rattail/rattail/daemon.py
Lance Edgar 177478f7d0 Database config/init overhaul.
This contains some not-very-atomic changes:

* Get rid of `get_session_class()` function and return to global `Session`
  class approach.
* Primary database `Session` is now configured as part of command
  initialization, by default.
* Make `config` object available to subcommands, and `Daemon` instances
  (the beginning of the end for `edbob.config`!).
* Add `--stdout` and `--stderr` arguments to primary `Command`.  These are
  in turn made available to subcommands.
* Overhauled some subcommand logic per new patterns.
* Get rid of a few other random references to `edbob`.
* Added and improved several tests.
* Added ability to run tests using arbitrary database engine.
2014-02-15 16:13:39 -08:00

140 lines
3.9 KiB
Python

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# This code was (mostly, with some tweaks) stolen from:
# http://www.jejik.com/articles/2007/02/a_simple_unix_linux_daemon_in_python/
import sys, os, time, atexit
import stat
from signal import SIGTERM
class Daemon(object):
"""
A generic daemon class.
Usage: subclass the Daemon class and override the run() method
"""
def __init__(self, pidfile, config=None, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
self.pidfile = pidfile
self.config = config
self.stdin = stdin
self.stdout = stdout
self.stderr = stderr
def daemonize(self):
"""
do the UNIX double-fork magic, see Stevens' "Advanced
Programming in the UNIX Environment" for details (ISBN 0201563177)
http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
"""
try:
pid = os.fork()
if pid > 0:
# exit first parent
sys.exit(0)
except OSError, e:
sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))
sys.exit(1)
# decouple from parent environment
os.chdir("/")
os.setsid()
os.umask(0)
# do second fork
try:
pid = os.fork()
if pid > 0:
# exit from second parent
sys.exit(0)
except OSError, e:
sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
sys.exit(1)
# redirect standard file descriptors
sys.stdout.flush()
sys.stderr.flush()
si = open(self.stdin, 'r')
so = open(self.stdout, 'a+')
se = open(self.stderr, 'a+', 0)
os.dup2(si.fileno(), sys.stdin.fileno())
os.dup2(so.fileno(), sys.stdout.fileno())
os.dup2(se.fileno(), sys.stderr.fileno())
# write pidfile
atexit.register(self.delpid)
pid = str(os.getpid())
with open(self.pidfile, 'w+') as f:
f.write('{0}\n'.format(pid))
os.chmod(self.pidfile, stat.S_IRUSR|stat.S_IWUSR)
def delpid(self):
if os.path.exists(self.pidfile):
os.remove(self.pidfile)
def start(self, daemonize=True):
"""
Start the daemon
"""
# Check for a pidfile to see if the daemon already runs
try:
pf = open(self.pidfile,'r')
pid = int(pf.read().strip())
pf.close()
except IOError:
pid = None
if pid:
message = "pidfile %s already exist. Daemon already running?\n"
sys.stderr.write(message % self.pidfile)
sys.exit(1)
# Start the daemon
if daemonize:
self.daemonize()
self.run()
def stop(self):
"""
Stop the daemon
"""
# Get the pid from the pidfile
try:
pf = open(self.pidfile,'r')
pid = int(pf.read().strip())
pf.close()
except IOError:
pid = None
if not pid:
message = "pidfile %s does not exist. Daemon not running?\n"
sys.stderr.write(message % self.pidfile)
return # not an error in a restart
# Try killing the daemon process
try:
while 1:
os.kill(pid, SIGTERM)
time.sleep(0.1)
except OSError, err:
err = str(err)
if err.find("No such process") > 0:
if os.path.exists(self.pidfile):
os.remove(self.pidfile)
else:
print str(err)
sys.exit(1)
def restart(self):
"""
Restart the daemon
"""
self.stop()
self.start()
def run(self):
"""
You should override this method when you subclass Daemon. It will be called after the process has been
daemonized by start() or restart().
"""