1 files changed, 312 insertions, 0 deletions
diff --git a/src/leap/platform_init/locks.py b/src/leap/platform_init/locks.py
new file mode 100644
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+++ b/src/leap/platform_init/locks.py
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+# -*- 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 <http://www.gnu.org/licenses/>.
+"""
+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:
+    import glob
+    import shutil
+
+    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
+                #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:
+
+    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 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