X-Git-Url: https://code.grnet.gr/git/ganeti-local/blobdiff_plain/577c90a3dbe81bb3cca5c97f19e6877a8bbdc5c9..1e288a2605b4f7584bca1a1f5263e41d6515211c:/lib/daemon.py?ds=inline diff --git a/lib/daemon.py b/lib/daemon.py index e363be3..d357349 100644 --- a/lib/daemon.py +++ b/lib/daemon.py @@ -22,14 +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): @@ -39,99 +162,50 @@ class Mainloop(object): def __init__(self): """Constructs a new Mainloop instance. + @ivar scheduler: A L{sched.scheduler} object, which can be used to register + timed events + """ - self._io_wait = {} - self._io_wait_add = [] - self._io_wait_remove = [] self._signal_wait = [] + self.scheduler = AsyncoreScheduler(time.time) - def Run(self, handle_sigchld=True, handle_sigterm=True, stop_on_empty=False): + @utils.SignalHandled([signal.SIGCHLD]) + @utils.SignalHandled([signal.SIGTERM]) + def Run(self, stop_on_empty=False, signal_handlers=None): """Runs the mainloop. - @type handle_sigchld: bool - @param handle_sigchld: Whether to install handler for SIGCHLD - @type handle_sigterm: bool - @param handle_sigterm: Whether to install handler for SIGTERM @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 """ - poller = select.poll() - - # Setup signal handlers - if handle_sigchld: - sigchld_handler = utils.SignalHandler([signal.SIGCHLD]) - else: - sigchld_handler = None - try: - if handle_sigterm: - sigterm_handler = utils.SignalHandler([signal.SIGTERM]) + 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: + self.scheduler.run() + except SchedulerBreakout: + pass else: - sigterm_handler = None + asyncore.loop(count=1, use_poll=True) - try: - running = True - - # Start actual main loop - while running: - # Entries could be added again afterwards, hence removing first - if self._io_wait_remove: - for fd in self._io_wait_remove: - try: - poller.unregister(fd) - except KeyError: - pass - try: - del self._io_wait[fd] - except KeyError: - pass - self._io_wait_remove = [] - - # Add new entries - if self._io_wait_add: - for (owner, fd, conditions) in self._io_wait_add: - self._io_wait[fd] = owner - poller.register(fd, conditions) - self._io_wait_add = [] - - # Stop if nothing is listening anymore - if stop_on_empty and not (self._io_wait): - break - - # Wait for I/O events - try: - io_events = poller.poll(None) - 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: - owner = self._io_wait.get(evfd, None) - if owner: - owner.OnIO(evfd, evcond) - - # Check whether signal was raised - if sigchld_handler and sigchld_handler.called: - self._CallSignalWaiters(signal.SIGCHLD) - sigchld_handler.Clear() - - if sigterm_handler and sigterm_handler.called: - self._CallSignalWaiters(signal.SIGTERM) - running = False - sigterm_handler.Clear() - finally: - # Restore signal handlers - if sigterm_handler: - sigterm_handler.Reset() - finally: - if sigchld_handler: - sigchld_handler.Reset() + # 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. @@ -141,42 +215,7 @@ class Mainloop(object): """ for owner in self._signal_wait: - owner.OnSignal(signal.SIGCHLD) - - def RegisterIO(self, owner, fd, condition): - """Registers a receiver for I/O notifications - - The receiver must support a "OnIO(self, fd, conditions)" function. - - @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) - - """ - # select.Poller also supports file() like objects, but we don't. - assert isinstance(fd, (int, long)), \ - "Only integers are supported for file descriptors" - - self._io_wait_add.append((owner, fd, condition)) - - def UnregisterIO(self, fd): - """Unregister a file descriptor. - - It'll be unregistered the next time the mainloop checks for it. - - @type fd: int - @param fd: File descriptor - - """ - # select.Poller also supports file() like objects, but we don't. - assert isinstance(fd, (int, long)), \ - "Only integers are supported for file descriptors" - - self._io_wait_remove.append(fd) + owner.OnSignal(signum) def RegisterSignal(self, owner): """Registers a receiver for signal notifications @@ -272,4 +311,3 @@ def GenericMain(daemon_name, optionparser, dirs, check_fn, exec_fn): exec_fn(options, args) finally: utils.RemovePidFile(daemon_name) -