)
Couldn't reproduce into clean docker image. Need more data.