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"""A daemon mix-in class.
:copyright: 2000-2008 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
:license: General Public License version 2 - http://www.gnu.org/licenses
"""
__docformat__ = "restructuredtext en"
import os, signal, sys, time
from logilab.common.logger import make_logger, LOG_ALERT, LOG_NOTICE
class DaemonMixIn:
"""Mixin to make a daemon from watchers/queriers.
"""
def __init__(self, configmod) :
self.delay = configmod.DELAY
self.name = str(self.__class__).split('.')[-1]
self._pid_file = os.path.join('/tmp', '%s.pid'%self.name)
if os.path.exists(self._pid_file):
raise Exception('''Another instance of %s must be running.
If it i not the case, remove the file %s''' % (self.name, self._pid_file))
self._alive = 1
self._sleeping = 0
treshold = configmod.LOG_TRESHOLD
if configmod.NODETACH:
configmod.log = make_logger('print', treshold, self.name).log
else:
configmod.log = make_logger('syslog', treshold, self.name).log
self.config = configmod
def _daemonize(self):
if not self.config.NODETACH:
# fork so the parent can exist
if (os.fork()):
return -1
# deconnect from tty and create a new session
os.setsid()
# fork again so the parent, (the session group leader), can exit.
# as a non-session group leader, we can never regain a controlling
# terminal.
if (os.fork()):
return -1
# move to the root to avoit mount pb
os.chdir('/')
# set paranoid umask
os.umask(077)
# write pid in a file
f = open(self._pid_file, 'w')
f.write(str(os.getpid()))
f.close()
# close standard descriptors
sys.stdin.close()
sys.stdout.close()
sys.stderr.close()
# put signal handler
signal.signal(signal.SIGTERM, self.signal_handler)
signal.signal(signal.SIGHUP, self.signal_handler)
def run(self):
""" optionaly go in daemon mode and
do what concrete classe has to do and pauses for delay between runs
If self.delay is negative, do a pause before starting
"""
if self._daemonize() == -1:
return
self.config.log(LOG_NOTICE, '%s instance started' % self.name)
if self.delay < 0:
self.delay = -self.delay
time.sleep(self.delay)
while 1:
try:
self._run()
except Exception, e:
# display for info, sleep, and hope the problem will be solved
# later.
self.config.log(LOG_ALERT, 'Internal error: %s'%(e))
if not self._alive:
break
try:
self._sleeping = 1
time.sleep(self.delay)
self._sleeping = 0
except SystemExit:
break
self.config.log(LOG_NOTICE, '%s instance exited'%self.name)
# remove pid file
os.remove(self._pid_file)
def signal_handler(self, sig_num, stack_frame):
if sig_num == signal.SIGTERM:
if self._sleeping:
# we are sleeping so we can exit without fear
self.config.log(LOG_NOTICE, 'exit on SIGTERM')
sys.exit(0)
else:
self.config.log(LOG_NOTICE, 'exit on SIGTERM (on next turn)')
self._alive = 0
elif sig_num == signal.SIGHUP:
self.config.log(LOG_NOTICE, 'reloading configuration on SIGHUP')
reload(self.config)
def _run(self):
"""should be overidden in the mixed class"""
raise NotImplementedError()
## command line utilities ######################################################
L_OPTIONS = ["help", "log=", "delay=", 'no-detach']
S_OPTIONS = 'hl:d:n'
def print_help(modconfig):
print """ --help or -h
displays this message
--log <log_level>
log treshold (7 record everything, 0 record only emergency.)
Defaults to %s
--delay <delay>
the number of seconds between two runs.
Defaults to %s""" % (modconfig.LOG_TRESHOLD, modconfig.DELAY)
def handle_option(modconfig, opt_name, opt_value, help_meth):
if opt_name in ('-h','--help'):
help_meth()
sys.exit(0)
elif opt_name in ('-l','--log'):
modconfig.LOG_TRESHOLD = int(opt_value)
elif opt_name in ('-d', '--delay'):
modconfig.DELAY = int(opt_value)
elif opt_name in ('-n', '--no-detach'):
modconfig.NODETACH = 1
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