proc.py
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proc.py
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	# Copyright (c) 2008-2009 AG Projects
	# Author: Denis Bilenko
	#
	# Permission is hereby granted, free of charge, to any person obtaining a copy
	# of this software and associated documentation files (the "Software"), to deal
	# in the Software without restriction, including without limitation the rights
	# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	# copies of the Software, and to permit persons to whom the Software is
	# furnished to do so, subject to the following conditions:
	#
	# The above copyright notice and this permission notice shall be included in
	# all copies or substantial portions of the Software.
	#
	# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	# THE SOFTWARE.

	"""Advanced coroutine control.

	This module provides means to spawn, kill and link coroutines. Linking means
	subscribing to the coroutine's result, either in form of return value or
	unhandled exception.

	To create a linkable coroutine use spawn function provided by this module:

	>>> def demofunc(x, y):
	... return x / y

	>>> p = spawn(demofunc, 6, 2)

	The return value of spawn is an instance of Proc class that you can "link":

	* p.link(obj) - notify obj when the coroutine is finished

	What does "notify" means here depends on the type of `obj': a callable is
	simply called, an event or a queue is notified using send/send_exception
	methods and if `obj' is another greenlet it's killed with LinkedExited
	exception.

	Here's an example:
	>>> event = coros.event()
	>>> _ = p.link(event)
	>>> event.wait()
	3

	Now, even though `p' is finished it's still possible to link it. In this
	case the notification is performed immediatelly:

	>>> try:
	... p.link()
	... except LinkedCompleted:
	... print 'LinkedCompleted'
	LinkedCompleted

	(Without an argument, link is created to the current greenlet)

	There are also link_value and link_exception methods that only deliver a return
	value and an unhandled exception respectively (plain `link' deliver both).
	Suppose we want to spawn a greenlet to do an important part of the task; if it
	fails then there's no way to complete the task so the parent must fail as well;
	`link_exception' is useful here:

	>>> p = spawn(demofunc, 1, 0)
	>>> _ = p.link_exception()
	>>> try:
	... api.sleep(1)
	... except LinkedFailed:
	... print 'LinkedFailed'
	LinkedFailed

	One application of linking is `waitall' function: link to a bunch of coroutines
	and wait for all them to complete. Such function is provided by this module.
	"""
	import sys
	from eventlib import api, coros

	__all__ = ['LinkedExited',
	'LinkedFailed',
	'LinkedCompleted',
	'LinkedKilled',
	'ProcExit',
	'waitall',
	'killall'
	'Source',
	'Proc',
	'spawn',
	'spawn_link',
	'spawn_link_value',
	'spawn_link_exception']


	class LinkedExited(Exception):
	"""Raised when a linked proc exits"""
	msg = "%r exited"

	def __init__(self, name=None, msg=None):
	self.name = name
	if msg is None:
	msg = self.msg % self.name
	Exception.__init__(self, msg)

	class LinkedFailed(LinkedExited):
	"""Raised when a linked proc dies because of unhandled exception"""
	msg = "%r failed with %s"

	def __init__(self, name, typ, value=None, tb=None):
	msg = self.msg % (name, typ.__name__)
	LinkedExited.__init__(self, name, msg)

	class LinkedCompleted(LinkedExited):
	"""Raised when a linked proc finishes the execution cleanly"""

	msg = "%r completed successfully"

	class LinkedKilled(LinkedFailed):
	"""Raised when a linked proc dies because of unhandled GreenletExit
	(i.e. it was killed)
	"""
	msg = """%r was killed with %s"""

	def getLinkedFailed(name, typ, value=None, tb=None):
	if issubclass(typ, api.GreenletExit):
	return LinkedKilled(name, typ, value, tb)
	return LinkedFailed(name, typ, value, tb)


	class ProcExit(api.GreenletExit):
	"""Raised when this proc is killed."""


	class Link(object):

	def __init__(self, listener):
	self.listener = listener

	def cancel(self):
	self.listener = None

	def __enter__(self):
	pass

	def __exit__(self, *args):
	self.cancel()

	class LinkToEvent(Link):

	def __call__(self, source):
	if self.listener is None:
	return
	if source.has_value():
	self.listener.send(source.value)
	else:
	self.listener.send_exception(*source.exc_info())

	class LinkToGreenlet(Link):

	def __call__(self, source):
	if source.has_value():
	self.listener.throw(LinkedCompleted(source.name))
	else:
	self.listener.throw(getLinkedFailed(source.name, *source.exc_info()))

	class LinkToCallable(Link):

	def __call__(self, source):
	self.listener(source)


	def waitall(lst, trap_errors=False, queue=None):
	if queue is None:
	queue = coros.queue()
	index = -1
	for (index, linkable) in enumerate(lst):
	linkable.link(decorate_send(queue, index))
	len = index + 1
	results = [None] * len
	count = 0
	while count < len:
	try:
	index, value = queue.wait()
	except Exception:
	if not trap_errors:
	raise
	else:
	results[index] = value
	count += 1
	return results


	class decorate_send(object):

	def __init__(self, event, tag):
	self._event = event
	self._tag = tag

	def __repr__(self):
	params = (type(self).__name__, self._tag, self._event)
	return '<%s tag=%r event=%r>' % params

	def __getattr__(self, name):
	assert name != '_event'
	return getattr(self._event, name)

	def send(self, value):
	self._event.send((self._tag, value))


	def killall(procs, throw_args, *kwargs):
	if not throw_args:
	throw_args = (ProcExit, )
	wait = kwargs.pop('wait', False)
	if kwargs:
	raise TypeError('Invalid keyword argument for proc.killall(): %s' % ', '.join(kwargs.keys()))
	for g in procs:
	if not g.dead:
	api.get_hub().schedule_call_global(0, g.throw, *throw_args)
	if wait and api.getcurrent() is not api.get_hub().greenlet:
	api.sleep(0)


	class NotUsed(object):

	def __str__(self):
	return '<Source instance does not hold a value or an exception>'

	__repr__ = __str__

	_NOT_USED = NotUsed()


	def spawn_greenlet(function, *args):
	"""Create a new greenlet that will run `function(*args)'.
	The current greenlet won't be unscheduled. Keyword arguments aren't
	supported (limitation of greenlet), use spawn() to work around that.
	"""
	g = api.Greenlet(function)
	g.parent = api.get_hub().greenlet
	api.get_hub().schedule_call_global(0, g.switch, *args)
	return g


	class Source(object):
	"""Maintain a set of links to the listeners. Delegate the sent value or
	the exception to all of them.

	To set up a link, use link_value, link_exception or link method. The
	latter establishes both "value" and "exception" link. It is possible to
	link to events, queues, greenlets and callables.

	>>> source = Source()
	>>> event = coros.event()
	>>> _ = source.link(event)

	Once source's send or send_exception method is called, all the listeners
	with the right type of link will be notified ("right type" means that
	exceptions won't be delivered to "value" links and values won't be
	delivered to "exception" links). Once link has been fired it is removed.

	Notifying listeners is performed in the MAINLOOP greenlet. Under the hood
	notifying a link means executing a callback, see Link class for details. Notification
	must not attempt to switch to the hub, i.e. call any of blocking functions.

	>>> source.send('hello')
	>>> event.wait()
	'hello'

	Any error happened while sending will be logged as a regular unhandled
	exception. This won't prevent other links from being fired.

	There 3 kinds of listeners supported:

	1. If `listener' is a greenlet (regardless if it's a raw greenlet or an
	extension like Proc), a subclass of LinkedExited exception is raised
	in it.

	2. If `listener' is something with send/send_exception methods (event,
	queue, Source but not Proc) the relevant method is called.

	3. If `listener' is a callable, it is called with 1 argument (the result)
	for "value" links and with 3 arguments (typ, value, tb) for "exception"
	links.
	"""

	def __init__(self, name=None):
	self.name = name
	self._value_links = {}
	self._exception_links = {}
	self.value = _NOT_USED
	self._exc = None

	def _repr_helper(self):
	result = []
	result.append(repr(self.name))
	if self.value is not _NOT_USED:
	if self._exc is None:
	res = repr(self.value)
	if len(res)>50:
	res = res[:50]+'...'
	result.append('result=%s' % res)
	else:
	result.append('raised=%s' % (self._exc, ))
	result.append('{%s:%s}' % (len(self._value_links), len(self._exception_links)))
	return result

	def __repr__(self):
	klass = type(self).__name__
	return '<%s at %s %s>' % (klass, hex(id(self)), ' '.join(self._repr_helper()))

	def ready(self):
	return self.value is not _NOT_USED

	def has_value(self):
	return self.value is not _NOT_USED and self._exc is None

	def has_exception(self):
	return self.value is not _NOT_USED and self._exc is not None

	def exc_info(self):
	if not self._exc:
	return (None, None, None)
	elif len(self._exc)==3:
	return self._exc
	elif len(self._exc)==1:
	if isinstance(self._exc[0], type):
	return self._exc[0], None, None
	else:
	return self._exc[0].__class__, self._exc[0], None
	elif len(self._exc)==2:
	return self._exc[0], self._exc[1], None
	else:
	return self._exc

	def link_value(self, listener=None, link=None):
	if self.ready() and self._exc is not None:
	return
	if listener is None:
	listener = api.getcurrent()
	if link is None:
	link = self.getLink(listener)
	if self.ready() and listener is api.getcurrent():
	link(self)
	else:
	self._value_links[listener] = link
	if self.value is not _NOT_USED:
	self._start_send()
	return link

	def link_exception(self, listener=None, link=None):
	if self.value is not _NOT_USED and self._exc is None:
	return
	if listener is None:
	listener = api.getcurrent()
	if link is None:
	link = self.getLink(listener)
	if self.ready() and listener is api.getcurrent():
	link(self)
	else:
	self._exception_links[listener] = link
	if self.value is not _NOT_USED:
	self._start_send_exception()
	return link

	def link(self, listener=None, link=None):
	if listener is None:
	listener = api.getcurrent()
	if link is None:
	link = self.getLink(listener)
	if self.ready() and listener is api.getcurrent():
	if self._exc is None:
	link(self)
	else:
	link(self)
	else:
	self._value_links[listener] = link
	self._exception_links[listener] = link
	if self.value is not _NOT_USED:
	if self._exc is None:
	self._start_send()
	else:
	self._start_send_exception()
	return link

	def unlink(self, listener=None):
	if listener is None:
	listener = api.getcurrent()
	self._value_links.pop(listener, None)
	self._exception_links.pop(listener, None)

	@staticmethod
	def getLink(listener):
	if hasattr(listener, 'throw'):
	return LinkToGreenlet(listener)
	if hasattr(listener, 'send'):
	return LinkToEvent(listener)
	elif callable(listener):
	return LinkToCallable(listener)
	else:
	raise TypeError("Don't know how to link to %r" % (listener, ))

	def send(self, value):
	assert not self.ready(), "%s has been fired already" % self
	self.value = value
	self._exc = None
	self._start_send()

	def _start_send(self):
	api.get_hub().schedule_call_global(0, self._do_send, self._value_links.items(), self._value_links)

	def send_exception(self, *throw_args):
	assert not self.ready(), "%s has been fired already" % self
	self.value = None
	self._exc = throw_args
	self._start_send_exception()

	def _start_send_exception(self):
	api.get_hub().schedule_call_global(0, self._do_send, self._exception_links.items(), self._exception_links)

	def _do_send(self, links, consult):
	while links:
	listener, link = links.pop()
	try:
	if listener in consult:
	try:
	link(self)
	finally:
	consult.pop(listener, None)
	except:
	api.get_hub().schedule_call_global(0, self._do_send, links, consult)
	raise

	def wait(self, timeout=None, *throw_args):
	"""Wait until send() or send_exception() is called or `timeout' has
	expired. Return the argument of send or raise the argument of
	send_exception. If timeout has expired, None is returned.

	The arguments, when provided, specify how many seconds to wait and what
	to do when timeout has expired. They are treated the same way as
	api.timeout treats them.
	"""
	if self.value is not _NOT_USED:
	if self._exc is None:
	return self.value
	else:
	api.getcurrent().throw(*self._exc)
	if timeout is not None:
	timer = api.timeout(timeout, *throw_args)
	timer.__enter__()
	if timeout==0:
	if timer.__exit__(None, None, None):
	return
	else:
	try:
	api.getcurrent().throw(*timer.throw_args)
	except:
	if not timer.__exit__(*sys.exc_info()):
	raise
	return
	EXC = True
	try:
	try:
	waiter = Waiter()
	self.link(waiter)
	try:
	return waiter.wait()
	finally:
	self.unlink(waiter)
	except:
	EXC = False
	if timeout is None or not timer.__exit__(*sys.exc_info()):
	raise
	finally:
	if timeout is not None and EXC:
	timer.__exit__(None, None, None)


	class Waiter(object):

	def __init__(self):
	self.greenlet = None

	def send(self, value):
	"""Wake up the greenlet that is calling wait() currently (if there is one).
	Can only be called from get_hub().greenlet.
	"""
	assert api.getcurrent() is api.get_hub().greenlet
	if self.greenlet is not None:
	self.greenlet.switch(value)

	def send_exception(self, *throw_args):
	"""Make greenlet calling wait() wake up (if there is a wait()).
	Can only be called from get_hub().greenlet.
	"""
	assert api.getcurrent() is api.get_hub().greenlet
	if self.greenlet is not None:
	self.greenlet.throw(*throw_args)

	def wait(self):
	"""Wait until send or send_exception is called. Return value passed
	into send() or raise exception passed into send_exception().
	"""
	assert self.greenlet is None
	current = api.getcurrent()
	assert current is not api.get_hub().greenlet
	self.greenlet = current
	try:
	return api.get_hub().switch()
	finally:
	self.greenlet = None


	class Proc(Source):
	"""A linkable coroutine based on Source.
	Upon completion, delivers coroutine's result to the listeners.
	"""

	def __init__(self, name=None):
	self.greenlet = None
	Source.__init__(self, name)

	def _repr_helper(self):
	if self.greenlet is not None and self.greenlet.dead:
	dead = '(dead)'
	else:
	dead = ''
	return ['%r%s' % (self.greenlet, dead)] + Source._repr_helper(self)

	def __repr__(self):
	klass = type(self).__name__
	return '<%s %s>' % (klass, ' '.join(self._repr_helper()))

	def __nonzero__(self):
	if self.ready():
	# with current _run this does not makes any difference
	# still, let keep it there
	return False
	# otherwise bool(proc) is the same as bool(greenlet)
	if self.greenlet is not None:
	return bool(self.greenlet)

	@property
	def dead(self):
	return self.ready() or self.greenlet.dead

	@classmethod
	def spawn(cls, function, args, *kwargs):
	"""Return a new Proc instance that is scheduled to execute
	function(args, *kwargs) upon the next hub iteration.
	"""
	proc = cls()
	proc.run(function, args, *kwargs)
	return proc

	def run(self, function, args, *kwargs):
	"""Create a new greenlet to execute `function(args, *kwargs)'.
	The created greenlet is scheduled to run upon the next hub iteration.
	"""
	assert self.greenlet is None, "'run' can only be called once per instance"
	if self.name is None:
	self.name = str(function)
	self.greenlet = spawn_greenlet(self._run, function, args, kwargs)

	def _run(self, function, args, kwargs):
	"""Internal top level function.
	Execute function and send its result to the listeners.
	"""
	try:
	result = function(args, *kwargs)
	except api.GreenletExit, e:
	self.send_exception(e)
	raise
	except:
	self.send_exception(*sys.exc_info())
	raise # let mainloop log the exception
	else:
	self.send(result)

	def throw(self, *throw_args):
	"""Used internally to raise the exception.

	Behaves exactly like greenlet's 'throw' with the exception that ProcExit
	is raised by default. Do not use this function as it leaves the current
	greenlet unscheduled forever. Use kill() method instead.
	"""
	if not self.dead:
	if not throw_args:
	throw_args = (ProcExit, )
	self.greenlet.throw(*throw_args)

	def kill(self, *throw_args):
	"""Raise an exception in the greenlet. Unschedule the current greenlet
	so that this Proc can handle the exception (or die).

	The exception can be specified with throw_args. By default, ProcExit is
	raised.
	"""
	if not self.dead:
	if not throw_args:
	throw_args = (ProcExit, )
	api.get_hub().schedule_call_global(0, self.greenlet.throw, *throw_args)
	if api.getcurrent() is not api.get_hub().greenlet:
	api.sleep(0)

	# QQQ maybe Proc should not inherit from Source (because its send() and send_exception()
	# QQQ methods are for internal use only)


	spawn = Proc.spawn

	def spawn_link(function, args, *kwargs):
	p = spawn(function, args, *kwargs)
	p.link()
	return p

	def spawn_link_value(function, args, *kwargs):
	p = spawn(function, args, *kwargs)
	p.link_value()
	return p

	def spawn_link_exception(function, args, *kwargs):
	p = spawn(function, args, *kwargs)
	p.link_exception()
	return p


	def trap_errors(errors, func, args, *kwargs):
	"""DEPRECATED in favor of wrap_errors"""
	try:
	return func(args, *kwargs)
	except errors, ex:
	return ex


	class wrap_errors(object):
	"""Helper to make function return an exception, rather than raise it.

	Because every exception that is unhandled by greenlet will be logged by the hub,
	it is desirable to prevent non-error exceptions from leaving a greenlet.
	This can done with simple try/except construct:

	def func1(args, *kwargs):
	try:
	return func(args, *kwargs)
	except (A, B, C), ex:
	return ex

	wrap_errors provides a shortcut to write that in one line:

	func1 = wrap_errors((A, B, C), func)

	It also preserves __str__ and __repr__ of the original function.
	"""

	def __init__(self, errors, func):
	"""Make a new function from `func', such that it catches `errors' (an
	Exception subclass, or a tuple of Exception subclasses) and return
	it as a value.
	"""
	self.errors = errors
	self.func = func

	def __call__(self, args, *kwargs):
	try:
	return self.func(args, *kwargs)
	except self.errors, ex:
	return ex

	def __str__(self):
	return str(self.func)

	def __repr__(self):
	return repr(self.func)

	def __getattr__(self, item):
	return getattr(self.func, item)


	class RunningProcSet(object):
	"""Maintain a set of Procs that are still running, that is, automatically remove
	a proc when it's finished. Provide a way to wait/kill all of them"""

	def __init__(self, *args):
	self.procs = set(*args)
	if args:
	for p in self.args[0]:
	p.link(lambda p: self.procs.discard(p))

	def __len__(self):
	return len(self.procs)

	def __contains__(self, item):
	if isinstance(item, api.Greenlet):
	# special case for "api.getcurrent() in running_proc_set" to work
	for x in self.procs:
	if x.greenlet == item:
	return True
	else:
	return item in self.procs

	def __iter__(self):
	return iter(self.procs)

	def add(self, p):
	self.procs.add(p)
	p.link(lambda p: self.procs.discard(p))

	def spawn(self, func, args, *kwargs):
	p = spawn(func, args, *kwargs)
	self.add(p)
	return p

	def waitall(self, trap_errors=True):
	while self.procs:
	waitall(self.procs, trap_errors=trap_errors)

	def killall(self, throw_args, *kwargs):
	return killall(self.procs, throw_args, *kwargs)


	class Pool(object):

	linkable_class = Proc

	def __init__(self, limit):
	self.semaphore = coros.Semaphore(limit)

	def allocate(self):
	self.semaphore.acquire()
	g = self.linkable_class()
	g.link(lambda *_args: self.semaphore.release())
	return g


	if __name__=='__main__':
	import doctest
	doctest.testmod()

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