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Deamon.py
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'''
Created on Sep 30, 2010
@author: ikons
'''
#!/usr/bin/env python
import sys, os, time, atexit, logging.handlers
from signal import SIGTERM
#import shutil, fileinput
import Utils
class Daemon:
"""
A generic daemon class.
Usage: subclass the Daemon class and override the run() method
"""
def __init__(self, pidfile, properties_file, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
self.stdin = stdin
self.stdout = stdout
self.stderr = stderr
self.pidfile = pidfile
self.properties_file = properties_file
## Read properties from file
self.utils = Utils.Utils(properties_file)
## Make log directory
self.utils.mkdir_p(self.utils.install_dir+'/'+self.utils.logs_folder_name)
## Install stdout
self.stdout = self.utils.install_dir+"/"+self.utils.logs_folder_name+"/Coordinator.out"
## Install stderr
self.stderr = self.utils.install_dir+"/"+self.utils.logs_folder_name+"/Coordinator.err"
## Install logger
LOG_FILENAME = self.utils.install_dir+'/'+self.utils.logs_folder_name+'/Coordinator.log'
self.my_logger = logging.getLogger('Deamon')
self.my_logger.setLevel(self.utils.logging_level)
handler = logging.handlers.RotatingFileHandler(
LOG_FILENAME, maxBytes=2*1024*1024, backupCount=5)
formatter = logging.Formatter("%(asctime)s - %(levelname)s - %(name)s - %(message)s")
handler.setFormatter(formatter)
self.my_logger.addHandler(handler)
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.chdir(self.utils.install_dir)
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)
# uncomment the above line to redirect stderr
os.dup2(si.fileno(), sys.stdin.fileno())
os.dup2(so.fileno(), sys.stdout.fileno())
os.dup2(se.fileno(), sys.stderr.fileno())
# uncomment the above line to redirect stderr
# 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?
"
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().
"""
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