offlineimap/offlineimap/threadutil.py

# Copyright (C) 2002-2011 John Goerzen & contributors
# Thread support module
#
#    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 2 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, write to the Free Software
#    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA

from threading import Lock, Thread, BoundedSemaphore
from Queue import Queue, Empty
import traceback
from thread import get_ident	# python < 2.6 support
import os.path
import sys
from offlineimap.ui import getglobalui

######################################################################
# General utilities
######################################################################

def semaphorereset(semaphore, originalstate):
    """Wait until the semaphore gets back to its original state -- all acquired
    resources released."""
    for i in range(originalstate):
        semaphore.acquire()
    # Now release these.
    for i in range(originalstate):
        semaphore.release()

class threadlist:
    def __init__(self):
        self.lock = Lock()
        self.list = []

    def add(self, thread):
        self.lock.acquire()
        try:
            self.list.append(thread)
        finally:
            self.lock.release()

    def remove(self, thread):
        self.lock.acquire()
        try:
            self.list.remove(thread)
        finally:
            self.lock.release()

    def pop(self):
        self.lock.acquire()
        try:
            if not len(self.list):
                return None
            return self.list.pop()
        finally:
            self.lock.release()

    def reset(self):
        while 1:
            thread = self.pop()
            if not thread:
                return
            thread.join()


######################################################################
# Exit-notify threads
######################################################################

exitthreads = Queue(100)

def exitnotifymonitorloop(callback):
    """An infinite "monitoring" loop watching for finished ExitNotifyThread's.

    This one is supposed to run in the main thread.
    :param callback: the function to call when a thread terminated. That
                     function is called with a single argument -- the
                     ExitNotifyThread that has terminated. The monitor will
                     not continue to monitor for other threads until
                     'callback' returns, so if it intends to perform long
                     calculations, it should start a new thread itself -- but
                     NOT an ExitNotifyThread, or else an infinite loop
                     may result.
                     Furthermore, the monitor will hold the lock all the
                     while the other thread is waiting.
    :type callback:  a callable function
    """
    global exitthreads
    while 1:
        # Loop forever and call 'callback' for each thread that exited
        try:
            # we need a timeout in the get() call, so that ctrl-c can throw
            # a SIGINT (http://bugs.python.org/issue1360). A timeout with empty
            # Queue will raise `Empty`.
            thrd = exitthreads.get(True, 60)
            callback(thrd)
        except Empty:
            pass

def threadexited(thread):
    """Called when a thread exits."""
    ui = getglobalui()
    if thread.getExitCause() == 'EXCEPTION':
        if isinstance(thread.getExitException(), SystemExit):
            # Bring a SystemExit into the main thread.
            # Do not send it back to UI layer right now.
            # Maybe later send it to ui.terminate?
            raise SystemExit
        ui.threadException(thread)      # Expected to terminate
        sys.exit(100)                   # Just in case...
    elif thread.getExitMessage() == 'SYNC_WITH_TIMER_TERMINATE':
        ui.terminate()
        # Just in case...
        sys.exit(100)
    else:
        ui.threadExited(thread)

class ExitNotifyThread(Thread):
    """This class is designed to alert a "monitor" to the fact that a
    thread has exited and to provide for the ability for it to find out
    why.  All instances are made daemon threads (setDaemon(True), so we
    bail out when the mainloop dies."""
    profiledir = None
    """class variable that is set to the profile directory if required"""

    def __init__(self, *args, **kwargs):
        super(ExitNotifyThread, self).__init__(*args, **kwargs)
        # These are all child threads that are supposed to go away when
        # the main thread is killed.
        self.setDaemon(True)

    def run(self):
        global exitthreads
        self.threadid = get_ident()
        try:
            if not ExitNotifyThread.profiledir: # normal case
                Thread.run(self)
            else:
                try:
                    import cProfile as profile
                except ImportError:
                    import profile
                prof = profile.Profile()
                try:
                    prof = prof.runctx("Thread.run(self)", globals(), locals())
                except SystemExit:
                    pass
                prof.dump_stats(os.path.join(ExitNotifyThread.profiledir,
                                "%s_%s.prof" % (self.threadid, self.getName())))
        except:
            self.setExitCause('EXCEPTION')
            if sys:
                self.setExitException(sys.exc_info()[1])
                tb = traceback.format_exc()
                self.setExitStackTrace(tb)
        else:
            self.setExitCause('NORMAL')
        if not hasattr(self, 'exitmessage'):
            self.setExitMessage(None)

        if exitthreads:
            exitthreads.put(self, True)

    def setExitCause(self, cause):
        self.exitcause = cause
    def getExitCause(self):
        """Returns the cause of the exit, one of:
        'EXCEPTION' -- the thread aborted because of an exception
        'NORMAL' -- normal termination."""
        return self.exitcause
    def setExitException(self, exc):
        self.exitexception = exc
    def getExitException(self):
        """If getExitCause() is 'EXCEPTION', holds the value from
        sys.exc_info()[1] for this exception."""
        return self.exitexception
    def setExitStackTrace(self, st):
        self.exitstacktrace = st
    def getExitStackTrace(self):
        """If getExitCause() is 'EXCEPTION', returns a string representing
        the stack trace for this exception."""
        return self.exitstacktrace
    def setExitMessage(self, msg):
        """Sets the exit message to be fetched by a subsequent call to
        getExitMessage.  This message may be any object or type except
        None."""
        self.exitmessage = msg
    def getExitMessage(self):
        """For any exit cause, returns the message previously set by
        a call to setExitMessage(), or None if there was no such message
        set."""
        return self.exitmessage

    @classmethod
    def set_profiledir(cls, directory):
        """If set, will output profile information to 'directory'"""
        cls.profiledir = directory


######################################################################
# Instance-limited threads
######################################################################

instancelimitedsems = {}
instancelimitedlock = Lock()

def initInstanceLimit(instancename, instancemax):
    """Initialize the instance-limited thread implementation to permit
    up to intancemax threads with the given instancename."""
    instancelimitedlock.acquire()
    if not instancelimitedsems.has_key(instancename):
        instancelimitedsems[instancename] = BoundedSemaphore(instancemax)
    instancelimitedlock.release()

class InstanceLimitedThread(ExitNotifyThread):
    def __init__(self, instancename, *args, **kwargs):
        self.instancename = instancename
        super(InstanceLimitedThread, self).__init__(*args, **kwargs)

    def start(self):
        instancelimitedsems[self.instancename].acquire()
        ExitNotifyThread.start(self)

    def run(self):
        try:
            ExitNotifyThread.run(self)
        finally:
            if instancelimitedsems and instancelimitedsems[self.instancename]:
                instancelimitedsems[self.instancename].release()