From 6da8d09846db4d2eed01e488bc6a6f5ba48b959f Mon Sep 17 00:00:00 2001 From: Kali Kaneko Date: Mon, 12 Aug 2013 13:25:44 +0200 Subject: move everything into bitmask namespace --- src/leap/bitmask/platform_init/locks.py | 405 ++++++++++++++++++++++++++++++++ 1 file changed, 405 insertions(+) create mode 100644 src/leap/bitmask/platform_init/locks.py (limited to 'src/leap/bitmask/platform_init/locks.py') diff --git a/src/leap/bitmask/platform_init/locks.py b/src/leap/bitmask/platform_init/locks.py new file mode 100644 index 00000000..39b18648 --- /dev/null +++ b/src/leap/bitmask/platform_init/locks.py @@ -0,0 +1,405 @@ +# -*- coding: utf-8 -*- +# locks.py +# Copyright (C) 2013 LEAP +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . +""" +Utilities for handling multi-platform file locking mechanisms +""" +import logging +import errno +import os +import platform + +from leap.common.events import signal as signal_event +from leap.common.events import events_pb2 as proto +from leap import platform_init + +if platform_init.IS_UNIX: + from fcntl import flock, LOCK_EX, LOCK_NB +else: # WINDOWS + import datetime + import glob + import shutil + import time + + from tempfile import gettempdir + + from leap.util import get_modification_ts, update_modification_ts + +logger = logging.getLogger(__name__) + +if platform_init.IS_UNIX: + + class UnixLock(object): + """ + Uses flock to get an exclusive lock over a file. + See man 2 flock + """ + + def __init__(self, path): + """ + iniializes t he UnixLock with the path of the + desired lockfile + """ + + self._fd = None + self.path = path + + def get_lock(self): + """ + Tries to get a lock, and writes the running pid there if successful + """ + gotit, pid = self._get_lock_and_pid() + return gotit + + def get_pid(self): + """ + Returns the pid of the locking process + """ + gotit, pid = self._get_lock_and_pid() + return pid + + def _get_lock(self): + """ + Tries to get a lock, returning True if successful + + :rtype: bool + """ + self._fd = os.open(self.path, os.O_CREAT | os.O_RDWR) + + try: + flock(self._fd, LOCK_EX | LOCK_NB) + except IOError as exc: + # could not get the lock + #import ipdb; ipdb.set_trace() + + if exc.args[0] in (errno.EDEADLK, errno.EAGAIN): + # errno 11 or 35 + # Resource temporarily unavailable + return False + else: + raise + return True + + @property + def locked_by_us(self): + """ + Returns True if the pid in the pidfile + is ours. + + :rtype: bool + """ + gotit, pid = self._get_lock_and_pid() + return pid == os.getpid() + + def _get_lock_and_pid(self): + """ + Tries to get a lock over the file. + Returns (locked, pid) tuple. + + :rtype: tuple + """ + + if self._get_lock(): + self._write_to_pidfile() + return True, None + + return False, self._read_from_pidfile() + + def _read_from_pidfile(self): + """ + Tries to read pid from the pidfile, + returns False if no content found. + """ + + pidfile = os.read( + self._fd, 16) + if not pidfile: + return False + + try: + return int(pidfile.strip()) + except Exception as exc: + exc.args += (pidfile, self.lock_file) + raise + + def _write_to_pidfile(self): + """ + Writes the pid of the running process + to the pidfile + """ + fd = self._fd + os.ftruncate(fd, 0) + os.write(fd, '%d\n' % os.getpid()) + os.fsync(fd) + + +if platform_init.IS_WIN: + + # Time to wait (in secs) before assuming a raise window signal has not been + # ack-ed. + + RAISE_WINDOW_TIMEOUT = 2 + + # How many steps to do while checking lockfile ts update. + + RAISE_WINDOW_WAIT_STEPS = 10 + + def _release_lock(name): + """ + Tries to remove a folder path. + + :param name: folder lock to remove + :type name: str + """ + try: + shutil.rmtree(name) + return True + except WindowsError as exc: + if exc.errno in (errno.EPIPE, errno.ENOENT, + errno.ESRCH, errno.EACCES): + logger.warning( + 'exception while trying to remove the lockfile dir') + logger.warning('errno %s: %s' % (exc.errno, exc.args[1])) + # path does not exist + return False + else: + logger.debug('errno = %s' % (exc.errno,)) + # we did not foresee this error, better add it explicitely + raise + + class WindowsLock(object): + """ + Creates a lock based on the atomic nature of mkdir on Windows + system calls. + """ + LOCKBASE = os.path.join(gettempdir(), "leap-client-lock") + + def __init__(self): + """ + Initializes the lock. + Sets the lock name to basename plus the process pid. + """ + self._fd = None + pid = os.getpid() + self.name = "%s-%s" % (self.LOCKBASE, pid) + self.pid = pid + + def get_lock(self): + """ + Tries to get a lock, and writes the running pid there if successful + """ + gotit = self._get_lock() + return gotit + + def _get_lock(self): + """ + Tries to write to a file with the current pid as part of the name + """ + try: + self._fd = os.makedirs(self.name) + except OSError as exc: + # could not create the dir + if exc.args[0] == 183: + logger.debug('cannot create dir') + # cannot create dir with existing name + return False + else: + raise + return self._is_one_pidfile()[0] + + def _is_one_pidfile(self): + """ + Returns True, pid if there is only one pidfile with the expected + base path + + :rtype: tuple + """ + pidfiles = glob.glob(self.LOCKBASE + '-*') + if len(pidfiles) == 1: + pid = pidfiles[0].split('-')[-1] + return True, int(pid) + else: + return False, None + + def get_pid(self): + """ + Returns the pid of the locking process. + + :rtype: int + """ + # XXX assert there is only one? + _, pid = self._is_one_pidfile() + return pid + + def get_locking_path(self): + """ + Returns the pid path of the locking process. + + :rtype: str + """ + pid = self.get_pid() + if pid: + return "%s-%s" % (self.LOCKBASE, pid) + + def release_lock(self, name=None): + """ + Releases the pidfile dir for this process, by removing it. + """ + if not name: + name = self.name + _release_lock(name) + + @classmethod + def release_all_locks(self): + """ + Releases all locks. Used for clean shutdown. + """ + for lockdir in glob.glob("%s-%s" % (self.LOCKBASE, '*')): + _release_lock(lockdir) + + @property + def locked_by_us(self): + """ + Returns True if the pid in the pidfile + is ours. + + :rtype: bool + """ + _, pid = self._is_one_pidfile() + return pid == self.pid + + def update_ts(self): + """ + Updates the timestamp of the lock. + """ + if self.locked_by_us: + update_modification_ts(self.name) + + def write_port(self, port): + """ + Writes the port for windows control to the pidfile folder + Returns True if successful. + + :rtype: bool + """ + if not self.locked_by_us: + logger.warning("Tried to write control port to a " + "non-unique pidfile folder") + return False + port_file = os.path.join(self.name, "port") + with open(port_file, 'w') as f: + f.write("%s" % port) + return True + + def get_control_port(self): + """ + Reads control port of the main instance from the port file + in the pidfile dir + + :rtype: int + """ + pid = self.get_pid() + port_file = os.path.join(self.LOCKBASE + "-%s" % pid, "port") + port = None + try: + with open(port_file) as f: + port_str = f.read() + port = int(port_str.strip()) + except IOError as exc: + if exc.errno == errno.ENOENT: + logger.error("Tried to read port from non-existent file") + else: + # we did not know explicitely about this error + raise + return port + + def raise_window_ack(): + """ + This function is called from the windows callback that is registered + with the raise_window event. It just updates the modification time + of the lock file so we can signal an ack to the instance that tried + to raise the window. + """ + lock = WindowsLock() + lock.update_ts() + + +def we_are_the_one_and_only(): + """ + Returns True if we are the only instance running, False otherwise. + If we came later, send a raise signal to the main instance of the + application. + + Under windows we are not using flock magic, so we wait during + RAISE_WINDOW_TIMEOUT time, if not ack is + received, we assume it was a stalled lock, so we remove it and continue + with initialization. + + :rtype: bool + """ + _sys = platform.system() + + if _sys in ("Linux", "Darwin"): + locker = UnixLock('/tmp/leap-client.lock') + locker.get_lock() + we_are_the_one = locker.locked_by_us + if not we_are_the_one: + signal_event(proto.RAISE_WINDOW) + return we_are_the_one + + elif _sys == "Windows": + locker = WindowsLock() + locker.get_lock() + we_are_the_one = locker.locked_by_us + + if not we_are_the_one: + locker.release_lock() + lock_path = locker.get_locking_path() + ts = get_modification_ts(lock_path) + + nowfun = datetime.datetime.now + t0 = nowfun() + pause = RAISE_WINDOW_TIMEOUT / float(RAISE_WINDOW_WAIT_STEPS) + timeout_delta = datetime.timedelta(0, RAISE_WINDOW_TIMEOUT) + check_interval = lambda: nowfun() - t0 < timeout_delta + + # let's assume it's a stalled lock + we_are_the_one = True + signal_event(proto.RAISE_WINDOW) + + while check_interval(): + if get_modification_ts(lock_path) > ts: + # yay! someone claimed their control over the lock. + # so the lock is alive + logger.debug('Raise window ACK-ed') + we_are_the_one = False + break + else: + time.sleep(pause) + + if we_are_the_one: + # ok, it really was a stalled lock. let's remove all + # that is left, and put only ours there. + WindowsLock.release_all_locks() + WindowsLock().get_lock() + + return we_are_the_one + + else: + logger.warning("Multi-instance checker " + "not implemented for %s" % (_sys)) + # lies, lies, lies... + return True -- cgit v1.2.3