From 816104f2983e0f6dcded621c02c4c520e2e36da6 Mon Sep 17 00:00:00 2001 From: kali Date: Thu, 4 Apr 2013 05:16:36 +0900 Subject: detection of multiple instances using flock. sending RAISE_WINDOW leap event if we are not the main instance. --- src/leap/platform_init/__init__.py | 28 ++++ src/leap/platform_init/locks.py | 312 +++++++++++++++++++++++++++++++++++++ 2 files changed, 340 insertions(+) create mode 100644 src/leap/platform_init/locks.py (limited to 'src/leap/platform_init') diff --git a/src/leap/platform_init/__init__.py b/src/leap/platform_init/__init__.py index e69de29b..2a262a30 100644 --- a/src/leap/platform_init/__init__.py +++ b/src/leap/platform_init/__init__.py @@ -0,0 +1,28 @@ +# -*- coding: utf-8 -*- +# __init__.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 . + +""" +System constants +""" +import platform + +_system = platform.system() + +IS_WIN = True if _system == "Windows" else False +IS_MAC = True if _system == "Darwin" else False +IS_LINUX = True if _system == "Linux" else False +IS_UNIX = IS_MAC or IS_LINUX diff --git a/src/leap/platform_init/locks.py b/src/leap/platform_init/locks.py new file mode 100644 index 00000000..2cdee3d9 --- /dev/null +++ b/src/leap/platform_init/locks.py @@ -0,0 +1,312 @@ +# -*- 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 commands +import logging +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: + import errno + import glob + import shutil + import socket + + from tempfile import gettempdir + +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 + if exc.args[0] == 11: + # 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: + + 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 WindowsError 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 release_lock(self): + """ + Releases the pidfile dir for this process, by removing it. + """ + try: + shutil.rmtree(self.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 + + @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 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 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 + + @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() + signal_event(proto.RAISE_WINDOW) + 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