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svscanpy.py
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svscanpy.py
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#!/usr/bin/env python
# source: https://github.com/patrys/daemontools-ng
from time import time
import dbus
import dbus.service
import gobject
import os
import signal
import sys
import threading
from dbus.mainloop.glib import DBusGMainLoop
class Service(dbus.service.Object):
pid = 0
path = ''
dead = True # do we need to check the pid?
paused = False
lastDied = time() # last death timestamp
respawn = True
interval = 5.0 # avoid infinite restart loops
parent = None
name = ''
okpipe = None
commandpipe = None
def taia_now(self):
now = (long(time()) + 4611686018427387914) << 32
return ''.join(chr(now >> (i * 8) & 0xff) for i in range(11, -1, -1))
def __init__(self, path, parent, name):
super(Service, self).__init__(parent.busName, f'/Services/{name}')
self.name = name
self.path = path
self.parent = parent
self.launch()
def announce(self):
'''
Emulate daemontools for compatibility
'''
dir = os.path.join(self.path, 'supervise')
if not os.path.isdir(dir):
os.mkdir(dir, 0700)
fifo = os.path.join(dir, 'ok')
if not os.path.exists(fifo):
os.mkfifo(fifo, 0600)
if not self.okpipe:
self.okpipe = open(fifo, 'r+')
fifo = os.path.join(dir, 'control')
if not os.path.exists(fifo):
os.mkfifo(fifo, 0600)
if not self.commandpipe:
self.commandpipe = open(fifo, 'r+')
gobject.io_add_watch(self.commandpipe, gobject.IO_IN, self.command)
del fifo
f = open(os.path.join(dir, 'status.new'), 'wb')
f.write(self.taia_now())
for i in range(4): # write pid
if self.dead:
f.write(chr(0))
else:
f.write(chr(self.pid >> (i * 8) & 0xff))
if self.dead: # write paused flag
f.write(chr(0))
else:
f.write(chr(self.paused))
if not self.respawn: # write status
f.write('d')
else:
f.write('u')
f.close()
os.rename(os.path.join(dir, 'status.new'), os.path.join(dir, 'status'))
def command(self, fd, cond):
'''
Emulate daemontools' command fifo
'''
cmd = self.commandpipe.read(1)
if cmd in ('d', 'x'):
print 'die!'
self.setRespawn(False)
if self.paused:
self.kill(signal.SIGCONT)
self.kill(signal.SIGTERM)
elif cmd == 'u':
self.setRespawn(True)
if self.dead:
self.launch()
elif cmd == 'o':
self.setRespawn(False)
if self.dead:
self.launch()
elif cmd == 'a':
self.kill(signal.SIGALRM)
elif cmd == 'h':
self.kill(signal.SIGHUP)
elif cmd == 'k':
self.kill(signal.SIGKILL)
elif cmd == 't':
self.kill(signal.SIGTERM)
elif cmd == 'i':
self.kill(signal.SIGINT)
elif cmd == 'p':
self.kill(signal.SIGSTOP)
elif cmd == 'c':
self.kill(signal.SIGCONT)
return True
@dbus.service.signal(dbus_interface='com.github.patrys.Supervisor.Service', signature='s')
def changed(self, status):
self.announce()
def launch(self):
'''
Launch the service
'''
self.dead = False
runner = os.path.join(self.path, 'run')
if not os.path.exists(runner):
self.lastDied = time()
self.dead = True
self.parent.log(f'unable to start {self.path}: run does not exist')
return
if not os.access(runner, os.X_OK):
self.lastDied = time()
self.dead = True
self.parent.log(f'unable to start {self.path}: run is not executable')
return
self.parent.log(f'starting service: {self.path}')
(self.pid, stdin, stdout, stderr) = gobject.spawn_async(
[runner], working_directory=self.path, flags=gobject.SPAWN_DO_NOT_REAP_CHILD)
if self.pid <= 0:
self.lastDied = time()
self.dead = True
self.parent.log('failed to start process: %s', self.path)
else:
gobject.child_watch_add(self.pid, self.died)
self.changed('up')
def setRespawn(self, respawn):
'''
Change the respawning flag
'''
self.respawn = respawn
self.announce()
@dbus.service.method(dbus_interface='com.github.patrys.Supervisor.Service', in_signature='u')
def kill(self, sig):
'''
Send a signal
'''
if not self.dead:
if sig == signal.SIGSTOP:
self.paused = True
self.changed('paused')
elif sig == signal.SIGCONT:
self.paused = False
self.changed('up')
os.kill(self.pid, sig)
@dbus.service.method(dbus_interface='com.github.patrys.Supervisor.Service', out_signature='uusb')
def status(self):
'''
Return status info
'''
if self.dead:
msg = 'down'
elif self.paused:
msg = 'paused'
else:
msg = 'up'
uptime = time() - self.lastDied
return self.pid, uptime, msg, self.respawn
def died(self, pid, cond, data=None):
'''
Catch a dying child
'''
self.parent.log(f'{self.path} exited with status {cond}')
self.dead = True
self.paused = False
self.changed('down')
if self.respawn:
if time() - self.lastDied > self.interval:
self.launch()
else:
self.parent.log(f'service {self.path} respawning too fast, delaying')
else:
self.parent.log(f'service {self.path} will not be restarted')
self.lastDied = time()
def check(self):
'''
Check service status and respawn it if needed
'''
if self.dead and time() - self.lastDied >= self.interval and self.respawn:
self.parent.log(f'respawning dead service: {self.path}')
self.launch()
class Supervisor(dbus.service.Object):
finished = False
interval = 5
directory = ''
maxServices = 0
services = {}
busName = None
def __init__(self, directory='/service', maxServices=1000):
self.busName = dbus.service.BusName(
'com.github.patrys.Supervisor', bus=dbus.SessionBus())
super(Supervisor, self).__init__(self.busName, '/Manager')
self.directory = directory
self.maxServices = maxServices
gobject.timeout_add(self.interval * 1000, self.run)
self.run()
def log(self, string):
sys.stderr.write(string + '\n')
def scan(self):
'''
Search for services in a specified path and run them
'''
for f in os.listdir(self.directory):
if f[0] == '.':
continue
path = os.path.join(self.directory, f)
path = os.path.realpath(path)
if path in self.services:
continue
if os.path.isdir(path) and not os.path.exists(os.path.join(path, 'down')):
self.startService(path, f)
def startService(self, path, name):
'''
Start a new service and supervise it
'''
path = os.path.realpath(path)
if len(self.services) >= self.maxServices:
self.log(f'unable to start {path}: running too many services')
return
if self.services.has_key(path):
self.log(f'unable to start {path}: already running')
return
if os.path.exists(os.path.join(path, 'run')):
service = Service(path, self, name)
self.services[path] = service
@dbus.service.method(dbus_interface='com.github.patrys.Supervisor', in_signature='s', out_signature='s')
def find(self, path):
path = os.realpath(path)
if self.services.has_key(path):
return '/Services/' . self.services[path].name
else:
return ''
@dbus.service.method(dbus_interface='com.github.patrys.Supervisor', in_signature='', out_signature='as')
def list(self):
return [
f'/Services/{self.services[path].name}'
for path in self.services.keys()
]
def shutdown(self):
'''
Terminate the whole process
'''
self.finished = True
for srv in self.services.values():
srv.setRespawn(False)
srv.kill(signal.SIGTERM)
def run(self):
'''
Idle loop - check for new services and restart dead ones
'''
if self.finished:
return False
self.scan()
for srv in self.services.values():
srv.check()
return True
if __name__ == '__main__':
DBusGMainLoop(set_as_default=True)
s = Supervisor()
try:
gobject.MainLoop().run()
finally:
s.shutdown()