root / lib / daemon.py @ b14b975f
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# Copyright (C) 2006, 2007, 2008 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Module with helper classes and functions for daemons"""
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import select |
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import signal |
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import errno |
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from ganeti import utils |
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class Mainloop(object): |
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"""Generic mainloop for daemons
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"""
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def __init__(self): |
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"""Constructs a new Mainloop instance.
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"""
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self._io_wait = {}
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self._io_wait_add = []
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self._io_wait_remove = []
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self._signal_wait = []
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def Run(self, handle_sigchld=True, handle_sigterm=True, stop_on_empty=False): |
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"""Runs the mainloop.
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@type handle_sigchld: bool
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@param handle_sigchld: Whether to install handler for SIGCHLD
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@type handle_sigterm: bool
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@param handle_sigterm: Whether to install handler for SIGTERM
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@type stop_on_empty: bool
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@param stop_on_empty: Whether to stop mainloop once all I/O waiters
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unregistered
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"""
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poller = select.poll() |
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# Setup signal handlers
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if handle_sigchld:
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sigchld_handler = utils.SignalHandler([signal.SIGCHLD]) |
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else:
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sigchld_handler = None
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try:
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if handle_sigterm:
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sigterm_handler = utils.SignalHandler([signal.SIGTERM]) |
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else:
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sigterm_handler = None
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try:
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running = True
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# Start actual main loop
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while running:
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# Entries could be added again afterwards, hence removing first
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if self._io_wait_remove: |
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for fd in self._io_wait_remove: |
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try:
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poller.unregister(fd) |
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except KeyError: |
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pass
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try:
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del self._io_wait[fd] |
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except KeyError: |
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pass
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self._io_wait_remove = []
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# Add new entries
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if self._io_wait_add: |
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for (owner, fd, conditions) in self._io_wait_add: |
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self._io_wait[fd] = owner
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poller.register(fd, conditions) |
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self._io_wait_add = []
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# Stop if nothing is listening anymore
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if stop_on_empty and not self._io_wait: |
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break
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# Wait for I/O events
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try:
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io_events = poller.poll() |
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except select.error, err:
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# EINTR can happen when signals are sent
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if err.args and err.args[0] in (errno.EINTR,): |
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io_events = None
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else:
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raise
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if io_events:
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# Check for I/O events
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for (evfd, evcond) in io_events: |
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owner = self._io_wait.get(evfd, None) |
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if owner:
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owner.OnIO(evfd, evcond) |
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# Check whether signal was raised
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if sigchld_handler and sigchld_handler.called: |
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self._CallSignalWaiters(signal.SIGCHLD)
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sigchld_handler.Clear() |
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if sigterm_handler and sigterm_handler.called: |
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self._CallSignalWaiters(signal.SIGTERM)
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running = False
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sigterm_handler.Clear() |
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finally:
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# Restore signal handlers
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if sigterm_handler:
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sigterm_handler.Reset() |
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finally:
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if sigchld_handler:
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sigchld_handler.Reset() |
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def _CallSignalWaiters(self, signum): |
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"""Calls all signal waiters for a certain signal.
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@type signum: int
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@param signum: Signal number
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"""
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for owner in self._signal_wait: |
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owner.OnSignal(signal.SIGCHLD) |
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def RegisterIO(self, owner, fd, condition): |
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"""Registers a receiver for I/O notifications
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The receiver must support a "OnIO(self, fd, conditions)" function.
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@type owner: instance
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@param owner: Receiver
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@type fd: int
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@param fd: File descriptor
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@type condition: int
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@param condition: ORed field of conditions to be notified
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(see select module)
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"""
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# select.Poller also supports file() like objects, but we don't.
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assert isinstance(fd, (int, long)), \ |
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"Only integers are supported for file descriptors"
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self._io_wait_add.append((owner, fd, condition))
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def UnregisterIO(self, fd): |
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"""Unregister a file descriptor.
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It'll be unregistered the next time the mainloop checks for it.
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@type fd: int
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@param fd: File descriptor
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"""
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# select.Poller also supports file() like objects, but we don't.
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assert isinstance(fd, (int, long)), \ |
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"Only integers are supported for file descriptors"
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self._io_wait_remove.append(fd)
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def RegisterSignal(self, owner): |
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"""Registers a receiver for signal notifications
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The receiver must support a "OnSignal(self, signum)" function.
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@type owner: instance
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@param owner: Receiver
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"""
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self._signal_wait.append(owner)
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