Files
deb-python-eventlet/eventlet/proc.py
Sergey Shepelev 203e629212 PEP-8 fixes
2014-08-27 10:21:55 +04:00

740 lines
22 KiB
Python

"""
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 :func:`spawn` is an instance of :class:`Proc` class that
you can "link":
* ``p.link(obj)`` - notify *obj* when the coroutine is finished
What "notify" means here depends on the type of *obj*: a callable is simply
called, an :class:`~eventlet.coros.Event` or a :class:`~eventlet.coros.queue`
is notified using ``send``/``send_exception`` methods and if *obj* is another
greenlet it's killed with :class:`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, the link is created to the current greenlet)
There are also :meth:`~eventlet.proc.Source.link_value` and
:func:`link_exception` methods that only deliver a return value and an
unhandled exception respectively (plain :meth:`~eventlet.proc.Source.link`
delivers 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; :meth:`~eventlet.proc.Source.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 :func:`waitall` function: link to a bunch of
coroutines and wait for all them to complete. Such a function is provided by
this module.
"""
import sys
from eventlet import api, coros, hubs
from eventlet.support import six
import warnings
warnings.warn(
"The proc module is deprecated! Please use the greenthread "
"module, or any of the many other Eventlet cross-coroutine "
"primitives, instead.",
DeprecationWarning, stacklevel=2)
__all__ = ['LinkedExited',
'LinkedFailed',
'LinkedCompleted',
'LinkedKilled',
'ProcExit',
'Link',
'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 LinkedCompleted(LinkedExited):
"""Raised when a linked proc finishes the execution cleanly"""
msg = "%r completed successfully"
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 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):
"""
A link to a greenlet, triggered when the greenlet exits.
"""
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:
hubs.get_hub().schedule_call_global(0, g.throw, *throw_args)
if wait and api.getcurrent() is not hubs.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 :func:`spawn` to work around that.
"""
g = api.Greenlet(function)
g.parent = hubs.get_hub().greenlet
hubs.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 :meth:`link_value`, :meth:`link_exception` or
:meth:`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 :meth:`send` or :meth:`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 :class:`Link` class
for details. Notification *must not* attempt to switch to the hub, i.e.
call any 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 :class:`Proc`), a subclass of :class:`LinkedExited`
exception is raised in it.
2. If *listener* is something with send/send_exception methods (event,
queue, :class:`Source` but not :class:`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 hasattr(listener, '__call__'):
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):
links_items = list(six.iteritems(self._value_links))
hubs.get_hub().schedule_call_global(0, self._do_send, 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):
links_items = list(six.iteritems(self._exception_links))
hubs.get_hub().schedule_call_global(0, self._do_send, 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:
hubs.get_hub().schedule_call_global(0, self._do_send, links, consult)
raise
def wait(self, timeout=None, *throw_args):
"""Wait until :meth:`send` or :meth:`send_exception` is called or
*timeout* has expired. Return the argument of :meth:`send` or raise the
argument of :meth:`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
:func:`~eventlet.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 hubs.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 hubs.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 hubs.get_hub().greenlet
self.greenlet = current
try:
return hubs.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)
__bool__ = __nonzero__
@property
def dead(self):
return self.ready() or self.greenlet.dead
@classmethod
def spawn(cls, function, *args, **kwargs):
"""Return a new :class:`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:
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
:class:`ProcExit` is raised by default. Do not use this function as it
leaves the current greenlet unscheduled forever. Use :meth:`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 :class:`Proc` can handle the exception (or die).
The exception can be specified with *throw_args*. By default,
:class:`ProcExit` is raised.
"""
if not self.dead:
if not throw_args:
throw_args = (ProcExit, )
hubs.get_hub().schedule_call_global(0, self.greenlet.throw, *throw_args)
if api.getcurrent() is not hubs.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
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) as 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 as 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 :class:`Proc` s 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=False):
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