4 # Copyright (C) 2006, 2007, 2008 Google Inc.
6 # This program is free software; you can redistribute it and/or modify
7 # it under the terms of the GNU General Public License as published by
8 # the Free Software Foundation; either version 2 of the License, or
9 # (at your option) any later version.
11 # This program is distributed in the hope that it will be useful, but
12 # WITHOUT ANY WARRANTY; without even the implied warranty of
13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 # General Public License for more details.
16 # You should have received a copy of the GNU General Public License
17 # along with this program; if not, write to the Free Software
18 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
22 """Module with helper classes and functions for daemons"""
35 from ganeti import utils
36 from ganeti import constants
37 from ganeti import errors
40 class SchedulerBreakout(Exception):
41 """Exception used to get out of the scheduler loop
46 def AsyncoreDelayFunction(timeout):
47 """Asyncore-compatible scheduler delay function.
49 This is a delay function for sched that, rather than actually sleeping,
50 executes asyncore events happening in the meantime.
52 After an event has occurred, rather than returning, it raises a
53 SchedulerBreakout exception, which will force the current scheduler.run()
54 invocation to terminate, so that we can also check for signals. The main loop
55 will then call the scheduler run again, which will allow it to actually
56 process any due events.
58 This is needed because scheduler.run() doesn't support a count=..., as
59 asyncore loop, and the scheduler module documents throwing exceptions from
60 inside the delay function as an allowed usage model.
63 asyncore.loop(timeout=timeout, count=1, use_poll=True)
64 raise SchedulerBreakout()
67 class AsyncoreScheduler(sched.scheduler):
68 """Event scheduler integrated with asyncore
71 def __init__(self, timefunc):
72 sched.scheduler.__init__(self, timefunc, AsyncoreDelayFunction)
75 class AsyncUDPSocket(asyncore.dispatcher):
76 """An improved asyncore udp socket.
80 """Constructor for AsyncUDPSocket
83 asyncore.dispatcher.__init__(self)
85 self.create_socket(socket.AF_INET, socket.SOCK_DGRAM)
87 # this method is overriding an asyncore.dispatcher method
88 def handle_connect(self):
89 # Python thinks that the first udp message from a source qualifies as a
90 # "connect" and further ones are part of the same connection. We beg to
91 # differ and treat all messages equally.
94 # this method is overriding an asyncore.dispatcher method
95 def handle_read(self):
98 payload, address = self.recvfrom(constants.MAX_UDP_DATA_SIZE)
99 except socket.error, err:
100 if err.errno == errno.EINTR:
101 # we got a signal while trying to read. no need to do anything,
102 # handle_read will be called again if there is data on the socket.
107 self.handle_datagram(payload, ip, port)
109 # we need to catch any exception here, log it, but proceed, because even
110 # if we failed handling a single request, we still want to continue.
111 logging.error("Unexpected exception", exc_info=True)
113 def handle_datagram(self, payload, ip, port):
114 """Handle an already read udp datagram
117 raise NotImplementedError
119 # this method is overriding an asyncore.dispatcher method
121 # We should check whether we can write to the socket only if we have
122 # something scheduled to be written
123 return bool(self._out_queue)
125 def handle_write(self):
127 if not self._out_queue:
128 logging.error("handle_write called with empty output queue")
130 (ip, port, payload) = self._out_queue[0]
132 self.sendto(payload, 0, (ip, port))
133 except socket.error, err:
134 if err.errno == errno.EINTR:
135 # we got a signal while trying to write. no need to do anything,
136 # handle_write will be called again because we haven't emptied the
137 # _out_queue, and we'll try again
141 self._out_queue.pop(0)
143 # we need to catch any exception here, log it, but proceed, because even
144 # if we failed sending a single datagram we still want to continue.
145 logging.error("Unexpected exception", exc_info=True)
147 def enqueue_send(self, ip, port, payload):
148 """Enqueue a datagram to be sent when possible
151 if len(payload) > constants.MAX_UDP_DATA_SIZE:
152 raise errors.UdpDataSizeError('Packet too big: %s > %s' % (len(payload),
153 constants.MAX_UDP_DATA_SIZE))
154 self._out_queue.append((ip, port, payload))
157 class Mainloop(object):
158 """Generic mainloop for daemons
162 """Constructs a new Mainloop instance.
164 @ivar scheduler: A L{sched.scheduler} object, which can be used to register
168 self._signal_wait = []
169 self.scheduler = AsyncoreScheduler(time.time)
171 @utils.SignalHandled([signal.SIGCHLD])
172 @utils.SignalHandled([signal.SIGTERM])
173 def Run(self, stop_on_empty=False, signal_handlers=None):
174 """Runs the mainloop.
176 @type stop_on_empty: bool
177 @param stop_on_empty: Whether to stop mainloop once all I/O waiters
179 @type signal_handlers: dict
180 @param signal_handlers: signal->L{utils.SignalHandler} passed by decorator
183 assert isinstance(signal_handlers, dict) and \
184 len(signal_handlers) > 0, \
185 "Broken SignalHandled decorator"
187 # Start actual main loop
189 # Stop if nothing is listening anymore
190 if stop_on_empty and not (self._io_wait):
193 if not self.scheduler.empty():
196 except SchedulerBreakout:
199 asyncore.loop(count=1, use_poll=True)
201 # Check whether a signal was raised
202 for sig in signal_handlers:
203 handler = signal_handlers[sig]
205 self._CallSignalWaiters(sig)
206 running = (sig != signal.SIGTERM)
209 def _CallSignalWaiters(self, signum):
210 """Calls all signal waiters for a certain signal.
213 @param signum: Signal number
216 for owner in self._signal_wait:
217 owner.OnSignal(signum)
219 def RegisterSignal(self, owner):
220 """Registers a receiver for signal notifications
222 The receiver must support a "OnSignal(self, signum)" function.
224 @type owner: instance
225 @param owner: Receiver
228 self._signal_wait.append(owner)
231 def GenericMain(daemon_name, optionparser, dirs, check_fn, exec_fn):
232 """Shared main function for daemons.
234 @type daemon_name: string
235 @param daemon_name: daemon name
236 @type optionparser: L{optparse.OptionParser}
237 @param optionparser: initialized optionparser with daemon-specific options
238 (common -f -d options will be handled by this module)
239 @type options: object @param options: OptionParser result, should contain at
240 least the fork and the debug options
241 @type dirs: list of strings
242 @param dirs: list of directories that must exist for this daemon to work
243 @type check_fn: function which accepts (options, args)
244 @param check_fn: function that checks start conditions and exits if they're
246 @type exec_fn: function which accepts (options, args)
247 @param exec_fn: function that's executed with the daemon's pid file held, and
248 runs the daemon itself.
251 optionparser.add_option("-f", "--foreground", dest="fork",
252 help="Don't detach from the current terminal",
253 default=True, action="store_false")
254 optionparser.add_option("-d", "--debug", dest="debug",
255 help="Enable some debug messages",
256 default=False, action="store_true")
257 if daemon_name in constants.DAEMONS_PORTS:
258 # for networked daemons we also allow choosing the bind port and address.
259 # by default we use the port provided by utils.GetDaemonPort, and bind to
260 # 0.0.0.0 (which is represented by and empty bind address.
261 port = utils.GetDaemonPort(daemon_name)
262 optionparser.add_option("-p", "--port", dest="port",
263 help="Network port (%s default)." % port,
264 default=port, type="int")
265 optionparser.add_option("-b", "--bind", dest="bind_address",
267 default="", metavar="ADDRESS")
269 if daemon_name in constants.DAEMONS_SSL:
270 default_cert, default_key = constants.DAEMONS_SSL[daemon_name]
271 optionparser.add_option("--no-ssl", dest="ssl",
272 help="Do not secure HTTP protocol with SSL",
273 default=True, action="store_false")
274 optionparser.add_option("-K", "--ssl-key", dest="ssl_key",
276 default=default_key, type="string")
277 optionparser.add_option("-C", "--ssl-cert", dest="ssl_cert",
278 help="SSL certificate",
279 default=default_cert, type="string")
281 multithread = utils.no_fork = daemon_name in constants.MULTITHREADED_DAEMONS
283 options, args = optionparser.parse_args()
285 if hasattr(options, 'ssl') and options.ssl:
286 if not (options.ssl_cert and options.ssl_key):
287 print >> sys.stderr, "Need key and certificate to use ssl"
288 sys.exit(constants.EXIT_FAILURE)
289 for fname in (options.ssl_cert, options.ssl_key):
290 if not os.path.isfile(fname):
291 print >> sys.stderr, "Need ssl file %s to run" % fname
292 sys.exit(constants.EXIT_FAILURE)
294 if check_fn is not None:
295 check_fn(options, args)
297 utils.EnsureDirs(dirs)
301 utils.Daemonize(logfile=constants.DAEMONS_LOGFILES[daemon_name])
303 utils.WritePidFile(daemon_name)
305 utils.SetupLogging(logfile=constants.DAEMONS_LOGFILES[daemon_name],
307 stderr_logging=not options.fork,
308 multithreaded=multithread)
309 logging.info("%s daemon startup" % daemon_name)
310 exec_fn(options, args)
312 utils.RemovePidFile(daemon_name)