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# Copyright 2017, Battelle Memorial Institute.
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'''Run gevent Greenlets in their own threads.
Supports killing threads and executing callbacks from other threads.
'''
from __future__ import absolute_import, print_function
import functools
import sys
import threading
import gevent
from gevent import GreenletExit
__all__ = ['AsyncCall', 'Threadlet', 'GreenletExit']
__author__ = 'Brandon Carpenter <brandon.carpenter@pnnl.gov>'
[docs]class Threadlet(threading.Thread):
'''A subclass of threading.Thread supporting gevent Greenlets.
The run method is executed in the thread's main greenlet and the
thread will exit when that method returns. Other threads may run
callbacks within this thread using the send() method. Unlike the
base class, threading.Thread, *daemon* is set by default.
'''
def __init__(self, *args, **kwargs):
'''This subclass adds three additional keyword arguents:
*daemon* sets the *daemon* property on the object to the given
value. It defaults to True.
*ignore_exit* is a flag indicating whether uncaught GreenletExit
exceptions will be silently ignored. It defaults to True.
*send_errors* is a flag indicating whether uncaught exceptions
occuring in callbacks run via send() should be sent to and
raised in the main greenlet. If False (the default), uncaught
exceptions will still cause tracebacks to be printed to
sys.stderr.
'''
daemon = kwargs.pop('daemon', True)
ignore = kwargs.pop('ignore_exit', True)
fatal = kwargs.pop('send_errors', False)
super(Threadlet, self).__init__(*args, **kwargs)
self.daemon = daemon
self.ignore_exit = ignore
self.send_errors = fatal
self.__async = None
self.__callbacks = []
if threading.Thread.__init__.__doc__:
__init__.__doc__ = threading.Thread.__init__.__doc__ + __init__.__doc__
[docs] def kill(self, exception=GreenletExit):
'''Raise GreenletExit or other exception in the main greenlet.'''
assert self.is_alive(), 'thread is not running'
self.send(gevent.kill, self.__greenlet, exception)
[docs] def send(self, callback, *args, **kwargs):
'''Execute callback in this thread's hub.'''
assert self.is_alive(), 'thread is not running'
self.__callbacks.append((callback, args, kwargs))
self.__async.send()
def __run_callbacks(self):
'''Execute pending callbacks.'''
hub = self.__hub
while self.__callbacks:
callback, args, kwargs = self.__callbacks.pop()
try:
callback(*args, **kwargs) # pylint: disable=star-args
except Exception: # pylint: disable=broad-except
context = None if self.send_errors else callback
hub.handle_error(context, *sys.exc_info())
# pylint: disable=no-member,invalid-name,missing-docstring
# pylint: disable=assignment-from-none,attribute-defined-outside-init
@functools.wraps(threading.Thread._Thread__bootstrap_inner)
def _Thread__bootstrap_inner(self):
run_func = self.run
def run():
self.run = run_func
try:
run_func()
except GreenletExit:
# Only raise if self.ignore_exit is False
if not getattr(self, 'ignore_exit', True):
raise
self.run = functools.wraps(run_func)(run)
# Override inner bootstrap to get thread-specific attributes
self.__greenlet = gevent.getcurrent()
self.__hub = gevent.get_hub()
self.__async = self.__hub.loop.async()
self.__async.start(self.__run_callbacks)
try:
threading.Thread._Thread__bootstrap_inner(self)
finally:
self.__async.stop()
[docs]class AsyncCall(object):
'''Send functions to another thread's gevent hub for execution.'''
def __init__(self, hub=None):
'''Install this async handler in a hub.
If hub is None, the current thread's hub is used.
'''
if hub is None:
hub = gevent.get_hub()
self.calls = calls = []
self.async = hub.loop.async()
self.async.start(functools.partial(self._run_calls, calls))
def __del__(self):
'''Stop the async handler on deletion.'''
print('deleted')
self.async.stop()
[docs] def send(self, receiver, func, *args, **kwargs):
'''Send a function to the hub to be called there.
All the arguments to this method are placed in a queue and the
hub is signaled that a function is ready. When the hub switches
to this handler, the functions are iterated over, each being
called with its results sent to the receiver.
func is called with args and kwargs in the thread of the
associated hub. If receiver is None, results are ignored and
errors are printed when exceptions occur. Otherwise, receiver is
called with the 2-tuple (exc_info, result). If an unhandled
exception occurred, exc_info is the 3-tuple returned by
sys.exc_info() and result is None. Otherwise exc_info is None
and the result is func's return value.
Note that receiver is called from the hub's thread and may
need to be injected into the thread of the receiver.
'''
self.calls.append((receiver, func, args, kwargs))
self.async.send()
@staticmethod
def _run_call(receiver, func, args, kwargs):
'''Run a pending call in its own greenlet.'''
try:
exc_info, result = None, func(*args, **kwargs) # pylint: disable=star-args
except Exception: # pylint: disable=broad-except
exc_info, result = sys.exc_info(), None
if receiver is not None:
receiver((exc_info, result))
elif exc_info:
hub = gevent.get_hub()
hub.handle_error(func, *exc_info) # pylint: disable=star-args
# This method is static to prevent a reference loop so the object
# can be garbage collected without stopping the async handler.
@classmethod
def _run_calls(cls, calls):
'''Execute pending calls.'''
while calls:
args = calls.pop()
gevent.spawn(cls._run_call, *args) # pylint: disable=star-args