path: root/testing/mozharness/mozprocess/processhandler.py

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this file,
# You can obtain one at http://mozilla.org/MPL/2.0/.

import os
import select
import signal
import subprocess
import sys
import threading
import time
import traceback
from Queue import Queue
from datetime import datetime, timedelta
__all__ = ['ProcessHandlerMixin', 'ProcessHandler']

# Set the MOZPROCESS_DEBUG environment variable to 1 to see some debugging output
MOZPROCESS_DEBUG = os.getenv("MOZPROCESS_DEBUG")

# We dont use mozinfo because it is expensive to import, see bug 933558.
isWin = os.name == "nt"
isPosix = os.name == "posix" # includes MacOS X

if isWin:
    import ctypes, ctypes.wintypes, msvcrt
    from ctypes import sizeof, addressof, c_ulong, byref, POINTER, WinError, c_longlong
    import winprocess
    from qijo import JobObjectAssociateCompletionPortInformation,\
    JOBOBJECT_ASSOCIATE_COMPLETION_PORT, JobObjectExtendedLimitInformation,\
    JOBOBJECT_BASIC_LIMIT_INFORMATION, JOBOBJECT_EXTENDED_LIMIT_INFORMATION, IO_COUNTERS

class ProcessHandlerMixin(object):
    """
    A class for launching and manipulating local processes.

    :param cmd: command to run. May be a string or a list. If specified as a list, the first element will be interpreted as the command, and all additional elements will be interpreted as arguments to that command.
    :param args: list of arguments to pass to the command (defaults to None). Must not be set when `cmd` is specified as a list.
    :param cwd: working directory for command (defaults to None).
    :param env: is the environment to use for the process (defaults to os.environ).
    :param ignore_children: causes system to ignore child processes when True, defaults to False (which tracks child processes).
    :param kill_on_timeout: when True, the process will be killed when a timeout is reached. When False, the caller is responsible for killing the process. Failure to do so could cause a call to wait() to hang indefinitely. (Defaults to True.)
    :param processOutputLine: function to be called for each line of output produced by the process (defaults to None).
    :param onTimeout: function to be called when the process times out.
    :param onFinish: function to be called when the process terminates normally without timing out.
    :param kwargs: additional keyword args to pass directly into Popen.

    NOTE: Child processes will be tracked by default.  If for any reason
    we are unable to track child processes and ignore_children is set to False,
    then we will fall back to only tracking the root process.  The fallback
    will be logged.
    """

    class Process(subprocess.Popen):
        """
        Represents our view of a subprocess.
        It adds a kill() method which allows it to be stopped explicitly.
        """

        MAX_IOCOMPLETION_PORT_NOTIFICATION_DELAY = 180
        MAX_PROCESS_KILL_DELAY = 30

        def __init__(self,
                     args,
                     bufsize=0,
                     executable=None,
                     stdin=None,
                     stdout=None,
                     stderr=None,
                     preexec_fn=None,
                     close_fds=False,
                     shell=False,
                     cwd=None,
                     env=None,
                     universal_newlines=False,
                     startupinfo=None,
                     creationflags=0,
                     ignore_children=False):

            # Parameter for whether or not we should attempt to track child processes
            self._ignore_children = ignore_children

            if not self._ignore_children and not isWin:
                # Set the process group id for linux systems
                # Sets process group id to the pid of the parent process
                # NOTE: This prevents you from using preexec_fn and managing
                #       child processes, TODO: Ideally, find a way around this
                def setpgidfn():
                    os.setpgid(0, 0)
                preexec_fn = setpgidfn

            try:
                subprocess.Popen.__init__(self, args, bufsize, executable,
                                          stdin, stdout, stderr,
                                          preexec_fn, close_fds,
                                          shell, cwd, env,
                                          universal_newlines, startupinfo, creationflags)
            except OSError, e:
                print >> sys.stderr, args
                raise

        def __del__(self, _maxint=sys.maxint):
            if isWin:
                if self._handle:
                    if hasattr(self, '_internal_poll'):
                        self._internal_poll(_deadstate=_maxint)
                    else:
                        self.poll(_deadstate=sys.maxint)
                if self._handle or self._job or self._io_port:
                    self._cleanup()
            else:
                subprocess.Popen.__del__(self)

        def kill(self, sig=None):
            self.returncode = 0
            if isWin:
                if not self._ignore_children and self._handle and self._job:
                    winprocess.TerminateJobObject(self._job, winprocess.ERROR_CONTROL_C_EXIT)
                    self.returncode = winprocess.GetExitCodeProcess(self._handle)
                elif self._handle:
                    err = None
                    try:
                        winprocess.TerminateProcess(self._handle, winprocess.ERROR_CONTROL_C_EXIT)
                    except:
                        err = "Could not terminate process"
                    self.returncode = winprocess.GetExitCodeProcess(self._handle)
                    self._cleanup()
                    if err is not None:
                        raise OSError(err)
            else:
                sig = sig or signal.SIGKILL
                if not self._ignore_children:
                    try:
                        os.killpg(self.pid, sig)
                    except BaseException, e:
                        if getattr(e, "errno", None) != 3:
                            # Error 3 is "no such process", which is ok
                            print >> sys.stdout, "Could not kill process, could not find pid: %s, assuming it's already dead" % self.pid
                else:
                    os.kill(self.pid, sig)
                self.returncode = -sig

            self._cleanup()
            return self.returncode

        def wait(self):
            """ Popen.wait
                Called to wait for a running process to shut down and return
                its exit code
                Returns the main process's exit code
            """
            # This call will be different for each OS
            self.returncode = self._wait()
            self._cleanup()
            return self.returncode

        """ Private Members of Process class """

        if isWin:
            # Redefine the execute child so that we can track process groups
            def _execute_child(self, *args_tuple):
                # workaround for bug 950894
                if sys.hexversion < 0x02070600: # prior to 2.7.6
                    (args, executable, preexec_fn, close_fds,
                     cwd, env, universal_newlines, startupinfo,
                     creationflags, shell,
                     p2cread, p2cwrite,
                     c2pread, c2pwrite,
                     errread, errwrite) = args_tuple
                    to_close = set()
                else: # 2.7.6 and later
                    (args, executable, preexec_fn, close_fds,
                     cwd, env, universal_newlines, startupinfo,
                     creationflags, shell, to_close,
                     p2cread, p2cwrite,
                     c2pread, c2pwrite,
                     errread, errwrite) = args_tuple
                if not isinstance(args, basestring):
                    args = subprocess.list2cmdline(args)

                # Always or in the create new process group
                creationflags |= winprocess.CREATE_NEW_PROCESS_GROUP

                if startupinfo is None:
                    startupinfo = winprocess.STARTUPINFO()

                if None not in (p2cread, c2pwrite, errwrite):
                    startupinfo.dwFlags |= winprocess.STARTF_USESTDHANDLES
                    startupinfo.hStdInput = int(p2cread)
                    startupinfo.hStdOutput = int(c2pwrite)
                    startupinfo.hStdError = int(errwrite)
                if shell:
                    startupinfo.dwFlags |= winprocess.STARTF_USESHOWWINDOW
                    startupinfo.wShowWindow = winprocess.SW_HIDE
                    comspec = os.environ.get("COMSPEC", "cmd.exe")
                    args = comspec + " /c " + args

                # determine if we can create create a job
                canCreateJob = winprocess.CanCreateJobObject()

                # Ensure we write a warning message if we are falling back
                if not canCreateJob and not self._ignore_children:
                    # We can't create job objects AND the user wanted us to
                    # Warn the user about this.
                    print >> sys.stderr, "ProcessManager UNABLE to use job objects to manage child processes"

                # set process creation flags
                creationflags |= winprocess.CREATE_SUSPENDED
                creationflags |= winprocess.CREATE_UNICODE_ENVIRONMENT
                if canCreateJob:
                    creationflags |= winprocess.CREATE_BREAKAWAY_FROM_JOB
                else:
                    # Since we've warned, we just log info here to inform you
                    # of the consequence of setting ignore_children = True
                    print "ProcessManager NOT managing child processes"

                # create the process
                hp, ht, pid, tid = winprocess.CreateProcess(
                    executable, args,
                    None, None, # No special security
                    1, # Must inherit handles!
                    creationflags,
                    winprocess.EnvironmentBlock(env),
                    cwd, startupinfo)
                self._child_created = True
                self._handle = hp
                self._thread = ht
                self.pid = pid
                self.tid = tid

                if not self._ignore_children and canCreateJob:
                    try:
                        # We create a new job for this process, so that we can kill
                        # the process and any sub-processes
                        # Create the IO Completion Port
                        self._io_port = winprocess.CreateIoCompletionPort()
                        self._job = winprocess.CreateJobObject()

                        # Now associate the io comp port and the job object
                        joacp = JOBOBJECT_ASSOCIATE_COMPLETION_PORT(winprocess.COMPKEY_JOBOBJECT,
                                                                    self._io_port)
                        winprocess.SetInformationJobObject(self._job,
                                                          JobObjectAssociateCompletionPortInformation,
                                                          addressof(joacp),
                                                          sizeof(joacp)
                                                          )

                        # Allow subprocesses to break away from us - necessary for
                        # flash with protected mode
                        jbli = JOBOBJECT_BASIC_LIMIT_INFORMATION(
                                                c_longlong(0), # per process time limit (ignored)
                                                c_longlong(0), # per job user time limit (ignored)
                                                winprocess.JOB_OBJECT_LIMIT_BREAKAWAY_OK,
                                                0, # min working set (ignored)
                                                0, # max working set (ignored)
                                                0, # active process limit (ignored)
                                                None, # affinity (ignored)
                                                0, # Priority class (ignored)
                                                0, # Scheduling class (ignored)
                                                )

                        iocntr = IO_COUNTERS()
                        jeli = JOBOBJECT_EXTENDED_LIMIT_INFORMATION(
                                                jbli, # basic limit info struct
                                                iocntr,    # io_counters (ignored)
                                                0,    # process mem limit (ignored)
                                                0,    # job mem limit (ignored)
                                                0,    # peak process limit (ignored)
                                                0)    # peak job limit (ignored)

                        winprocess.SetInformationJobObject(self._job,
                                                           JobObjectExtendedLimitInformation,
                                                           addressof(jeli),
                                                           sizeof(jeli)
                                                           )

                        # Assign the job object to the process
                        winprocess.AssignProcessToJobObject(self._job, int(hp))

                        # It's overkill, but we use Queue to signal between threads
                        # because it handles errors more gracefully than event or condition.
                        self._process_events = Queue()

                        # Spin up our thread for managing the IO Completion Port
                        self._procmgrthread = threading.Thread(target = self._procmgr)
                    except:
                        print >> sys.stderr, """Exception trying to use job objects;
falling back to not using job objects for managing child processes"""
                        tb = traceback.format_exc()
                        print >> sys.stderr, tb
                        # Ensure no dangling handles left behind
                        self._cleanup_job_io_port()
                else:
                    self._job = None

                winprocess.ResumeThread(int(ht))
                if getattr(self, '_procmgrthread', None):
                    self._procmgrthread.start()
                ht.Close()

                for i in (p2cread, c2pwrite, errwrite):
                    if i is not None:
                        i.Close()

            # Windows Process Manager - watches the IO Completion Port and
            # keeps track of child processes
            def _procmgr(self):
                if not (self._io_port) or not (self._job):
                    return

                try:
                    self._poll_iocompletion_port()
                except KeyboardInterrupt:
                    raise KeyboardInterrupt

            def _poll_iocompletion_port(self):
                # Watch the IO Completion port for status
                self._spawned_procs = {}
                countdowntokill = 0

                if MOZPROCESS_DEBUG:
                    print "DBG::MOZPROC Self.pid value is: %s" % self.pid

                while True:
                    msgid = c_ulong(0)
                    compkey = c_ulong(0)
                    pid = c_ulong(0)
                    portstatus = winprocess.GetQueuedCompletionStatus(self._io_port,
                                                                      byref(msgid),
                                                                      byref(compkey),
                                                                      byref(pid),
                                                                      5000)

                    # If the countdowntokill has been activated, we need to check
                    # if we should start killing the children or not.
                    if countdowntokill != 0:
                        diff = datetime.now() - countdowntokill
                        # Arbitrarily wait 3 minutes for windows to get its act together
                        # Windows sometimes takes a small nap between notifying the
                        # IO Completion port and actually killing the children, and we
                        # don't want to mistake that situation for the situation of an unexpected
                        # parent abort (which is what we're looking for here).
                        if diff.seconds > self.MAX_IOCOMPLETION_PORT_NOTIFICATION_DELAY:
                            print >> sys.stderr, "Parent process %s exited with children alive:" % self.pid
                            print >> sys.stderr, "PIDS: %s" %  ', '.join([str(i) for i in self._spawned_procs])
                            print >> sys.stderr, "Attempting to kill them..."
                            self.kill()
                            self._process_events.put({self.pid: 'FINISHED'})

                    if not portstatus:
                        # Check to see what happened
                        errcode = winprocess.GetLastError()
                        if errcode == winprocess.ERROR_ABANDONED_WAIT_0:
                            # Then something has killed the port, break the loop
                            print >> sys.stderr, "IO Completion Port unexpectedly closed"
                            break
                        elif errcode == winprocess.WAIT_TIMEOUT:
                            # Timeouts are expected, just keep on polling
                            continue
                        else:
                            print >> sys.stderr, "Error Code %s trying to query IO Completion Port, exiting" % errcode
                            raise WinError(errcode)
                            break

                    if compkey.value == winprocess.COMPKEY_TERMINATE.value:
                        if MOZPROCESS_DEBUG:
                            print "DBG::MOZPROC compkeyterminate detected"
                        # Then we're done
                        break

                    # Check the status of the IO Port and do things based on it
                    if compkey.value == winprocess.COMPKEY_JOBOBJECT.value:
                        if msgid.value == winprocess.JOB_OBJECT_MSG_ACTIVE_PROCESS_ZERO:
                            # No processes left, time to shut down
                            # Signal anyone waiting on us that it is safe to shut down
                            if MOZPROCESS_DEBUG:
                                print "DBG::MOZPROC job object msg active processes zero"
                            self._process_events.put({self.pid: 'FINISHED'})
                            break
                        elif msgid.value == winprocess.JOB_OBJECT_MSG_NEW_PROCESS:
                            # New Process started
                            # Add the child proc to our list in case our parent flakes out on us
                            # without killing everything.
                            if pid.value != self.pid:
                                self._spawned_procs[pid.value] = 1
                                if MOZPROCESS_DEBUG:
                                    print "DBG::MOZPROC new process detected with pid value: %s" % pid.value
                        elif msgid.value == winprocess.JOB_OBJECT_MSG_EXIT_PROCESS:
                            if MOZPROCESS_DEBUG:
                                print "DBG::MOZPROC process id %s exited normally" % pid.value
                            # One process exited normally
                            if pid.value == self.pid and len(self._spawned_procs) > 0:
                                # Parent process dying, start countdown timer
                                countdowntokill = datetime.now()
                            elif pid.value in self._spawned_procs:
                                # Child Process died remove from list
                                del(self._spawned_procs[pid.value])
                        elif msgid.value == winprocess.JOB_OBJECT_MSG_ABNORMAL_EXIT_PROCESS:
                            # One process existed abnormally
                            if MOZPROCESS_DEBUG:
                                print "DBG::MOZPROC process id %s existed abnormally" % pid.value
                            if pid.value == self.pid and len(self._spawned_procs) > 0:
                                # Parent process dying, start countdown timer
                                countdowntokill = datetime.now()
                            elif pid.value in self._spawned_procs:
                                # Child Process died remove from list
                                del self._spawned_procs[pid.value]
                        else:
                            # We don't care about anything else
                            if MOZPROCESS_DEBUG:
                                print "DBG::MOZPROC We got a message %s" % msgid.value
                            pass

            def _wait(self):

                # First, check to see if the process is still running
                if self._handle:
                    self.returncode = winprocess.GetExitCodeProcess(self._handle)
                else:
                    # Dude, the process is like totally dead!
                    return self.returncode

                # Python 2.5 uses isAlive versus is_alive use the proper one
                threadalive = False
                if hasattr(self, "_procmgrthread"):
                    if hasattr(self._procmgrthread, 'is_alive'):
                        threadalive = self._procmgrthread.is_alive()
                    else:
                        threadalive = self._procmgrthread.isAlive()
                if self._job and threadalive:
                    # Then we are managing with IO Completion Ports
                    # wait on a signal so we know when we have seen the last
                    # process come through.
                    # We use queues to synchronize between the thread and this
                    # function because events just didn't have robust enough error
                    # handling on pre-2.7 versions
                    err = None
                    try:
                        # timeout is the max amount of time the procmgr thread will wait for
                        # child processes to shutdown before killing them with extreme prejudice.
                        item = self._process_events.get(timeout=self.MAX_IOCOMPLETION_PORT_NOTIFICATION_DELAY +
                                                                self.MAX_PROCESS_KILL_DELAY)
                        if item[self.pid] == 'FINISHED':
                            self._process_events.task_done()
                    except:
                        err = "IO Completion Port failed to signal process shutdown"
                    # Either way, let's try to get this code
                    if self._handle:
                        self.returncode = winprocess.GetExitCodeProcess(self._handle)
                    self._cleanup()

                    if err is not None:
                        raise OSError(err)


                else:
                    # Not managing with job objects, so all we can reasonably do
                    # is call waitforsingleobject and hope for the best

                    if MOZPROCESS_DEBUG and not self._ignore_children:
                        print "DBG::MOZPROC NOT USING JOB OBJECTS!!!"
                    # First, make sure we have not already ended
                    if self.returncode != winprocess.STILL_ACTIVE:
                        self._cleanup()
                        return self.returncode

                    rc = None
                    if self._handle:
                        rc = winprocess.WaitForSingleObject(self._handle, -1)

                    if rc == winprocess.WAIT_TIMEOUT:
                        # The process isn't dead, so kill it
                        print "Timed out waiting for process to close, attempting TerminateProcess"
                        self.kill()
                    elif rc == winprocess.WAIT_OBJECT_0:
                        # We caught WAIT_OBJECT_0, which indicates all is well
                        print "Single process terminated successfully"
                        self.returncode = winprocess.GetExitCodeProcess(self._handle)
                    else:
                        # An error occured we should probably throw
                        rc = winprocess.GetLastError()
                        if rc:
                            raise WinError(rc)

                    self._cleanup()

                return self.returncode

            def _cleanup_job_io_port(self):
                """ Do the job and IO port cleanup separately because there are
                    cases where we want to clean these without killing _handle
                    (i.e. if we fail to create the job object in the first place)
                """
                if getattr(self, '_job') and self._job != winprocess.INVALID_HANDLE_VALUE:
                    self._job.Close()
                    self._job = None
                else:
                    # If windows already freed our handle just set it to none
                    # (saw this intermittently while testing)
                    self._job = None

                if getattr(self, '_io_port', None) and self._io_port != winprocess.INVALID_HANDLE_VALUE:
                    self._io_port.Close()
                    self._io_port = None
                else:
                    self._io_port = None

                if getattr(self, '_procmgrthread', None):
                    self._procmgrthread = None

            def _cleanup(self):
                self._cleanup_job_io_port()
                if self._thread and self._thread != winprocess.INVALID_HANDLE_VALUE:
                    self._thread.Close()
                    self._thread = None
                else:
                    self._thread = None

                if self._handle and self._handle != winprocess.INVALID_HANDLE_VALUE:
                    self._handle.Close()
                    self._handle = None
                else:
                    self._handle = None

        elif isPosix:

            def _wait(self):
                """ Haven't found any reason to differentiate between these platforms
                    so they all use the same wait callback.  If it is necessary to
                    craft different styles of wait, then a new _wait method
                    could be easily implemented.
                """

                if not self._ignore_children:
                    try:
                        # os.waitpid return value:
                        # > [...] a tuple containing its pid and exit status
                        # > indication: a 16-bit number, whose low byte is the
                        # > signal number that killed the process, and whose
                        # > high byte is the exit status (if the signal number
                        # > is zero)
                        # - http://docs.python.org/2/library/os.html#os.wait
                        status = os.waitpid(self.pid, 0)[1]

                        # For consistency, format status the same as subprocess'
                        # returncode attribute
                        if status > 255:
                            return status >> 8
                        return -status
                    except OSError, e:
                        if getattr(e, "errno", None) != 10:
                            # Error 10 is "no child process", which could indicate normal
                            # close
                            print >> sys.stderr, "Encountered error waiting for pid to close: %s" % e
                            raise
                        return 0

                else:
                    # For non-group wait, call base class
                    subprocess.Popen.wait(self)
                    return self.returncode

            def _cleanup(self):
                pass

        else:
            # An unrecognized platform, we will call the base class for everything
            print >> sys.stderr, "Unrecognized platform, process groups may not be managed properly"

            def _wait(self):
                self.returncode = subprocess.Popen.wait(self)
                return self.returncode

            def _cleanup(self):
                pass

    def __init__(self,
                 cmd,
                 args=None,
                 cwd=None,
                 env=None,
                 ignore_children = False,
                 kill_on_timeout = True,
                 processOutputLine=(),
                 onTimeout=(),
                 onFinish=(),
                 **kwargs):
        self.cmd = cmd
        self.args = args
        self.cwd = cwd
        self.didTimeout = False
        self._ignore_children = ignore_children
        self._kill_on_timeout = kill_on_timeout
        self.keywordargs = kwargs
        self.outThread = None
        self.read_buffer = ''

        if env is None:
            env = os.environ.copy()
        self.env = env

        # handlers
        self.processOutputLineHandlers = list(processOutputLine)
        self.onTimeoutHandlers = list(onTimeout)
        self.onFinishHandlers = list(onFinish)

        # It is common for people to pass in the entire array with the cmd and
        # the args together since this is how Popen uses it.  Allow for that.
        if isinstance(self.cmd, list):
            if self.args != None:
                raise TypeError("cmd and args must not both be lists")
            (self.cmd, self.args) = (self.cmd[0], self.cmd[1:])
        elif self.args is None:
            self.args = []

    @property
    def timedOut(self):
        """True if the process has timed out."""
        return self.didTimeout

    @property
    def commandline(self):
        """the string value of the command line (command + args)"""
        return subprocess.list2cmdline([self.cmd] + self.args)

    def run(self, timeout=None, outputTimeout=None):
        """
        Starts the process.

        If timeout is not None, the process will be allowed to continue for
        that number of seconds before being killed. If the process is killed
        due to a timeout, the onTimeout handler will be called.

        If outputTimeout is not None, the process will be allowed to continue
        for that number of seconds without producing any output before
        being killed.
        """
        self.didTimeout = False
        self.startTime = datetime.now()

        # default arguments
        args = dict(stdout=subprocess.PIPE,
                    stderr=subprocess.STDOUT,
                    cwd=self.cwd,
                    env=self.env,
                    ignore_children=self._ignore_children)

        # build process arguments
        args.update(self.keywordargs)

        # launch the process
        self.proc = self.Process([self.cmd] + self.args, **args)

        self.processOutput(timeout=timeout, outputTimeout=outputTimeout)

    def kill(self, sig=None):
        """
        Kills the managed process.

        If you created the process with 'ignore_children=False' (the
        default) then it will also also kill all child processes spawned by
        it. If you specified 'ignore_children=True' when creating the
        process, only the root process will be killed.

        Note that this does not manage any state, save any output etc,
        it immediately kills the process.

        :param sig: Signal used to kill the process, defaults to SIGKILL
                    (has no effect on Windows)
        """
        try:
            return self.proc.kill(sig=sig)
        except AttributeError:
            # Try to print a relevant error message.
            if not self.proc:
                print >> sys.stderr, "Unable to kill Process because call to ProcessHandler constructor failed."
            else:
                raise

    def readWithTimeout(self, f, timeout):
        """
        Try to read a line of output from the file object *f*.

        *f* must be a  pipe, like the *stdout* member of a subprocess.Popen
        object created with stdout=PIPE. If no output
        is received within *timeout* seconds, return a blank line.

        Returns a tuple (line, did_timeout), where *did_timeout* is True
        if the read timed out, and False otherwise.
        """
        # Calls a private member because this is a different function based on
        # the OS
        return self._readWithTimeout(f, timeout)

    def processOutputLine(self, line):
        """Called for each line of output that a process sends to stdout/stderr."""
        for handler in self.processOutputLineHandlers:
            handler(line)

    def onTimeout(self):
        """Called when a process times out."""
        for handler in self.onTimeoutHandlers:
            handler()

    def onFinish(self):
        """Called when a process finishes without a timeout."""
        for handler in self.onFinishHandlers:
            handler()

    def processOutput(self, timeout=None, outputTimeout=None):
        """
        Handle process output until the process terminates or times out.

        If timeout is not None, the process will be allowed to continue for
        that number of seconds before being killed.

        If outputTimeout is not None, the process will be allowed to continue
        for that number of seconds without producing any output before
        being killed.
        """
        def _processOutput():
            self.didTimeout = False
            logsource = self.proc.stdout

            lineReadTimeout = None
            if timeout:
                lineReadTimeout = timeout - (datetime.now() - self.startTime).seconds
            elif outputTimeout:
                lineReadTimeout = outputTimeout

            (lines, self.didTimeout) = self.readWithTimeout(logsource, lineReadTimeout)
            while lines != "":
                for line in lines.splitlines():
                    self.processOutputLine(line.rstrip())

                if self.didTimeout:
                    break

                if timeout:
                    lineReadTimeout = timeout - (datetime.now() - self.startTime).seconds
                (lines, self.didTimeout) = self.readWithTimeout(logsource, lineReadTimeout)

            if self.didTimeout:
                if self._kill_on_timeout:
                    self.proc.kill()
                self.onTimeout()
            else:
                self.onFinish()

        if not hasattr(self, 'proc'):
            self.run()

        if not self.outThread:
            self.outThread = threading.Thread(target=_processOutput)
            self.outThread.daemon = True
            self.outThread.start()


    def wait(self, timeout=None):
        """
        Waits until all output has been read and the process is
        terminated.

        If timeout is not None, will return after timeout seconds.
        This timeout only causes the wait function to return and
        does not kill the process.

        Returns the process' exit code. A None value indicates the
        process hasn't terminated yet. A negative value -N indicates
        the process was killed by signal N (Unix only).
        """
        if self.outThread:
            # Thread.join() blocks the main thread until outThread is finished
            # wake up once a second in case a keyboard interrupt is sent
            count = 0
            while self.outThread.isAlive():
                self.outThread.join(timeout=1)
                count += 1
                if timeout and count > timeout:
                    return None

        return self.proc.wait()

    # TODO Remove this method when consumers have been fixed
    def waitForFinish(self, timeout=None):
        print >> sys.stderr, "MOZPROCESS WARNING: ProcessHandler.waitForFinish() is deprecated, " \
                             "use ProcessHandler.wait() instead"
        return self.wait(timeout=timeout)


    ### Private methods from here on down. Thar be dragons.

    if isWin:
        # Windows Specific private functions are defined in this block
        PeekNamedPipe = ctypes.windll.kernel32.PeekNamedPipe
        GetLastError = ctypes.windll.kernel32.GetLastError

        def _readWithTimeout(self, f, timeout):
            if timeout is None:
                # shortcut to allow callers to pass in "None" for no timeout.
                return (f.readline(), False)
            x = msvcrt.get_osfhandle(f.fileno())
            l = ctypes.c_long()
            done = time.time() + timeout
            while time.time() < done:
                if self.PeekNamedPipe(x, None, 0, None, ctypes.byref(l), None) == 0:
                    err = self.GetLastError()
                    if err == 38 or err == 109: # ERROR_HANDLE_EOF || ERROR_BROKEN_PIPE
                        return ('', False)
                    else:
                        raise OSError("readWithTimeout got error: %d", err)
                if l.value > 0:
                    # we're assuming that the output is line-buffered,
                    # which is not unreasonable
                    return (f.readline(), False)
                time.sleep(0.01)
            return ('', True)

    else:
        # Generic
        def _readWithTimeout(self, f, timeout):
            while True:
                try:
                    (r, w, e) = select.select([f], [], [], timeout)
                except:
                    # return a blank line
                    return ('', True)

                if len(r) == 0:
                    return ('', True)

                output = os.read(f.fileno(), 4096)
                if not output:
                    output = self.read_buffer
                    self.read_buffer = ''
                    return (output, False)
                self.read_buffer += output
                if '\n' not in self.read_buffer:
                    time.sleep(0.01)
                    continue
                tmp = self.read_buffer.split('\n')
                lines, self.read_buffer = tmp[:-1], tmp[-1]
                real_lines = [x for x in lines if x != '']
                if not real_lines:
                    time.sleep(0.01)
                    continue
                break
            return ('\n'.join(lines), False)

    @property
    def pid(self):
        return self.proc.pid


### default output handlers
### these should be callables that take the output line

def print_output(line):
    print line

class StoreOutput(object):
    """accumulate stdout"""

    def __init__(self):
        self.output = []

    def __call__(self, line):
        self.output.append(line)

class LogOutput(object):
    """pass output to a file"""

    def __init__(self, filename):
        self.filename = filename
        self.file = None

    def __call__(self, line):
        if self.file is None:
            self.file = file(self.filename, 'a')
        self.file.write(line + '\n')
        self.file.flush()

    def __del__(self):
        if self.file is not None:
            self.file.close()

### front end class with the default handlers

class ProcessHandler(ProcessHandlerMixin):
    """
    Convenience class for handling processes with default output handlers.

    If no processOutputLine keyword argument is specified, write all
    output to stdout.  Otherwise, the function specified by this argument
    will be called for each line of output; the output will not be written
    to stdout automatically.

    If storeOutput==True, the output produced by the process will be saved
    as self.output.

    If logfile is not None, the output produced by the process will be
    appended to the given file.
    """

    def __init__(self, cmd, logfile=None, storeOutput=True, **kwargs):
        kwargs.setdefault('processOutputLine', [])

        # Print to standard output only if no outputline provided
        if not kwargs['processOutputLine']:
            kwargs['processOutputLine'].append(print_output)

        if logfile:
            logoutput = LogOutput(logfile)
            kwargs['processOutputLine'].append(logoutput)

        self.output = None
        if storeOutput:
            storeoutput = StoreOutput()
            self.output = storeoutput.output
            kwargs['processOutputLine'].append(storeoutput)

        ProcessHandlerMixin.__init__(self, cmd, **kwargs)