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Added daemonization option

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improved options parsing
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Matteo ℱan 2020-02-02 22:10:24 +01:00
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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import atexit
import errno
import os
import sys
import time
import signal
import logging
import argparse
from collections import Sequence
__version__ = "0.1"
__license__ = "MIT License"
__author__ = u"Matteo ℱan <SystemRage@protonmail.com>"
__copyright__ = "© Copyright 2020"
__url__ = "https://github.com/SystemRage/Etrigan"
__description__ = "Etrigan: a python daemonizer that rocks."
path = os.path.dirname(os.path.abspath(__file__))
class Etrigan(object):
"""
Daemonizer based on double-fork method
--------------------------------------
Each option can be passed as a keyword argument or modified by assigning
to an attribute on the instance:
jasonblood = Etrigan(pidfile,
argument_example_1 = foo,
argument_example_2 = bar)
that is equivalent to:
jasonblood = Etrigan(pidfile)
jasonblood.argument_example_1 = foo
jasonblood.argument_example_2 = bar
Object constructor expects always `pidfile` argument.
`pidfile`
Path to the pidfile.
The following other options are defined:
`stdin`
`stdout`
`stderr`
:Default: `os.devnull`
File objects used as the new file for the standard I/O streams
`sys.stdin`, `sys.stdout`, and `sys.stderr` respectively.
`funcs_to_daemonize`
:Default: `[]`
Define a list of your custom functions
which will be executed after daemonization.
If None, you have to subclass Etrigan `run` method.
Note that these functions can return elements that will be
added to Etrigan object (`etrigan_add` list) so the other subsequent
ones can reuse them for further processing.
You only have to provide indexes of `etrigan_add` list,
(an int (example: 2) for single index or a string (example: '1:4') for slices)
as first returning element.
`want_quit`
:Default: `False`
If `True`, runs Etrigan `quit_on_start` or `quit_on_stop`
lists of your custom functions at the end of `start` or `stop` operations.
These can return elements as `funcs_to_daemonize`.
`logfile`
:Default: `None`
Path to the output log file.
`loglevel`
:Default: `None`
Set the log level of logging messages.
`mute`
:Default: `False`
Disable all stdout and stderr messages (before double forking).
`pause_loop`
:Default: `None`
Seconds of pause between the calling, in an infinite loop,
of every function in `funcs_to_daemonize` list.
If `-1`, no pause between the calling, in an infinite loop,
of every function in `funcs_to_daemonize` list.
If `None`, only one run (no infinite loop) of functions in
`funcs_to_daemonize` list, without pause.
"""
def __init__(self, pidfile,
stdin = os.devnull, stdout = os.devnull, stderr = os.devnull,
funcs_to_daemonize = [], want_quit = False,
logfile = None, loglevel = None,
mute = False, pause_loop = None):
self.pidfile = pidfile
self.funcs_to_daemonize = funcs_to_daemonize
self.stdin = stdin
self.stdout = stdout
self.stderr = stderr
self.logfile = logfile
self.loglevel = loglevel
self.mute = mute
self.want_quit = want_quit
self.pause_loop = pause_loop
# internal only.
self.homedir = '/'
self.umask = 0o22
self.etrigan_restart, self.etrigan_reload = (False for _ in range(2))
self.etrigan_alive = True
self.etrigan_add = []
self.etrigan_index = None
# seconds of pause between stop and start during the restart of the daemon.
self.pause_restart = 5
# when terminate a process, seconds to wait until kill the process with signal.
# self.pause_kill = 3
# create logfile.
self.setup_files()
def handle_terminate(self, signum, frame):
if os.path.exists(self.pidfile):
self.etrigan_alive = False
# eventually run quit (on stop) function/s.
if self.want_quit:
if not isinstance(self.quit_on_stop, (list, tuple)):
self.quit_on_stop = [self.quit_on_stop]
self.execute(self.quit_on_stop)
# then always run quit standard.
self.quit_standard()
else:
self.view(self.logdaemon.error, self.emit_error, "Failed to stop the daemon process: can't find PIDFILE '%s'" %self.pidfile)
sys.exit(0)
def handle_reload(self, signum, frame):
self.etrigan_reload = True
def setup_files(self):
self.pidfile = os.path.abspath(self.pidfile)
if self.logfile is not None:
self.logdaemon = logging.getLogger('logdaemon')
self.logdaemon.setLevel(self.loglevel)
filehandler = logging.FileHandler(self.logfile)
filehandler.setLevel(self.loglevel)
formatter = logging.Formatter(fmt = '[%(asctime)s] [%(levelname)8s] --- %(message)s',
datefmt = '%Y-%m-%d %H:%M:%S')
filehandler.setFormatter(formatter)
self.logdaemon.addHandler(filehandler)
else:
nullhandler = logging.NullHandler()
self.logdaemon.addHandler(nullhandler)
def emit_error(self, message, to_exit = True):
""" Print an error message to STDERR. """
if not self.mute:
sys.stderr.write(message + '\n')
sys.stderr.flush()
if to_exit:
sys.exit(1)
def emit_message(self, message, to_exit = False):
""" Print a message to STDOUT. """
if not self.mute:
sys.stdout.write(message + '\n')
sys.stdout.flush()
if to_exit:
sys.exit(0)
def view(self, logobj, emitobj, msg, **kwargs):
options = {'to_exit' : False,
'silent' : False
}
options.update(kwargs)
if logobj:
logobj(msg)
if emitobj:
if not options['silent']:
emitobj(msg, to_exit = options['to_exit'])
def daemonize(self):
"""
Double-forks the process to daemonize the script.
see Stevens' "Advanced Programming in the UNIX Environment" for details (ISBN 0201563177)
http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
"""
self.view(self.logdaemon.debug, None, "Attempting to daemonize the process...")
# First fork.
self.fork(msg = "First fork")
# Decouple from parent environment.
self.detach()
# Second fork.
self.fork(msg = "Second fork")
# Write the PID file.
self.create_pidfile()
self.view(self.logdaemon.info, self.emit_message, "The daemon process has started.")
# Redirect standard file descriptors.
sys.stdout.flush()
sys.stderr.flush()
self.attach('stdin', mode = 'r')
self.attach('stdout', mode = 'a+')
try:
self.attach('stderr', mode = 'a+', buffering = 0)
except ValueError:
# Python 3 can't have unbuffered text I/O.
self.attach('stderr', mode = 'a+', buffering = 1)
# Handle signals.
signal.signal(signal.SIGINT, self.handle_terminate)
signal.signal(signal.SIGTERM, self.handle_terminate)
signal.signal(signal.SIGHUP, self.handle_reload)
#signal.signal(signal.SIGKILL....)
def fork(self, msg):
try:
pid = os.fork()
if pid > 0:
self.view(self.logdaemon.debug, None, msg + " success with PID %d." %pid)
# Exit from parent.
sys.exit(0)
except Exception as e:
msg += " failed: %s." %str(e)
self.view(self.logdaemon.error, self.emit_error, msg)
def detach(self):
# cd to root for a guarenteed working dir.
try:
os.chdir(self.homedir)
except Exception as e:
msg = "Unable to change working directory: %s." %str(e)
self.view(self.logdaemon.error, self.emit_error, msg)
# clear the session id to clear the controlling tty.
pid = os.setsid()
if pid == -1:
sys.exit(1)
# set the umask so we have access to all files created by the daemon.
try:
os.umask(self.umask)
except Exception as e:
msg = "Unable to change file creation mask: %s." %str(e)
self.view(self.logdaemon.error, self.emit_error, msg)
def attach(self, name, mode, buffering = -1):
with open(getattr(self, name), mode, buffering) as stream:
os.dup2(stream.fileno(), getattr(sys, name).fileno())
def checkfile(self, path, typearg, typefile):
filename = os.path.basename(path)
pathname = os.path.dirname(path)
if not os.path.isdir(pathname):
msg = "argument %s: invalid directory: '%s'. Exiting..." %(typearg, pathname)
self.view(self.logdaemon.error, self.emit_error, msg)
elif not filename.lower().endswith(typefile):
msg = "argument %s: not a %s file, invalid extension: '%s'. Exiting..." %(typearg, typefile, filename)
self.view(self.logdaemon.error, self.emit_error, msg)
def create_pidfile(self):
atexit.register(self.delete_pidfile)
pid = os.getpid()
try:
with open(self.pidfile, 'w+') as pf:
pf.write("%s\n" %pid)
self.view(self.logdaemon.debug, None, "PID %d written to '%s'." %(pid, self.pidfile))
except Exception as e:
msg = "Unable to write PID to PIDFILE '%s': %s" %(self.pidfile, str(e))
self.view(self.logdaemon.error, self.emit_error, msg)
def delete_pidfile(self, pid):
# Remove the PID file.
try:
os.remove(self.pidfile)
self.view(self.logdaemon.debug, None, "Removing PIDFILE '%s' with PID %d." %(self.pidfile, pid))
except Exception as e:
if e.errno != errno.ENOENT:
self.view(self.logdaemon.error, self.emit_error, str(e))
def get_pidfile(self):
# Get the PID from the PID file.
if self.pidfile is None:
return None
if not os.path.isfile(self.pidfile):
return None
try:
with open(self.pidfile, 'r') as pf:
pid = int(pf.read().strip())
self.view(self.logdaemon.debug, None, "Found PID %d in PIDFILE '%s'" %(pid, self.pidfile))
except Exception as e:
self.view(self.logdaemon.warning, None, "Empty or broken PIDFILE")
pid = None
def pid_exists(pid):
# psutil _psposix.py.
if pid == 0:
return True
try:
os.kill(pid, 0)
except OSError as e:
if e.errno == errno.ESRCH:
return False
elif e.errno == errno.EPERM:
return True
else:
self.view(self.logdaemon.error, self.emit_error, str(e))
else:
return True
if pid is not None and pid_exists(pid):
return pid
else:
# Remove the stale PID file.
self.delete_pidfile(pid)
return None
def start(self):
""" Start the daemon. """
self.view(self.logdaemon.info, self.emit_message, "Starting the daemon process...", silent = self.etrigan_restart)
# Check for a PID file to see if the Daemon is already running.
pid = self.get_pidfile()
if pid is not None:
msg = "A previous daemon process with PIDFILE '%s' already exists. Daemon already running ?" %self.pidfile
self.view(self.logdaemon.warning, self.emit_error, msg, to_exit = False)
return
# Daemonize the main process.
self.daemonize()
# Start a infinitive loop that periodically runs `funcs_to_daemonize`.
self.loop()
# eventualy run quit (on start) function/s.
if self.want_quit:
if not isinstance(self.quit_on_start, (list, tuple)):
self.quit_on_start = [self.quit_on_start]
self.execute(self.quit_on_start)
def stop(self):
""" Stop the daemon. """
self.view(None, self.emit_message, "Stopping the daemon process...", silent = self.etrigan_restart)
self.logdaemon.disabled = True
pid = self.get_pidfile()
self.logdaemon.disabled = False
if not pid:
# Just to be sure. A ValueError might occur
# if the PIDFILE is empty but does actually exist.
if os.path.exists(self.pidfile):
self.delete_pidfile(pid)
msg = "Can't find the daemon process with PIDFILE '%s'. Daemon not running ?" %self.pidfile
self.view(self.logdaemon.warning, self.emit_error, msg, to_exit = False)
return
# Try to kill the daemon process.
try:
while True:
os.kill(pid, signal.SIGTERM)
time.sleep(0.1)
except Exception as e:
if (e.errno != errno.ESRCH):
self.view(self.logdaemon.error, self.emit_error, "Failed to stop the daemon process: %s" %str(e))
else:
self.view(None, self.emit_message, "The daemon process has ended correctly.", silent = self.etrigan_restart)
def restart(self):
""" Restart the daemon. """
self.view(self.logdaemon.info, self.emit_message, "Restarting the daemon process...")
self.etrigan_restart = True
self.stop()
if self.pause_restart:
time.sleep(self.pause_restart)
self.etrigan_alive = True
self.start()
def reload(self):
pass
def status(self):
""" Get status of the daemon. """
self.view(self.logdaemon.info, self.emit_message, "Viewing the daemon process status...")
if self.pidfile is None:
self.view(self.logdaemon.error, self.emit_error, "Cannot get the status of daemon without PIDFILE.")
pid = self.get_pidfile()
if pid is None:
self.view(self.logdaemon.info, self.emit_message, "The daemon process is not running.", to_exit = True)
else:
try:
with open("/proc/%d/status" %pid, 'r') as pf:
pass
self.view(self.logdaemon.info, self.emit_message, "The daemon process is running.", to_exit = True)
except Exception as e:
msg = "There is not a process with the PIDFILE '%s': %s" %(self.pidfile, str(e))
self.view(self.logdaemon.error, self.emit_error, msg)
def flatten(self, alistoflists, ltypes = Sequence):
# https://stackoverflow.com/questions/2158395/flatten-an-irregular-list-of-lists/2158532#2158532
alistoflists = list(alistoflists)
while alistoflists:
while alistoflists and isinstance(alistoflists[0], ltypes):
alistoflists[0:1] = alistoflists[0]
if alistoflists: yield alistoflists.pop(0)
def exclude(self, func):
from inspect import getargspec
args = getargspec(func)
if callable(func):
try:
args[0].pop(0)
except IndexError:
pass
return args
else:
self.view(self.logdaemon.error, self.emit_error, "Not a function.")
return
def execute(self, some_functions):
returned = None
if isinstance(some_functions, (list, tuple)):
for func in some_functions:
l_req = len(self.exclude(func)[0])
if l_req == 0:
returned = func()
else:
l_add = len(self.etrigan_add)
if l_req > l_add:
self.view(self.logdaemon.error, self.emit_error,
"Can't evaluate function: given %s, required %s." %(l_add, l_req))
return
else:
arguments = self.etrigan_add[self.etrigan_index]
l_args = (len(arguments) if isinstance(arguments, list) else 1)
if (l_args > l_req) or (l_args < l_req):
self.view(self.logdaemon.error, self.emit_error,
"Can't evaluate function: given %s, required %s." %(l_args, l_req))
return
else:
if isinstance(arguments, list):
returned = func(*arguments)
else:
returned = func(arguments)
if returned:
if isinstance(returned, (list, tuple)):
if isinstance(returned[0], int):
self.etrigan_index = returned[0]
else:
self.etrigan_index = slice(*map(int, returned[0].split(':')))
if returned[1:] != []:
self.etrigan_add.append(returned[1:])
self.etrigan_add = list(self.flatten(self.etrigan_add))
else:
self.view(self.logdaemon.error, self.emit_error, "Function should return list or tuple.")
returned = None
else:
if some_functions is None:
self.run()
def loop(self):
try:
if self.pause_loop is None:
# one-shot.
self.execute(self.funcs_to_daemonize)
else:
if self.pause_loop >= 0:
# infinite with pause.
time.sleep(self.pause_loop)
while self.etrigan_alive:
self.execute(self.funcs_to_daemonize)
time.sleep(self.pause_loop)
elif self.pause_loop == -1:
# infinite without pause.
while self.etrigan_alive:
self.execute(self.funcs_to_daemonize)
except Exception as e:
msg = "The daemon process start method failed: %s" %str(e)
self.view(self.logdaemon.error, self.emit_error, msg)
def quit_standard(self):
self.view(self.logdaemon.info, None, "Stopping the daemon process...")
self.delete_pidfile(self.get_pidfile())
self.view(self.logdaemon.info, None, "The daemon process has ended correctly.")
def quit_on_start(self):
"""
Override this method when you subclass Daemon.
"""
self.quit_standard()
def quit_on_stop(self):
"""
Override this method when you subclass Daemon.
"""
pass
def run(self):
"""
Override this method when you subclass Daemon.
It will be called after the process has been
daemonized by start() or restart().
"""
pass
#-----------------------------------------------------------------------------------------------------------------------------------------------------------
class JasonBlood(Etrigan):
def run(self):
jasonblood_func()
def jasonblood_func():
with open(os.path.join(path, 'etrigan_test.txt'), 'a') as file:
file.write("Yarva Demonicus Etrigan " + time.strftime("%Y-%m-%d %H:%M:%S", time.gmtime()) + '\n')
def Etrigan_parser(parser = None):
if parser is None:
# create a new parser.
parser = argparse.ArgumentParser(description = __description__, epilog = __version__)
if not parser.add_help:
# create help argument.
parser.add_argument("-h", "--help", action = "help", help = "show this help message and exit")
# attach to an existent parser.
parser.add_argument("operation", action = "store", choices = ["start", "stop", "restart", "status", "reload"],
help = "Select an operation for daemon.", type = str)
parser.add_argument("--etrigan-pid",
action = "store", dest = "etriganpid", default = "/tmp/etrigan.pid",
help = "Choose a pidfile path. Default is \"/tmp/etrigan.pid\".", type = str) #'/var/run/etrigan.pid'
parser.add_argument("--etrigan-log",
action = "store", dest = "etriganlog", default = os.path.join(path, "etrigan.log"),
help = "Use this option to choose an output log file; for not logging don't select it. Default is \"etrigan.log\".", type = str)
parser.add_argument("--etrigan-lev",
action = "store", dest = "etriganlev", default = "DEBUG",
choices = ["CRITICAL", "ERROR", "WARNING", "INFO", "DEBUG"],
help = "Use this option to set a log level. Default is \"DEBUG\".", type = str)
parser.add_argument("--etrigan-mute",
action = "store_const", dest = 'etriganmute', const = True, default = False,
help = "Disable all stdout and stderr messages.")
return parser
class Etrigan_check(object):
def emit_opt_err(self, msg):
print(msg)
sys.exit(1)
def checkfile(self, path, typearg, typefile):
filename, extension = os.path.splitext(path)
pathname = os.path.dirname(path)
if not os.path.isdir(pathname):
msg = "argument `%s`: invalid directory: '%s'. Exiting..." %(typearg, pathname)
self.emit_opt_err(msg)
elif not extension == typefile:
msg = "argument `%s`: not a %s file, invalid extension: '%s'. Exiting..." %(typearg, typefile, extension)
self.emit_opt_err(msg)
def checkfunction(self, funcs, booleans):
if not isinstance(funcs, (list, tuple)):
if funcs is not None:
msg = "argument `funcs_to_daemonize`: provide list, tuple or None"
self.emit_opt_err(msg)
for elem in booleans:
if not type(elem) == bool:
msg = "argument `want_quit`: not a boolean."
self.emit_opt_err(msg)
def Etrigan_job(type_oper, daemon_obj):
Etrigan_check().checkfunction(daemon_obj.funcs_to_daemonize,
[daemon_obj.want_quit])
if type_oper == "start":
daemon_obj.start()
elif type_oper == "stop":
daemon_obj.stop()
elif type_oper == "restart":
daemon_obj.restart()
elif type_oper == "status":
daemon_obj.status()
elif type_oper == "reload":
daemon_obj.reload()
sys.exit(0)
def main():
# Parse arguments.
parser = Etrigan_parser()
args = vars(parser.parse_args())
# Check arguments.
Etrigan_check().checkfile(args['etriganpid'], 'pidfile', '.pid')
Etrigan_check().checkfile(args['etriganlog'], 'pidfile', '.log')
# Setup daemon.
jasonblood_1 = Etrigan(pidfile = args['etriganpid'], logfile = args['etriganlog'], loglevel = args['etriganlev'],
mute = args['etriganmute'],
funcs_to_daemonize = [jasonblood_func], pause_loop = 5)
## jasonblood_2 = JasonBlood(pidfile = args['etriganpid'], logfile = args['etriganlog'], loglevel = args['etriganlev'],
## mute = args['etriganmute'],
## funcs_to_daemonize = None, pause_loop = 5)
# Do job.
Etrigan_job(args['operation'], jasonblood_1)
if __name__ == '__main__':
main()