def daemonize(self):
"""Creates the daemon.
It will fork a child process and then exit parent. By performing a
double fork, set the current process's user id, change the current
working directory, set the current numeric umask, redirect standard
streams and write the pid to a file.
"""
def redirect_stream(system_stream, target_stream):
"""Redirect a system stream to a specified file.
"""
if target_stream is None:
target_f = os.open(os.devnull, os.O_RDWR)
else:
target_f = target_stream.fileno()
os.dup2(target_f, system_stream.fileno())
def fork_then_exit_parent(error_message):
"""Fork a child process, then exit the parent process.
"""
try:
pid = os.fork()
if pid > 0:
os._exit(0) # pylint: disable=W0212
except OSError as err:
msg = "{0}: [{1}] {2}".format(error_message, err.errno,
err.strerror)
self._report(msg, logging.CRITICAL)
raise UtilDaemonError(msg)
# Fork
fork_then_exit_parent("Failed first fork.")
try:
os.setsid()
os.chdir(self.chdir)
os.umask(self.umask)
except Exception as err:
msg = "Unable to change directory ({0})".format(err)
self._report(msg, logging.CRITICAL)
raise UtilDaemonError(msg)
# Double fork
fork_then_exit_parent("Failed second fork.")
# Redirect streams
redirect_stream(sys.stdin, self.stdin)
redirect_stream(sys.stdout, self.stdout)
redirect_stream(sys.stderr, self.stderr)
# write pidfile
atexit.register(self.delete_pidfile)
pid = str(os.getpid())
try:
with open(self.pidfile, "w") as f:
f.write("{0}\n".format(pid))
except IOError as err:
msg = "Unable to write pidfile: {0}".format(err.strerror)
self._report(msg, logging.CRITICAL)
raise UtilDaemonError(msg)
def start(self, detach_process=True):
"""Starts the daemon.
It will start the daemon if detach_process is True.
"""
if detach_process:
# Check for a pidfile presence
try:
with open(self.pidfile, "rb") as f:
self.pid = int(f.read().strip())
except IOError:
self.pid = None
except SystemExit:
self.pid = None
except ValueError:
self.pid = None
if self.pid:
# Daemon already runs
msg = ("pidfile {0} already exists. The daemon is already "
"running?".format(self.pidfile))
self._report(msg, logging.CRITICAL)
raise UtilDaemonError(msg)
# Start the daemon
self.daemonize()
# Run automatic failover
return self.run()
def stop(self):
"""Stops the daemon.
It will stop the daemon by sending a signal.SIGTERM to the process.
"""
# Get the pid from the pidfile
try:
with open(self.pidfile, "rb") as f:
self.pid = int(f.read().strip())
except IOError:
self._report("pidfile {0} does not exist.".format(self.pidfile),
logging.ERROR)
return False
except ValueError:
self._report("Invalid pid in pidfile {0}.".format(self.pidfile),
logging.ERROR)
return False
# Kill the daemon process
try:
while 1:
os.kill(self.pid, signal.SIGTERM)
time.sleep(0.1)
except OSError as err:
strerror = err.strerror
if err.errno == 3: # No such process
if os.path.exists(self.pidfile):
self.delete_pidfile()
else:
msg = "Unable to delete pidfile: {0}".format(strerror)
self._report(msg, logging.ERROR)
raise UtilDaemonError(msg)
return True
def delete_pidfile(self):
"""Deletes pidfile.
"""
try:
os.remove(self.pidfile)
except (OSError, IOError) as err:
msg = "Unable to delete pidfile: {0}".format(err.strerror)
self._report(msg, logging.ERROR)
raise UtilDaemonError(msg)
def fork_then_exit_parent(error_message):
"""Fork a child process, then exit the parent process.
"""
try:
pid = os.fork()
if pid > 0:
os._exit(0) # pylint: disable=W0212
except OSError as err:
msg = "{0}: [{1}] {2}".format(error_message, err.errno,
err.strerror)
self._report(msg, logging.CRITICAL)
raise UtilDaemonError(msg)