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# -*- 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 _thread
import collections
import multiprocessing
import threading
from taskflow.utils import misc
def is_alive(thread):
"""Helper to determine if a thread is alive (handles none safely)."""
if not thread:
return False
return thread.is_alive()
def get_ident():
"""Return the 'thread identifier' of the current thread."""
return _thread.get_ident()
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
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',
])
def no_op(*args, **kwargs):
"""Function that does nothing."""
class ThreadBundle(object):
"""A group/bundle of threads that start/stop together."""
def __init__(self):
self._threads = []
self._lock = threading.Lock()
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 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,
])
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
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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