seisDataLoggerDaemon.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys, os, atexit, logging, time
from time import strftime
from signal import SIGTERM 
import ConfigParser as cp

class Daemon:
	"""
	A generic daemon class.
	
	Usage: subclass the Daemon class and override the run() method
	"""
	def __init__(self, pidfile, stdin='/dev/null', \
	             stdout='/srv/tc1/log/daemon.out.log', \
	             stderr='/srv/tc1/log/daemon.err.log'):
		self.stdin = stdin
		self.stdout = stdout
		self.stderr = stderr
		self.pidfile = pidfile
		
		# Read and parse the config file.
		self.config = cp.RawConfigParser()
		self.config.read("/srv/tc1/conf/datalogger.props.cfg")
		
		# Set up logger
		logpath = self.config.get("logging","logpath")
		self.logger = logging.getLogger()
		self.logger.setLevel(logging.DEBUG)
		self.logger.addHandler(logging.FileHandler(logpath+"seisDataLogger.log"))
	
	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 = 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\n" % 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?\n"
			sys.stderr.write(message % self.pidfile)
			sys.exit(1)
		
		# Start the daemon
		self.daemonize()  
		
		# Write log header
		self.logger.info("-----------------------------------------")
		self.logger.info("SIO Seismometer Data Logger Utility, v1.0")
		self.logger.info("Initialized on " + strftime('%x at %X %Z'))
		self.logger.info("Device type: " + self.config.get("device","model"))
		self.logger.info("Lat: %f" % self.config.getfloat("device","latitude") + "°")
		self.logger.info("Lon: %f" % self.config.getfloat("device","longitude") + "°")
		self.logger.info("Alt: %.1f" % self.config.getfloat("device","altitude")+" meters")

		self.run()

	def stop(self):
		"""
		Stop the daemon
		"""
		self.logger.info("["+ strftime('%X') + "] shutdown requested...")
		
		# 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?\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().
		"""