Source code for taskflow.utils.threading_utils

# -*- coding: utf-8 -*-

#    Copyright (C) 2013 Yahoo! Inc. All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import collections
import multiprocessing
import threading

import six
from six.moves import _thread

from taskflow.utils import misc


[docs]def is_alive(thread): """Helper to determine if a thread is alive (handles none safely).""" if not thread: return False return thread.is_alive()
[docs]def get_ident(): """Return the 'thread identifier' of the current thread.""" return _thread.get_ident()
[docs]def get_optimal_thread_count(default=2): """Try to guess optimal thread count for current system.""" try: return multiprocessing.cpu_count() + 1 except NotImplementedError: # NOTE(harlowja): apparently may raise so in this case we will # just setup two threads since it's hard to know what else we # should do in this situation. return default
[docs]def daemon_thread(target, *args, **kwargs): """Makes a daemon thread that calls the given target when started.""" thread = threading.Thread(target=target, args=args, kwargs=kwargs) # NOTE(skudriashev): When the main thread is terminated unexpectedly # and thread is still alive - it will prevent main thread from exiting # unless the daemon property is set to True. thread.daemon = True return thread # Container for thread creator + associated callbacks.
_ThreadBuilder = collections.namedtuple('_ThreadBuilder', ['thread_factory', 'before_start', 'after_start', 'before_join', 'after_join']) _ThreadBuilder.fields = tuple([ 'thread_factory', 'before_start', 'after_start', 'before_join', 'after_join', ])
[docs]def no_op(*args, **kwargs): """Function that does nothing."""
[docs]class ThreadBundle(object): """A group/bundle of threads that start/stop together.""" def __init__(self): self._threads = [] self._lock = threading.Lock()
[docs] def bind(self, thread_factory, before_start=None, after_start=None, before_join=None, after_join=None): """Adds a thread (to-be) into this bundle (with given callbacks). NOTE(harlowja): callbacks provided should not attempt to call mutating methods (:meth:`.stop`, :meth:`.start`, :meth:`.bind` ...) on this object as that will result in dead-lock since the lock on this object is not meant to be (and is not) reentrant... """ if before_start is None: before_start = no_op if after_start is None: after_start = no_op if before_join is None: before_join = no_op if after_join is None: after_join = no_op builder = _ThreadBuilder(thread_factory, before_start, after_start, before_join, after_join) for attr_name in builder.fields: cb = getattr(builder, attr_name) if not six.callable(cb): raise ValueError("Provided callback for argument" " '%s' must be callable" % attr_name) with self._lock: self._threads.append([ builder, # The built thread. None, # Whether the built thread was started (and should have # ran or still be running). False, ])
[docs] def start(self): """Creates & starts all associated threads (that are not running).""" count = 0 with self._lock: it = enumerate(self._threads) for i, (builder, thread, started) in it: if thread and started: continue if not thread: self._threads[i][1] = thread = builder.thread_factory() builder.before_start(thread) thread.start() count += 1 try: builder.after_start(thread) finally: # Just incase the 'after_start' callback blows up make sure # we always set this... self._threads[i][2] = started = True return count
[docs] def stop(self): """Stops & joins all associated threads (that have been started).""" count = 0 with self._lock: it = misc.reverse_enumerate(self._threads) for i, (builder, thread, started) in it: if not thread or not started: continue builder.before_join(thread) thread.join() count += 1 try: builder.after_join(thread) finally: # Just incase the 'after_join' callback blows up make sure # we always set/reset these... self._threads[i][1] = thread = None self._threads[i][2] = started = False return count
def __len__(self): """Returns how many threads (to-be) are in this bundle.""" return len(self._threads)

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