/usr/lib/python2.7/dist-packages/application/process.py is in python-application 1.4.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 | # Copyright (C) 2006-2012 Dan Pascu. See LICENSE for details.
#
"""UNIX process and signal management"""
__all__ = ['Process', 'ProcessError', 'Signals', 'process']
import sys
import os
import errno
import signal
import atexit
from application import log
from application.python.types import Singleton
class ProcessError(Exception): pass
class Process(object):
"""Control how the current process runs and interacts with the operating system"""
__metaclass__ = Singleton
def __init__(self):
self._daemon = False
self._pidfile = None
self.signals = Signals()
self._runtime_directory = '/var/run'
self._system_config_directory = '/etc'
self._local_config_directory = os.path.realpath(os.path.dirname(sys.argv[0]))
def _get_local_config_directory(self):
return self._local_config_directory
def _set_local_config_directory(self, path):
self._local_config_directory = os.path.realpath(path)
local_config_directory = property(_get_local_config_directory, _set_local_config_directory)
def _get_system_config_directory(self):
return self._system_config_directory
def _set_system_config_directory(self, path):
self._system_config_directory = os.path.realpath(path)
system_config_directory = property(_get_system_config_directory, _set_system_config_directory)
def _get_runtime_directory(self):
return self._runtime_directory
def _set_runtime_directory(self, path):
path = os.path.realpath(path)
if not os.path.isdir(path):
try:
os.makedirs(path)
except OSError, e:
raise ProcessError("cannot set runtime directory to %s: %s" % (path, e.args[1]))
if not os.access(path, os.X_OK | os.W_OK):
raise ProcessError("runtime directory %s is not writable" % path)
self._runtime_directory = path
runtime_directory = property(_get_runtime_directory, _set_runtime_directory)
def _check_if_running(self):
"""Check if the process is already running"""
pidfile = self._pidfile
if pidfile is None or not os.path.isfile(pidfile):
return
try:
pf = open(pidfile, 'rb')
except IOError, why:
raise ProcessError("unable to open pidfile %s: %s" % (pidfile, str(why)))
else:
try:
try:
pid = int(pf.readline().strip())
except IOError, why:
raise ProcessError("unable to read pidfile %s: %s" % (pidfile, str(why)))
except ValueError:
pass
else:
## Check if the process identified by pid is running
## Send the process a signal of zero (0)
try:
os.kill(pid, 0)
except OSError, why:
if why[0] in (errno.EPERM, errno.EACCES):
raise ProcessError("already running with pid %d" % pid)
else:
raise ProcessError("already running with pid %d" % pid)
finally:
pf.close()
def _do_fork(self):
"""Perform the Unix double fork"""
## First fork.
## This will return control to the command line/shell that invoked us and
## will guarantee that the forked child will not be a process group leader
## (which is required for setsid() below to succeed).
try:
pid = os.fork()
if pid > 0:
sys.exit(0) ## exit parent
#os._exit(0)
except OSError, e:
raise ProcessError("fork #1 failed: %d: %s" % (e.errno, e.strerror))
## Decouple from the controling terminal.
## Calling setsid() we become a process group and session group leader.
## Since a controlling terminal is associated with a session, and this
## new session has not yet acquired a controlling terminal our process
## now has no controlling terminal, which is a Good Thing for daemons.
os.setsid()
## Second fork
## This will allow the parent (the session group leader obtained above)
## to exit. This means that the child, as a non-session group leader,
## can never regain a controlling terminal.
try:
pid = os.fork()
if pid > 0:
sys.exit(0) ## exit 1st child too
#os._exit(0)
except OSError, e:
raise ProcessError("fork #2 failed: %d: %s" % (e.errno, e.strerror))
## Setup our environment.
## Change working directory to / so we do not keep any directory in use
## preventing them from being unmounted. Also set file creation mask.
os.chdir("/")
os.umask(022)
def _make_pidfile(self):
"""Create the pidfile if defined"""
if not self._pidfile:
return
try:
pf = open(self._pidfile, "wb")
try:
pf.write("%s\n" % os.getpid())
finally:
pf.close()
except IOError, e:
raise ProcessError("unable to write pidfile %s: %s" % (self._pidfile, str(e)))
def _redirect_stdio(self):
"""Redirect stdin, stdout and stderr to /dev/null"""
sys.stdout.flush()
sys.stderr.flush()
null = os.open('/dev/null', os.O_RDWR)
os.dup2(null, sys.stdin.fileno())
os.dup2(null, sys.stdout.fileno())
os.dup2(null, sys.stderr.fileno())
os.close(null)
def _setup_signal_handlers(self):
"""Setup the signal handlers for daemon mode"""
signals = self.signals
## Ignore Terminal I/O Signals
if hasattr(signal, 'SIGTTOU'):
signals.ignore(signal.SIGTTOU)
if hasattr(signal, 'SIGTTIN'):
signals.ignore(signal.SIGTTIN)
if hasattr(signal, 'SIGTSTP'):
signals.ignore(signal.SIGTSTP)
## Ignore USR signals
if hasattr(signal, 'SIGUSR1'):
signals.ignore(signal.SIGUSR1)
if hasattr(signal, 'SIGUSR2'):
signals.ignore(signal.SIGUSR2)
def __on_exit(self):
if self._pidfile:
try:
os.unlink(self._pidfile)
except OSError, why:
log.warn("unable to delete pidfile %s: %s" % (self._pidfile, str(why)))
def daemonize(self, pidfile=None):
"""Detach from terminal and run in the background"""
if self._daemon:
raise ProcessError('already in daemon mode')
self._daemon = True
if pidfile:
self._pidfile = self.runtime_file(pidfile)
self._check_if_running()
self._do_fork()
self._make_pidfile()
self._redirect_stdio()
self._setup_signal_handlers()
atexit.register(self.__on_exit)
def get_config_directories(self):
"""Return a tuple containing the system and local config directories."""
return (self._system_config_directory, self._local_config_directory)
def config_file(self, name):
"""Return a config file name. Lookup order: name if absolute, local_dir/name, system_dir/name, None if none found"""
path = os.path.realpath(os.path.join(self._local_config_directory, name))
if os.path.isfile(path) and os.access(path, os.R_OK):
return path
path = os.path.realpath(os.path.join(self._system_config_directory, name))
if os.path.isfile(path) and os.access(path, os.R_OK):
return path
return None
def runtime_file(self, name):
"""Return a runtime file name (prepends runtime_directory if defined and name is not absolute, else name)."""
if name is None:
return None
if self.runtime_directory is not None:
return os.path.realpath(os.path.join(self.runtime_directory, name))
else:
return os.path.realpath(name)
class Signals(object):
"""Interface to the system signals"""
__metaclass__ = Singleton
def __init__(self):
self._handlers = {}
if not hasattr(signal, '_original_signal'):
signal._original_signal = signal.signal
def __dispatcher(self, signum, frame):
for handler in self._handlers.get(signum, []):
handler(signum, frame)
def add_handler(self, signum, sighandler):
"""Add handler to handler list for signal"""
if not callable(sighandler):
raise RuntimeError("signal handler needs to be a callable")
self._handlers.setdefault(signum, set()).add(sighandler)
if signal.getsignal(signum) != self.__dispatcher:
signal._original_signal(signum, self.__dispatcher)
def ignore(self, signum):
"""Ignore signal"""
signal._original_signal(signum, signal.SIG_IGN)
try:
del self._handlers[signum]
except KeyError:
pass
def default_handler(self, signum):
"""Use default handler for signal"""
signal._original_signal(signum, signal.SIG_DFL)
try:
del self._handlers[signum]
except KeyError:
pass
def steal_handlers(self, enable):
"""Replace signal() from the signal module with add_handler()"""
if enable:
signal.signal = self.add_handler
else:
signal.signal = signal._original_signal
process = Process()
|