"""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):
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.
"""
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
exec_fn(options, args)
finally:
utils.RemovePidFile(daemon_name)
-
projects / ganeti-local / blobdiff