mirror of
https://github.com/SickGear/SickGear.git
synced 2024-12-11 05:33:37 +00:00
516 lines
18 KiB
Python
516 lines
18 KiB
Python
#!/usr/bin/env python
|
|
#
|
|
# Copyright 2012 Facebook
|
|
#
|
|
# 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.
|
|
"""Utilities for working with threads and ``Futures``.
|
|
|
|
``Futures`` are a pattern for concurrent programming introduced in
|
|
Python 3.2 in the `concurrent.futures` package. This package defines
|
|
a mostly-compatible `Future` class designed for use from coroutines,
|
|
as well as some utility functions for interacting with the
|
|
`concurrent.futures` package.
|
|
"""
|
|
from __future__ import absolute_import, division, print_function, with_statement
|
|
|
|
import functools
|
|
import platform
|
|
import textwrap
|
|
import traceback
|
|
import sys
|
|
|
|
from tornado.log import app_log
|
|
from tornado.stack_context import ExceptionStackContext, wrap
|
|
from tornado.util import raise_exc_info, ArgReplacer, is_finalizing
|
|
|
|
try:
|
|
from concurrent import futures
|
|
except ImportError:
|
|
futures = None
|
|
|
|
try:
|
|
import typing
|
|
except ImportError:
|
|
typing = None
|
|
|
|
|
|
# Can the garbage collector handle cycles that include __del__ methods?
|
|
# This is true in cpython beginning with version 3.4 (PEP 442).
|
|
_GC_CYCLE_FINALIZERS = (platform.python_implementation() == 'CPython' and
|
|
sys.version_info >= (3, 4))
|
|
|
|
|
|
class ReturnValueIgnoredError(Exception):
|
|
pass
|
|
|
|
# This class and associated code in the future object is derived
|
|
# from the Trollius project, a backport of asyncio to Python 2.x - 3.x
|
|
|
|
|
|
class _TracebackLogger(object):
|
|
"""Helper to log a traceback upon destruction if not cleared.
|
|
|
|
This solves a nasty problem with Futures and Tasks that have an
|
|
exception set: if nobody asks for the exception, the exception is
|
|
never logged. This violates the Zen of Python: 'Errors should
|
|
never pass silently. Unless explicitly silenced.'
|
|
|
|
However, we don't want to log the exception as soon as
|
|
set_exception() is called: if the calling code is written
|
|
properly, it will get the exception and handle it properly. But
|
|
we *do* want to log it if result() or exception() was never called
|
|
-- otherwise developers waste a lot of time wondering why their
|
|
buggy code fails silently.
|
|
|
|
An earlier attempt added a __del__() method to the Future class
|
|
itself, but this backfired because the presence of __del__()
|
|
prevents garbage collection from breaking cycles. A way out of
|
|
this catch-22 is to avoid having a __del__() method on the Future
|
|
class itself, but instead to have a reference to a helper object
|
|
with a __del__() method that logs the traceback, where we ensure
|
|
that the helper object doesn't participate in cycles, and only the
|
|
Future has a reference to it.
|
|
|
|
The helper object is added when set_exception() is called. When
|
|
the Future is collected, and the helper is present, the helper
|
|
object is also collected, and its __del__() method will log the
|
|
traceback. When the Future's result() or exception() method is
|
|
called (and a helper object is present), it removes the the helper
|
|
object, after calling its clear() method to prevent it from
|
|
logging.
|
|
|
|
One downside is that we do a fair amount of work to extract the
|
|
traceback from the exception, even when it is never logged. It
|
|
would seem cheaper to just store the exception object, but that
|
|
references the traceback, which references stack frames, which may
|
|
reference the Future, which references the _TracebackLogger, and
|
|
then the _TracebackLogger would be included in a cycle, which is
|
|
what we're trying to avoid! As an optimization, we don't
|
|
immediately format the exception; we only do the work when
|
|
activate() is called, which call is delayed until after all the
|
|
Future's callbacks have run. Since usually a Future has at least
|
|
one callback (typically set by 'yield From') and usually that
|
|
callback extracts the callback, thereby removing the need to
|
|
format the exception.
|
|
|
|
PS. I don't claim credit for this solution. I first heard of it
|
|
in a discussion about closing files when they are collected.
|
|
"""
|
|
|
|
__slots__ = ('exc_info', 'formatted_tb')
|
|
|
|
def __init__(self, exc_info):
|
|
self.exc_info = exc_info
|
|
self.formatted_tb = None
|
|
|
|
def activate(self):
|
|
exc_info = self.exc_info
|
|
if exc_info is not None:
|
|
self.exc_info = None
|
|
self.formatted_tb = traceback.format_exception(*exc_info)
|
|
|
|
def clear(self):
|
|
self.exc_info = None
|
|
self.formatted_tb = None
|
|
|
|
def __del__(self, is_finalizing=is_finalizing):
|
|
if not is_finalizing() and self.formatted_tb:
|
|
app_log.error('Future exception was never retrieved: %s',
|
|
''.join(self.formatted_tb).rstrip())
|
|
|
|
|
|
class Future(object):
|
|
"""Placeholder for an asynchronous result.
|
|
|
|
A ``Future`` encapsulates the result of an asynchronous
|
|
operation. In synchronous applications ``Futures`` are used
|
|
to wait for the result from a thread or process pool; in
|
|
Tornado they are normally used with `.IOLoop.add_future` or by
|
|
yielding them in a `.gen.coroutine`.
|
|
|
|
`tornado.concurrent.Future` is similar to
|
|
`concurrent.futures.Future`, but not thread-safe (and therefore
|
|
faster for use with single-threaded event loops).
|
|
|
|
In addition to ``exception`` and ``set_exception``, methods ``exc_info``
|
|
and ``set_exc_info`` are supported to capture tracebacks in Python 2.
|
|
The traceback is automatically available in Python 3, but in the
|
|
Python 2 futures backport this information is discarded.
|
|
This functionality was previously available in a separate class
|
|
``TracebackFuture``, which is now a deprecated alias for this class.
|
|
|
|
.. versionchanged:: 4.0
|
|
`tornado.concurrent.Future` is always a thread-unsafe ``Future``
|
|
with support for the ``exc_info`` methods. Previously it would
|
|
be an alias for the thread-safe `concurrent.futures.Future`
|
|
if that package was available and fall back to the thread-unsafe
|
|
implementation if it was not.
|
|
|
|
.. versionchanged:: 4.1
|
|
If a `.Future` contains an error but that error is never observed
|
|
(by calling ``result()``, ``exception()``, or ``exc_info()``),
|
|
a stack trace will be logged when the `.Future` is garbage collected.
|
|
This normally indicates an error in the application, but in cases
|
|
where it results in undesired logging it may be necessary to
|
|
suppress the logging by ensuring that the exception is observed:
|
|
``f.add_done_callback(lambda f: f.exception())``.
|
|
"""
|
|
def __init__(self):
|
|
self._done = False
|
|
self._result = None
|
|
self._exc_info = None
|
|
|
|
self._log_traceback = False # Used for Python >= 3.4
|
|
self._tb_logger = None # Used for Python <= 3.3
|
|
|
|
self._callbacks = []
|
|
|
|
# Implement the Python 3.5 Awaitable protocol if possible
|
|
# (we can't use return and yield together until py33).
|
|
if sys.version_info >= (3, 3):
|
|
exec(textwrap.dedent("""
|
|
def __await__(self):
|
|
return (yield self)
|
|
"""))
|
|
else:
|
|
# Py2-compatible version for use with cython.
|
|
def __await__(self):
|
|
result = yield self
|
|
# StopIteration doesn't take args before py33,
|
|
# but Cython recognizes the args tuple.
|
|
e = StopIteration()
|
|
e.args = (result,)
|
|
raise e
|
|
|
|
def cancel(self):
|
|
"""Cancel the operation, if possible.
|
|
|
|
Tornado ``Futures`` do not support cancellation, so this method always
|
|
returns False.
|
|
"""
|
|
return False
|
|
|
|
def cancelled(self):
|
|
"""Returns True if the operation has been cancelled.
|
|
|
|
Tornado ``Futures`` do not support cancellation, so this method
|
|
always returns False.
|
|
"""
|
|
return False
|
|
|
|
def running(self):
|
|
"""Returns True if this operation is currently running."""
|
|
return not self._done
|
|
|
|
def done(self):
|
|
"""Returns True if the future has finished running."""
|
|
return self._done
|
|
|
|
def _clear_tb_log(self):
|
|
self._log_traceback = False
|
|
if self._tb_logger is not None:
|
|
self._tb_logger.clear()
|
|
self._tb_logger = None
|
|
|
|
def result(self, timeout=None):
|
|
"""If the operation succeeded, return its result. If it failed,
|
|
re-raise its exception.
|
|
|
|
This method takes a ``timeout`` argument for compatibility with
|
|
`concurrent.futures.Future` but it is an error to call it
|
|
before the `Future` is done, so the ``timeout`` is never used.
|
|
"""
|
|
self._clear_tb_log()
|
|
if self._result is not None:
|
|
return self._result
|
|
if self._exc_info is not None:
|
|
raise_exc_info(self._exc_info)
|
|
self._check_done()
|
|
return self._result
|
|
|
|
def exception(self, timeout=None):
|
|
"""If the operation raised an exception, return the `Exception`
|
|
object. Otherwise returns None.
|
|
|
|
This method takes a ``timeout`` argument for compatibility with
|
|
`concurrent.futures.Future` but it is an error to call it
|
|
before the `Future` is done, so the ``timeout`` is never used.
|
|
"""
|
|
self._clear_tb_log()
|
|
if self._exc_info is not None:
|
|
return self._exc_info[1]
|
|
else:
|
|
self._check_done()
|
|
return None
|
|
|
|
def add_done_callback(self, fn):
|
|
"""Attaches the given callback to the `Future`.
|
|
|
|
It will be invoked with the `Future` as its argument when the Future
|
|
has finished running and its result is available. In Tornado
|
|
consider using `.IOLoop.add_future` instead of calling
|
|
`add_done_callback` directly.
|
|
"""
|
|
if self._done:
|
|
fn(self)
|
|
else:
|
|
self._callbacks.append(fn)
|
|
|
|
def set_result(self, result):
|
|
"""Sets the result of a ``Future``.
|
|
|
|
It is undefined to call any of the ``set`` methods more than once
|
|
on the same object.
|
|
"""
|
|
self._result = result
|
|
self._set_done()
|
|
|
|
def set_exception(self, exception):
|
|
"""Sets the exception of a ``Future.``"""
|
|
self.set_exc_info(
|
|
(exception.__class__,
|
|
exception,
|
|
getattr(exception, '__traceback__', None)))
|
|
|
|
def exc_info(self):
|
|
"""Returns a tuple in the same format as `sys.exc_info` or None.
|
|
|
|
.. versionadded:: 4.0
|
|
"""
|
|
self._clear_tb_log()
|
|
return self._exc_info
|
|
|
|
def set_exc_info(self, exc_info):
|
|
"""Sets the exception information of a ``Future.``
|
|
|
|
Preserves tracebacks on Python 2.
|
|
|
|
.. versionadded:: 4.0
|
|
"""
|
|
self._exc_info = exc_info
|
|
self._log_traceback = True
|
|
if not _GC_CYCLE_FINALIZERS:
|
|
self._tb_logger = _TracebackLogger(exc_info)
|
|
|
|
try:
|
|
self._set_done()
|
|
finally:
|
|
# Activate the logger after all callbacks have had a
|
|
# chance to call result() or exception().
|
|
if self._log_traceback and self._tb_logger is not None:
|
|
self._tb_logger.activate()
|
|
self._exc_info = exc_info
|
|
|
|
def _check_done(self):
|
|
if not self._done:
|
|
raise Exception("DummyFuture does not support blocking for results")
|
|
|
|
def _set_done(self):
|
|
self._done = True
|
|
for cb in self._callbacks:
|
|
try:
|
|
cb(self)
|
|
except Exception:
|
|
app_log.exception('Exception in callback %r for %r',
|
|
cb, self)
|
|
self._callbacks = None
|
|
|
|
# On Python 3.3 or older, objects with a destructor part of a reference
|
|
# cycle are never destroyed. It's no longer the case on Python 3.4 thanks to
|
|
# the PEP 442.
|
|
if _GC_CYCLE_FINALIZERS:
|
|
def __del__(self, is_finalizing=is_finalizing):
|
|
if is_finalizing() or not self._log_traceback:
|
|
# set_exception() was not called, or result() or exception()
|
|
# has consumed the exception
|
|
return
|
|
|
|
tb = traceback.format_exception(*self._exc_info)
|
|
|
|
app_log.error('Future %r exception was never retrieved: %s',
|
|
self, ''.join(tb).rstrip())
|
|
|
|
TracebackFuture = Future
|
|
|
|
if futures is None:
|
|
FUTURES = Future # type: typing.Union[type, typing.Tuple[type, ...]]
|
|
else:
|
|
FUTURES = (futures.Future, Future)
|
|
|
|
|
|
def is_future(x):
|
|
return isinstance(x, FUTURES)
|
|
|
|
|
|
class DummyExecutor(object):
|
|
def submit(self, fn, *args, **kwargs):
|
|
future = TracebackFuture()
|
|
try:
|
|
future.set_result(fn(*args, **kwargs))
|
|
except Exception:
|
|
future.set_exc_info(sys.exc_info())
|
|
return future
|
|
|
|
def shutdown(self, wait=True):
|
|
pass
|
|
|
|
dummy_executor = DummyExecutor()
|
|
|
|
|
|
def run_on_executor(*args, **kwargs):
|
|
"""Decorator to run a synchronous method asynchronously on an executor.
|
|
|
|
The decorated method may be called with a ``callback`` keyword
|
|
argument and returns a future.
|
|
|
|
The `.IOLoop` and executor to be used are determined by the ``io_loop``
|
|
and ``executor`` attributes of ``self``. To use different attributes,
|
|
pass keyword arguments to the decorator::
|
|
|
|
@run_on_executor(executor='_thread_pool')
|
|
def foo(self):
|
|
pass
|
|
|
|
.. versionchanged:: 4.2
|
|
Added keyword arguments to use alternative attributes.
|
|
"""
|
|
def run_on_executor_decorator(fn):
|
|
executor = kwargs.get("executor", "executor")
|
|
io_loop = kwargs.get("io_loop", "io_loop")
|
|
|
|
@functools.wraps(fn)
|
|
def wrapper(self, *args, **kwargs):
|
|
callback = kwargs.pop("callback", None)
|
|
future = getattr(self, executor).submit(fn, self, *args, **kwargs)
|
|
if callback:
|
|
getattr(self, io_loop).add_future(
|
|
future, lambda future: callback(future.result()))
|
|
return future
|
|
return wrapper
|
|
if args and kwargs:
|
|
raise ValueError("cannot combine positional and keyword args")
|
|
if len(args) == 1:
|
|
return run_on_executor_decorator(args[0])
|
|
elif len(args) != 0:
|
|
raise ValueError("expected 1 argument, got %d", len(args))
|
|
return run_on_executor_decorator
|
|
|
|
|
|
_NO_RESULT = object()
|
|
|
|
|
|
def return_future(f):
|
|
"""Decorator to make a function that returns via callback return a
|
|
`Future`.
|
|
|
|
The wrapped function should take a ``callback`` keyword argument
|
|
and invoke it with one argument when it has finished. To signal failure,
|
|
the function can simply raise an exception (which will be
|
|
captured by the `.StackContext` and passed along to the ``Future``).
|
|
|
|
From the caller's perspective, the callback argument is optional.
|
|
If one is given, it will be invoked when the function is complete
|
|
with `Future.result()` as an argument. If the function fails, the
|
|
callback will not be run and an exception will be raised into the
|
|
surrounding `.StackContext`.
|
|
|
|
If no callback is given, the caller should use the ``Future`` to
|
|
wait for the function to complete (perhaps by yielding it in a
|
|
`.gen.engine` function, or passing it to `.IOLoop.add_future`).
|
|
|
|
Usage:
|
|
|
|
.. testcode::
|
|
|
|
@return_future
|
|
def future_func(arg1, arg2, callback):
|
|
# Do stuff (possibly asynchronous)
|
|
callback(result)
|
|
|
|
@gen.engine
|
|
def caller(callback):
|
|
yield future_func(arg1, arg2)
|
|
callback()
|
|
|
|
..
|
|
|
|
Note that ``@return_future`` and ``@gen.engine`` can be applied to the
|
|
same function, provided ``@return_future`` appears first. However,
|
|
consider using ``@gen.coroutine`` instead of this combination.
|
|
"""
|
|
replacer = ArgReplacer(f, 'callback')
|
|
|
|
@functools.wraps(f)
|
|
def wrapper(*args, **kwargs):
|
|
future = TracebackFuture()
|
|
callback, args, kwargs = replacer.replace(
|
|
lambda value=_NO_RESULT: future.set_result(value),
|
|
args, kwargs)
|
|
|
|
def handle_error(typ, value, tb):
|
|
future.set_exc_info((typ, value, tb))
|
|
return True
|
|
exc_info = None
|
|
with ExceptionStackContext(handle_error):
|
|
try:
|
|
result = f(*args, **kwargs)
|
|
if result is not None:
|
|
raise ReturnValueIgnoredError(
|
|
"@return_future should not be used with functions "
|
|
"that return values")
|
|
except:
|
|
exc_info = sys.exc_info()
|
|
raise
|
|
if exc_info is not None:
|
|
# If the initial synchronous part of f() raised an exception,
|
|
# go ahead and raise it to the caller directly without waiting
|
|
# for them to inspect the Future.
|
|
future.result()
|
|
|
|
# If the caller passed in a callback, schedule it to be called
|
|
# when the future resolves. It is important that this happens
|
|
# just before we return the future, or else we risk confusing
|
|
# stack contexts with multiple exceptions (one here with the
|
|
# immediate exception, and again when the future resolves and
|
|
# the callback triggers its exception by calling future.result()).
|
|
if callback is not None:
|
|
def run_callback(future):
|
|
result = future.result()
|
|
if result is _NO_RESULT:
|
|
callback()
|
|
else:
|
|
callback(future.result())
|
|
future.add_done_callback(wrap(run_callback))
|
|
return future
|
|
return wrapper
|
|
|
|
|
|
def chain_future(a, b):
|
|
"""Chain two futures together so that when one completes, so does the other.
|
|
|
|
The result (success or failure) of ``a`` will be copied to ``b``, unless
|
|
``b`` has already been completed or cancelled by the time ``a`` finishes.
|
|
"""
|
|
def copy(future):
|
|
assert future is a
|
|
if b.done():
|
|
return
|
|
if (isinstance(a, TracebackFuture) and
|
|
isinstance(b, TracebackFuture) and
|
|
a.exc_info() is not None):
|
|
b.set_exc_info(a.exc_info())
|
|
elif a.exception() is not None:
|
|
b.set_exception(a.exception())
|
|
else:
|
|
b.set_result(a.result())
|
|
a.add_done_callback(copy)
|