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
160 @ivar scheduler: A sched.scheduler object, which can be used to register
165 """Constructs a new Mainloop instance.
168 self._signal_wait = []
169 self.scheduler = AsyncoreScheduler(time.time)
171 @utils.SignalHandled([signal.SIGCHLD])
172 @utils.SignalHandled([signal.SIGTERM])
173 def Run(self, signal_handlers=None):
174 """Runs the mainloop.
176 @type signal_handlers: dict
177 @param signal_handlers: signal->L{utils.SignalHandler} passed by decorator
180 assert isinstance(signal_handlers, dict) and \
181 len(signal_handlers) > 0, \
182 "Broken SignalHandled decorator"
184 # Start actual main loop
186 if not self.scheduler.empty():
189 except SchedulerBreakout:
192 asyncore.loop(count=1, use_poll=True)
194 # Check whether a signal was raised
195 for sig in signal_handlers:
196 handler = signal_handlers[sig]
198 self._CallSignalWaiters(sig)
199 running = (sig != signal.SIGTERM)
202 def _CallSignalWaiters(self, signum):
203 """Calls all signal waiters for a certain signal.
206 @param signum: Signal number
209 for owner in self._signal_wait:
210 owner.OnSignal(signum)
212 def RegisterSignal(self, owner):
213 """Registers a receiver for signal notifications
215 The receiver must support a "OnSignal(self, signum)" function.
217 @type owner: instance
218 @param owner: Receiver
221 self._signal_wait.append(owner)
224 def GenericMain(daemon_name, optionparser, dirs, check_fn, exec_fn):
225 """Shared main function for daemons.
227 @type daemon_name: string
228 @param daemon_name: daemon name
229 @type optionparser: optparse.OptionParser
230 @param optionparser: initialized optionparser with daemon-specific options
231 (common -f -d options will be handled by this module)
232 @type dirs: list of strings
233 @param dirs: list of directories that must exist for this daemon to work
234 @type check_fn: function which accepts (options, args)
235 @param check_fn: function that checks start conditions and exits if they're
237 @type exec_fn: function which accepts (options, args)
238 @param exec_fn: function that's executed with the daemon's pid file held, and
239 runs the daemon itself.
242 optionparser.add_option("-f", "--foreground", dest="fork",
243 help="Don't detach from the current terminal",
244 default=True, action="store_false")
245 optionparser.add_option("-d", "--debug", dest="debug",
246 help="Enable some debug messages",
247 default=False, action="store_true")
248 if daemon_name in constants.DAEMONS_PORTS:
249 # for networked daemons we also allow choosing the bind port and address.
250 # by default we use the port provided by utils.GetDaemonPort, and bind to
251 # 0.0.0.0 (which is represented by and empty bind address.
252 port = utils.GetDaemonPort(daemon_name)
253 optionparser.add_option("-p", "--port", dest="port",
254 help="Network port (%s default)." % port,
255 default=port, type="int")
256 optionparser.add_option("-b", "--bind", dest="bind_address",
258 default="", metavar="ADDRESS")
260 if daemon_name in constants.DAEMONS_SSL:
261 default_cert, default_key = constants.DAEMONS_SSL[daemon_name]
262 optionparser.add_option("--no-ssl", dest="ssl",
263 help="Do not secure HTTP protocol with SSL",
264 default=True, action="store_false")
265 optionparser.add_option("-K", "--ssl-key", dest="ssl_key",
267 default=default_key, type="string")
268 optionparser.add_option("-C", "--ssl-cert", dest="ssl_cert",
269 help="SSL certificate",
270 default=default_cert, type="string")
272 multithread = utils.no_fork = daemon_name in constants.MULTITHREADED_DAEMONS
274 options, args = optionparser.parse_args()
276 if hasattr(options, 'ssl') and options.ssl:
277 if not (options.ssl_cert and options.ssl_key):
278 print >> sys.stderr, "Need key and certificate to use ssl"
279 sys.exit(constants.EXIT_FAILURE)
280 for fname in (options.ssl_cert, options.ssl_key):
281 if not os.path.isfile(fname):
282 print >> sys.stderr, "Need ssl file %s to run" % fname
283 sys.exit(constants.EXIT_FAILURE)
285 if check_fn is not None:
286 check_fn(options, args)
288 utils.EnsureDirs(dirs)
292 utils.Daemonize(logfile=constants.DAEMONS_LOGFILES[daemon_name])
294 utils.WritePidFile(daemon_name)
296 utils.SetupLogging(logfile=constants.DAEMONS_LOGFILES[daemon_name],
298 stderr_logging=not options.fork,
299 multithreaded=multithread)
300 logging.info("%s daemon startup" % daemon_name)
301 exec_fn(options, args)
303 utils.RemovePidFile(daemon_name)