relay-daemon.py

#!/usr/bin/env python

"""
Python daemon from: 
http://www.python.rk.edu.pl/w/p/proste-demony-uniksowe-w-pythonie/
"""

import sys, os, time, atexit
from signal import SIGTERM
import subprocess
import urllib
from subprocess import call

class bcolors:
    HEADER = '\033[95m'
    OKBLUE = '\033[94m'
    OKGREEN = '\033[92m'
    WARNING = '\033[93m'
    FAIL = '\033[91m'
    ENDC = '\033[0m'
    BOLD = '\033[1m'
    UNDERLINE = '\033[4m'


class Daemon:
	"""
	A generic daemon class.
	
	Usage: subclass the Daemon class and override the run() method
	"""
	def __init__(self, pidfile, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
		self.stdin = stdin
		self.stdout = stdout
		self.stderr = stderr
		self.pidfile = pidfile
	
	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)" % (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)" % (e.errno, e.strerror))
			sys.exit(1) 
	
		# redirect standard file descriptors
		sys.stdout.flush()
		sys.stderr.flush()
		si = file(self.stdin, 'r')
		so = file(self.stdout, 'a+')
		se = file(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())
		file(self.pidfile,'w+').write("%s" % pid)
	
	def delpid(self):
		os.remove(self.pidfile)

	def start(self):
		"""
		Start the daemon
		"""
		# Check for a pidfile to see if the daemon already runs
		try:
			pf = file(self.pidfile,'r')
			pid = int(pf.read().strip())
			pf.close()
		except IOError:
			pid = None
	
		if pid:
			message = "pidfile %s already exist. Daemon already running?"
			sys.stderr.write(message % self.pidfile)
			sys.exit(1)
		
		# Start the daemon
		self.daemonize()
		self.run()

	def stop(self):
		"""
		Stop the daemon
		"""
		# Get the pid from the pidfile
		try:
			pf = file(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?"
			print bcolors.WARNING + "WARNING!" + bcolors.ENDC
			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().
		"""

class MyDaemon(Daemon):
	def run(self):
		while True:
			import os
			import urllib2, urlparse, gzip
			from StringIO import StringIO
			sock = urllib.urlopen("http://[your server address]/[replace with your chip id]?token=your_token&uptime=your_uptime_in_s")
			htmlSource = sock.read()
			sock.close()
			if htmlSource[0] == "1":
				os.system("gpio -g write [your GPIO number] 1")
			else:
				os.system("gpio -g write [your GPIO number] 0")
			time.sleep(0.1)
			

if __name__ == "__main__":
	daemon = MyDaemon('/tmp/daemon-example.pid')
	if len(sys.argv) == 2:
		if 'start' == sys.argv[1]:
			print "Starting weatcher logger daemon"
			print "["+bcolors.OKGREEN + "SUCCESS" +"]"+ bcolors.ENDC
			daemon.start()
		elif 'stop' == sys.argv[1]:
			print "Stopping weatcher logger daemon"
			print "["+bcolors.OKGREEN + "SUCCESS" +"]"+ bcolors.ENDC
			daemon.stop()
		elif 'restart' == sys.argv[1]:
			print "Stopping weatcher logger daemon"
			print "Starting weatcher logger daemon"
			logfile = open('/var/log/lakewik/lakewik.log', 'a')
			logfile.write('Restarting lakewik Logger Daemon')
			logfile.close()
			daemon.restart()
			print "["+bcolors.OKGREEN + "SUCCESS" +"]"+ bcolors.ENDC
		else:
			print "["+bcolors.FAIL + "FAIL" + bcolors.ENDC+"]"+"Unknown command"
			sys.exit(2)
		sys.exit(0)
	else:
		print "usage: %s start|stop|restart" % sys.argv[0]
		sys.exit(2)