X-Git-Url: https://code.grnet.gr/git/ganeti-local/blobdiff_plain/07fc52893578b0bc530a2f10efaa3cfa5a9e4039..008b92fa2d89e7678f5d11fe9d4e4d8004e776ee:/lib/daemon.py diff --git a/lib/daemon.py b/lib/daemon.py index 0f6f540..d357349 100644 --- a/lib/daemon.py +++ b/lib/daemon.py @@ -22,11 +22,137 @@ """Module with helper classes and functions for daemons""" +import asyncore +import os import select import signal import errno +import logging +import sched +import time +import socket +import sys from ganeti import utils +from ganeti import constants +from ganeti import errors + + +class SchedulerBreakout(Exception): + """Exception used to get out of the scheduler loop + + """ + + +def AsyncoreDelayFunction(timeout): + """Asyncore-compatible scheduler delay function. + + This is a delay function for sched that, rather than actually sleeping, + executes asyncore events happening in the meantime. + + After an event has occurred, rather than returning, it raises a + SchedulerBreakout exception, which will force the current scheduler.run() + invocation to terminate, so that we can also check for signals. The main loop + will then call the scheduler run again, which will allow it to actually + process any due events. + + This is needed because scheduler.run() doesn't support a count=..., as + asyncore loop, and the scheduler module documents throwing exceptions from + inside the delay function as an allowed usage model. + + """ + asyncore.loop(timeout=timeout, count=1, use_poll=True) + raise SchedulerBreakout() + + +class AsyncoreScheduler(sched.scheduler): + """Event scheduler integrated with asyncore + + """ + def __init__(self, timefunc): + sched.scheduler.__init__(self, timefunc, AsyncoreDelayFunction) + + +class AsyncUDPSocket(asyncore.dispatcher): + """An improved asyncore udp socket. + + """ + def __init__(self): + """Constructor for AsyncUDPSocket + + """ + asyncore.dispatcher.__init__(self) + self._out_queue = [] + self.create_socket(socket.AF_INET, socket.SOCK_DGRAM) + + # this method is overriding an asyncore.dispatcher method + def handle_connect(self): + # Python thinks that the first udp message from a source qualifies as a + # "connect" and further ones are part of the same connection. We beg to + # differ and treat all messages equally. + pass + + # this method is overriding an asyncore.dispatcher method + def handle_read(self): + try: + try: + payload, address = self.recvfrom(constants.MAX_UDP_DATA_SIZE) + except socket.error, err: + if err.errno == errno.EINTR: + # we got a signal while trying to read. no need to do anything, + # handle_read will be called again if there is data on the socket. + return + else: + raise + ip, port = address + self.handle_datagram(payload, ip, port) + except: + # we need to catch any exception here, log it, but proceed, because even + # if we failed handling a single request, we still want to continue. + logging.error("Unexpected exception", exc_info=True) + + def handle_datagram(self, payload, ip, port): + """Handle an already read udp datagram + + """ + raise NotImplementedError + + # this method is overriding an asyncore.dispatcher method + def writable(self): + # We should check whether we can write to the socket only if we have + # something scheduled to be written + return bool(self._out_queue) + + def handle_write(self): + try: + if not self._out_queue: + logging.error("handle_write called with empty output queue") + return + (ip, port, payload) = self._out_queue[0] + try: + self.sendto(payload, 0, (ip, port)) + except socket.error, err: + if err.errno == errno.EINTR: + # we got a signal while trying to write. no need to do anything, + # handle_write will be called again because we haven't emptied the + # _out_queue, and we'll try again + return + else: + raise + self._out_queue.pop(0) + except: + # we need to catch any exception here, log it, but proceed, because even + # if we failed sending a single datagram we still want to continue. + logging.error("Unexpected exception", exc_info=True) + + def enqueue_send(self, ip, port, payload): + """Enqueue a datagram to be sent when possible + + """ + if len(payload) > constants.MAX_UDP_DATA_SIZE: + raise errors.UdpDataSizeError('Packet too big: %s > %s' % (len(payload), + constants.MAX_UDP_DATA_SIZE)) + self._out_queue.append((ip, port, payload)) class Mainloop(object): @@ -34,59 +160,62 @@ class Mainloop(object): """ def __init__(self): - self._io_wait = [] + """Constructs a new Mainloop instance. + + @ivar scheduler: A L{sched.scheduler} object, which can be used to register + timed events + + """ self._signal_wait = [] - self.sigchld_handler = None + self.scheduler = AsyncoreScheduler(time.time) - def Run(self): - # TODO: Does not yet support adding new event sources while running - poller = select.poll() - for (owner, fd, conditions) in self._io_wait: - poller.register(fd, conditions) + @utils.SignalHandled([signal.SIGCHLD]) + @utils.SignalHandled([signal.SIGTERM]) + def Run(self, stop_on_empty=False, signal_handlers=None): + """Runs the mainloop. - self.sigchld_handler = utils.SignalHandler([signal.SIGCHLD]) - try: - while True: + @type stop_on_empty: bool + @param stop_on_empty: Whether to stop mainloop once all I/O waiters + unregistered + @type signal_handlers: dict + @param signal_handlers: signal->L{utils.SignalHandler} passed by decorator + + """ + assert isinstance(signal_handlers, dict) and \ + len(signal_handlers) > 0, \ + "Broken SignalHandled decorator" + running = True + # Start actual main loop + while running: + # Stop if nothing is listening anymore + if stop_on_empty and not (self._io_wait): + break + + if not self.scheduler.empty(): try: - io_events = poller.poll(1000) - except select.error, err: - # EINTR can happen when signals are sent - if err.args and err.args[0] in (errno.EINTR,): - io_events = None - else: - raise - - if io_events: - # Check for I/O events - for (evfd, evcond) in io_events: - for (owner, fd, conditions) in self._io_wait: - if fd == evfd and evcond & conditions: - owner.OnIO(fd, evcond) - - # Check whether signal was raised - if self.sigchld_handler.called: - for owner in self._signal_wait: - owner.OnSignal(signal.SIGCHLD) - self.sigchld_handler.Clear() - finally: - self.sigchld_handler.Reset() - self.sigchld_handler = None - - def RegisterIO(self, owner, fd, condition): - """Registers a receiver for I/O notifications - - The receiver must support a "OnIO(self, fd, conditions)" function. + self.scheduler.run() + except SchedulerBreakout: + pass + else: + asyncore.loop(count=1, use_poll=True) - @type owner: instance - @param owner: Receiver - @type fd: int - @param fd: File descriptor - @type condition: int - @param condition: ORed field of conditions to be notified - (see select module) + # Check whether a signal was raised + for sig in signal_handlers: + handler = signal_handlers[sig] + if handler.called: + self._CallSignalWaiters(sig) + running = (sig != signal.SIGTERM) + handler.Clear() + + def _CallSignalWaiters(self, signum): + """Calls all signal waiters for a certain signal. + + @type signum: int + @param signum: Signal number """ - self._io_wait.append((owner, fd, condition)) + for owner in self._signal_wait: + owner.OnSignal(signum) def RegisterSignal(self, owner): """Registers a receiver for signal notifications @@ -98,3 +227,87 @@ class Mainloop(object): """ self._signal_wait.append(owner) + + +def GenericMain(daemon_name, optionparser, dirs, check_fn, exec_fn): + """Shared main function for daemons. + + @type daemon_name: string + @param daemon_name: daemon name + @type optionparser: L{optparse.OptionParser} + @param optionparser: initialized optionparser with daemon-specific options + (common -f -d options will be handled by this module) + @type options: object @param options: OptionParser result, should contain at + least the fork and the debug options + @type dirs: list of strings + @param dirs: list of directories that must exist for this daemon to work + @type check_fn: function which accepts (options, args) + @param check_fn: function that checks start conditions and exits if they're + not met + @type exec_fn: function which accepts (options, args) + @param exec_fn: function that's executed with the daemon's pid file held, and + runs the daemon itself. + + """ + optionparser.add_option("-f", "--foreground", dest="fork", + help="Don't detach from the current terminal", + default=True, action="store_false") + optionparser.add_option("-d", "--debug", dest="debug", + help="Enable some debug messages", + default=False, action="store_true") + if daemon_name in constants.DAEMONS_PORTS: + # for networked daemons we also allow choosing the bind port and address. + # by default we use the port provided by utils.GetDaemonPort, and bind to + # 0.0.0.0 (which is represented by and empty bind address. + port = utils.GetDaemonPort(daemon_name) + optionparser.add_option("-p", "--port", dest="port", + help="Network port (%s default)." % port, + default=port, type="int") + optionparser.add_option("-b", "--bind", dest="bind_address", + help="Bind address", + default="", metavar="ADDRESS") + + if daemon_name in constants.DAEMONS_SSL: + default_cert, default_key = constants.DAEMONS_SSL[daemon_name] + optionparser.add_option("--no-ssl", dest="ssl", + help="Do not secure HTTP protocol with SSL", + default=True, action="store_false") + optionparser.add_option("-K", "--ssl-key", dest="ssl_key", + help="SSL key", + default=default_key, type="string") + optionparser.add_option("-C", "--ssl-cert", dest="ssl_cert", + help="SSL certificate", + default=default_cert, type="string") + + multithread = utils.no_fork = daemon_name in constants.MULTITHREADED_DAEMONS + + options, args = optionparser.parse_args() + + if hasattr(options, 'ssl') and options.ssl: + if not (options.ssl_cert and options.ssl_key): + print >> sys.stderr, "Need key and certificate to use ssl" + sys.exit(constants.EXIT_FAILURE) + for fname in (options.ssl_cert, options.ssl_key): + if not os.path.isfile(fname): + print >> sys.stderr, "Need ssl file %s to run" % fname + sys.exit(constants.EXIT_FAILURE) + + if check_fn is not None: + check_fn(options, args) + + utils.EnsureDirs(dirs) + + if options.fork: + utils.CloseFDs() + utils.Daemonize(logfile=constants.DAEMONS_LOGFILES[daemon_name]) + + utils.WritePidFile(daemon_name) + try: + utils.SetupLogging(logfile=constants.DAEMONS_LOGFILES[daemon_name], + debug=options.debug, + stderr_logging=not options.fork, + multithreaded=multithread) + logging.info("%s daemon startup" % daemon_name) + exec_fn(options, args) + finally: + utils.RemovePidFile(daemon_name)