实现代码如下：
# Core modules
importatexit
importos
importsys
importtime
importsignal
classDaemon(object):
"""
A generic daemon class.
Usage: subclass the Daemon class and override the run() method
"""
def __init__(self, pidfile, stdin=os.devnull,
stdout=os.devnull, stderr=os.devnull,
home_dir='.', umask=022, verbose=1):
self.stdin = stdin
self.stdout = stdout
self.stderr = stderr
self.pidfile = pidfile
self.home_dir = home_dir
self.verbose = verbose
self.umask = umask
self.daemon_alive = True
def daemonize(self):
"""
Do the UNIX double-fork magic, see Stevens' "Advanced
Programming in the UNIX Environment" for details (ISBN 0201563177)
"""
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(self.home_dir)
os.setsid()
os.umask(self.umask)
# 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)
if sys.platform != 'darwin': # This block breaks on OS X
# Redirect standard file descriptors
sys.stdout.flush()
sys.stderr.flush()
si = file(self.stdin, 'r')
so = file(self.stdout, 'a+')
if self.stderr:
se = file(self.stderr, 'a+', 0)
else:
se = so
os.dup2(si.fileno(), sys.stdin.fileno())
os.dup2(so.fileno(), sys.stdout.fileno())
os.dup2(se.fileno(), sys.stderr.fileno())
def sigtermhandler(signum, frame):
self.daemon_alive = False
signal.signal(signal.SIGTERM, sigtermhandler)
signal.signal(signal.SIGINT, sigtermhandler)
if self.verbose >= 1:
print "Started"
# Write pidfile
atexit.register(
self.delpid) # Make sure pid file is removed if we quit
pid = str(os.getpid())
file(self.pidfile, 'w+').write("%sn" % pid)
def delpid(self):
os.remove(self.pidfile)
def start(self, *args, **kwargs):
"""
Start the daemon
"""
if self.verbose >= 1:
print "Starting..."
# 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
except SystemExit:
pid = None
if pid:
message = "pidfile %s already exists. Is it already running?n"
sys.stderr.write(message % self.pidfile)
sys.exit(1)
# Start the daemon
self.daemonize()
self.run(*args, **kwargs)
def stop(self):
"""
Stop the daemon
"""
if self.verbose >= 1:
print "Stopping..."
# Get the pid from the pidfile
pid = self.get_pid()
if not pid:
message = "pidfile %s does not exist. Not running?n"
sys.stderr.write(message % self.pidfile)
# Just to be sure. A ValueError might occur if the PID file is
# empty but does actually exist
if os.path.exists(self.pidfile):
os.remove(self.pidfile)
return # Not an error in a restart
# Try killing the daemon process
try:
i = 0
while 1:
os.kill(pid, signal.SIGTERM)
time.sleep(0.1)
i = i + 1
if i % 10 == 0:
os.kill(pid, signal.SIGHUP)
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)
if self.verbose >= 1:
print "Stopped"
def restart(self):
"""
Restart the daemon
"""
self.stop()
self.start()
def get_pid(self):
try:
pf = file(self.pidfile, 'r')
pid = int(pf.read().strip())
pf.close()
except IOError:
pid = None
except SystemExit:
pid = None
return pid
def is_running(self):
pid = self.get_pid()
print(pid)
return pid and os.path.exists('/proc/%d' % pid)
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().
"""
