# worker.py - master-slave parallelism support

#

# Copyright 2013 Facebook, Inc.

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

import os

import pickle

import selectors

import signal

import sys

import threading

import time

from .i18n import _

from . import (

    encoding,

    error,

    pycompat,

    scmutil,

)

def countcpus():

    '''try to count the number of CPUs on the system'''

    # posix

    try:

        n = int(os.sysconf('SC_NPROCESSORS_ONLN'))

        if n > 0:

            return n

    except (AttributeError, ValueError):

        pass

    # windows

    try:

        n = int(encoding.environ[b'NUMBER_OF_PROCESSORS'])

        if n > 0:

            return n

    except (KeyError, ValueError):

        pass

    return 1

def _numworkers(ui):

    s = ui.config(b'worker', b'numcpus')

    if s:

        try:

            n = int(s)

            if n >= 1:

                return n

        except ValueError:

            raise error.Abort(_(b'number of cpus must be an integer'))

    return min(max(countcpus(), 4), 32)

def ismainthread():

    return threading.current_thread() == threading.main_thread()

class _blockingreader:

    """Wrap unbuffered stream such that pickle.load() works with it.

    pickle.load() expects that calls to read() and readinto() read as many

    bytes as requested. On EOF, it is fine to read fewer bytes. In this case,

    pickle.load() raises an EOFError.

    """

    def __init__(self, wrapped):

        self._wrapped = wrapped

    def readline(self):

        return self._wrapped.readline()

    def readinto(self, buf):

        pos = 0

        size = len(buf)

        with memoryview(buf) as view:

            while pos < size:

                with view[pos:] as subview:

                    ret = self._wrapped.readinto(subview)

                if not ret:

                    break

                pos += ret

        return pos

    # issue multiple reads until size is fulfilled (or EOF is encountered)

    def read(self, size=-1):

        if size < 0:

            return self._wrapped.readall()

        buf = bytearray(size)

        n_read = self.readinto(buf)

        del buf[n_read:]

        return bytes(buf)

if pycompat.isposix or pycompat.iswindows:

    _STARTUP_COST = 0.01

    # The Windows worker is thread based. If tasks are CPU bound, threads

    # in the presence of the GIL result in excessive context switching and

    # this overhead can slow down execution.

    _DISALLOW_THREAD_UNSAFE = pycompat.iswindows

else:

    _STARTUP_COST = 1e30

    _DISALLOW_THREAD_UNSAFE = False

def worthwhile(ui, costperop, nops, threadsafe=True):

    """try to determine whether the benefit of multiple processes can

    outweigh the cost of starting them"""

    if not threadsafe and _DISALLOW_THREAD_UNSAFE:

        return False

    linear = costperop * nops

    workers = _numworkers(ui)

    benefit = linear - (_STARTUP_COST * workers + linear / workers)

    return benefit >= 0.15

def worker(

    ui, costperarg, func, staticargs, args, hasretval=False, threadsafe=True

):

    """run a function, possibly in parallel in multiple worker

    processes.

    returns a progress iterator

    costperarg - cost of a single task

    func - function to run. It is expected to return a progress iterator.

    staticargs - arguments to pass to every invocation of the function

    args - arguments to split into chunks, to pass to individual

    workers

    hasretval - when True, func and the current function return an progress

    iterator then a dict (encoded as an iterator that yield many (False, ..)

    then a (True, dict)). The dicts are joined in some arbitrary order, so

    overlapping keys are a bad idea.

    threadsafe - whether work items are thread safe and can be executed using

    a thread-based worker. Should be disabled for CPU heavy tasks that don't

    release the GIL.

    """

    enabled = ui.configbool(b'worker', b'enabled')

    if enabled and _platformworker is _posixworker and not ismainthread():

        # The POSIX worker has to install a handler for SIGCHLD.

        # Python up to 3.9 only allows this in the main thread.

        enabled = False

    if enabled and worthwhile(ui, costperarg, len(args), threadsafe=threadsafe):

        return _platformworker(ui, func, staticargs, args, hasretval)

    return func(*staticargs + (args,))

def _posixworker(ui, func, staticargs, args, hasretval):

    workers = _numworkers(ui)

    oldhandler = signal.getsignal(signal.SIGINT)

    signal.signal(signal.SIGINT, signal.SIG_IGN)

    pids, problem = set(), [0]

    def killworkers():

        # unregister SIGCHLD handler as all children will be killed. This

        # function shouldn't be interrupted by another SIGCHLD; otherwise pids

        # could be updated while iterating, which would cause inconsistency.

        signal.signal(signal.SIGCHLD, oldchldhandler)

        # if one worker bails, there's no good reason to wait for the rest

        for p in pids:

            try:

                os.kill(p, signal.SIGTERM)

            except ProcessLookupError:

                pass

    def waitforworkers(blocking=True):

        for pid in pids.copy():

            p = st = 0

            try:

                p, st = os.waitpid(pid, (0 if blocking else os.WNOHANG))

            except ChildProcessError:

                # child would already be reaped, but pids yet been

                # updated (maybe interrupted just after waitpid)

                pids.discard(pid)

            if not p:

                # skip subsequent steps, because child process should

                # be still running in this case

                continue

            pids.discard(p)

            st = _exitstatus(st)

            if st and not problem[0]:

                problem[0] = st

    def sigchldhandler(signum, frame):

        waitforworkers(blocking=False)

        if problem[0]:

            killworkers()

    oldchldhandler = signal.signal(signal.SIGCHLD, sigchldhandler)

    ui.flush()

    parentpid = os.getpid()

    pipes = []

    retval = {}

    for pargs in partition(args, min(workers, len(args))):

        # Every worker gets its own pipe to send results on, so we don't have to

        # implement atomic writes larger than PIPE_BUF. Each forked process has

        # its own pipe's descriptors in the local variables, and the parent

        # process has the full list of pipe descriptors (and it doesn't really

        # care what order they're in).

        rfd, wfd = os.pipe()

        pipes.append((rfd, wfd))

        # make sure we use os._exit in all worker code paths. otherwise the

        # worker may do some clean-ups which could cause surprises like

        # deadlock. see sshpeer.cleanup for example.

        # override error handling *before* fork. this is necessary because

        # exception (signal) may arrive after fork, before "pid =" assignment

        # completes, and other exception handler (dispatch.py) can lead to

        # unexpected code path without os._exit.

        ret = -1

        try:

            pid = os.fork()

            if pid == 0:

                signal.signal(signal.SIGINT, oldhandler)

                signal.signal(signal.SIGCHLD, oldchldhandler)

                def workerfunc():

                    for r, w in pipes[:-1]:

                        os.close(r)

                        os.close(w)

                    os.close(rfd)

                    with os.fdopen(wfd, 'wb') as wf:

                        for result in func(*(staticargs + (pargs,))):

                            pickle.dump(result, wf)

                            wf.flush()

                    return 0

                ret = scmutil.callcatch(ui, workerfunc)

        except:  # parent re-raises, child never returns

            if os.getpid() == parentpid:

                raise

            exctype = sys.exc_info()[0]

            force = not issubclass(exctype, KeyboardInterrupt)

            ui.traceback(force=force)

        finally:

            if os.getpid() != parentpid:

                try:

                    ui.flush()

                except:  # never returns, no re-raises

                    pass

                finally:

                    os._exit(ret & 255)

        pids.add(pid)

    selector = selectors.DefaultSelector()

    for rfd, wfd in pipes:

        os.close(wfd)

        # The stream has to be unbuffered. Otherwise, if all data is read from

        # the raw file into the buffer, the selector thinks that the FD is not

        # ready to read while pickle.load() could read from the buffer. This

        # would delay the processing of readable items.

        selector.register(os.fdopen(rfd, 'rb', 0), selectors.EVENT_READ)

    def cleanup():

        signal.signal(signal.SIGINT, oldhandler)

        waitforworkers()

        signal.signal(signal.SIGCHLD, oldchldhandler)

        selector.close()

        return problem[0]

    try:

        openpipes = len(pipes)

        while openpipes > 0:

            for key, events in selector.select():

                try:

                    # The pytype error likely goes away on a modern version of

                    # pytype having a modern typeshed snapshot.

                    # pytype: disable=wrong-arg-types

                    res = pickle.load(_blockingreader(key.fileobj))

                    # pytype: enable=wrong-arg-types

                    if hasretval and res[0]:

                        retval.update(res[1])

                    else:

                        yield res

                except EOFError:

                    selector.unregister(key.fileobj)

                    # pytype: disable=attribute-error

                    key.fileobj.close()

                    # pytype: enable=attribute-error

                    openpipes -= 1

    except:  # re-raises

        killworkers()

        cleanup()

        raise

    status = cleanup()

    if status:

        if status < 0:

            os.kill(os.getpid(), -status)

        raise error.WorkerError(status)

    if hasretval:

        yield True, retval

def _posixexitstatus(code):

    """convert a posix exit status into the same form returned by

    os.spawnv

    returns None if the process was stopped instead of exiting"""

    if os.WIFEXITED(code):

        return os.WEXITSTATUS(code)

    elif os.WIFSIGNALED(code):

        return -(os.WTERMSIG(code))

def _windowsworker(ui, func, staticargs, args, hasretval):

    class Worker(threading.Thread):

        def __init__(

            self, taskqueue, resultqueue, func, staticargs, *args, **kwargs

        ):

            threading.Thread.__init__(self, *args, **kwargs)

            self._taskqueue = taskqueue

            self._resultqueue = resultqueue

            self._func = func

            self._staticargs = staticargs

            self._interrupted = False

            self.daemon = True

            self.exception = None

        def interrupt(self):

            self._interrupted = True

        def run(self):

            try:

                while not self._taskqueue.empty():

                    try:

                        args = self._taskqueue.get_nowait()

                        for res in self._func(*self._staticargs + (args,)):

                            self._resultqueue.put(res)

                            # threading doesn't provide a native way to

                            # interrupt execution. handle it manually at every

                            # iteration.

                            if self._interrupted:

                                return

                    except pycompat.queue.Empty:

                        break

            except Exception as e:

                # store the exception such that the main thread can resurface

                # it as if the func was running without workers.

                self.exception = e

                raise

    threads = []

    def trykillworkers():

        # Allow up to 1 second to clean worker threads nicely

        cleanupend = time.time() + 1

        for t in threads:

            t.interrupt()

        for t in threads:

            remainingtime = cleanupend - time.time()

            t.join(remainingtime)

            if t.is_alive():

                # pass over the workers joining failure. it is more

                # important to surface the inital exception than the

                # fact that one of workers may be processing a large

                # task and does not get to handle the interruption.

                ui.warn(

                    _(

                        b"failed to kill worker threads while "

                        b"handling an exception\n"

                    )

                )

                return

    workers = _numworkers(ui)

    resultqueue = pycompat.queue.Queue()

    taskqueue = pycompat.queue.Queue()

    retval = {}

    # partition work to more pieces than workers to minimize the chance

    # of uneven distribution of large tasks between the workers

    for pargs in partition(args, workers * 20):

        taskqueue.put(pargs)

    for _i in range(workers):

        t = Worker(taskqueue, resultqueue, func, staticargs)

        threads.append(t)

        t.start()