scripts/freecache

#! /usr/bin/python2
# -*- coding: utf-8 -*-
#
__author__='atareao'
__date__ ='$06/11/2011'
#
# control the use of the cache
#
# Copyright (C) 2010 Lorenzo Carbonell
# lorenzo.carbonell.cerezo@gmail.com
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
#
#    
import sys
import os 
import atexit
from signal import SIGTERM
import shlex
import subprocess
import re
import time

def ejecuta(comando):
	args = shlex.split(comando)
	p = subprocess.Popen(args, bufsize=10000, stdout=subprocess.PIPE)
	valor = p.communicate()[0]
	return valor

def s2f(value):
	try:
		val = float(value)
	except:
		val = 0.0
	return val
	
def libera(used, cached):
	ejecuta('sync')
	ejecuta('/sbin/sysctl vm.drop_caches=3')
	total, used_new, cached_new = get_status()
	free = used - used_new
	free_cached = cached -cached_new
	msg = 'Free memory\namount of RAM free %s MB\namount of CACHED free %s MB'%(free,free_cached)
	print msg
	#notification = pynotify.Notification ('Free cache',msg,)
	#notification.show()	

def get_status():
	s = ejecuta('free -m')
	s = re.sub(' +',' ',s).split('\n')[1].split(' ')
	total = s2f(s[1])
	used = s2f(s[2])
	free = s2f(s[3])
	shared = s2f(s[4])
	buffers = s2f(s[5])
	cached = s2f(s[6])
	return total, used, cached

def check():
	total, used, cached = get_status()
	if total > 0:
		used_p = int((used)/total*100.0)
		cached_p = int((cached)/total*100.0)
		print 'Used %s, Cached %s'%(used_p,cached_p)
		if (used_p + cached_p > 90 and cached_p > 15) or (used_p > 95) or (cached_p > 30):
			libera(used,cached)

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)\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()
		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?\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().
		"""
class FreeCache(Daemon):
	def run(self):
		while True:
			time.sleep(10)
			check()

 
if __name__ == "__main__":
	daemon = FreeCache('/tmp/freecache.pid')
	if len(sys.argv) == 2:
		if 'start' == sys.argv[1]:
			daemon.start()
		elif 'stop' == sys.argv[1]:
			daemon.stop()
		elif 'restart' == sys.argv[1]:
			daemon.restart()
		else:
			print "Unknown command"
			sys.exit(2)
		sys.exit(0)
        else:
			print "usage: %s start|stop|restart" % sys.argv[0]
			sys.exit(2)