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@thebookworm101
Forked from Jd007/gist:5573672
Created July 5, 2013 19:30
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import sys, os, time, atexit
from signal import SIGTERM
class Daemon:
'''
Base Daemon class that takes care of the start, stop, and forking of the processes.
Used to daemonize any Python script.
'''
def __init__(self, pidfile, worker_id, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
self.pidfile = pidfile
self.worker_id = worker_id
self.stdin = stdin
self.stdout = stdout
self.stderr = stderr
self.init_time = int(time.time())
self.successful_job_count = 0
self.failed_job_count = 0
self.avg_job_time = 0
def daemonize(self):
'''
Double-forks the process to daemonize the script.
'''
try:
pid = os.fork()
if pid > 0:
# Exit from 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)
# 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 the PID file
atexit.register(self.delpid)
pid = str(os.getpid())
file(self.pidfile, 'w+').write("%s\n" % pid)
def delpid(self):
# Removes the PID file
os.remove(self.pidfile)
def start(self):
'''
Start the daemon.
'''
# Check for a PID file to see if the Daemon is already running
try:
pf = file(self.pidfile, 'r')
pid = int(pf.read().strip())
pf.close()
except IOError:
pid = None
if pid:
message = "PID file %s already exist. Daemon already running?\n"
sys.stderr.write(message % self.pidfile)
sys.exit(1)
# No PID file, start the daemon
self.daemonize()
self.run()
def stop(self):
'''
Stop the daemon.
'''
# Get the PID from the PID file
try:
pf = file(self.pidfile, 'r')
pid = int(pf.read().strip())
pf.close()
except IOError:
pid = None
if not pid:
message = "PID file %s does not exist. Daemon not running?\n"
sys.stderr.write(message % self.pidfile)
return # not an error in a restart
# Try to kill 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):
'''
The script to execute by the daemon after it starts.
'''
pass
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