/usr/lib/python3/dist-packages/tornado/concurrent.py is in python3-tornado 3.1.1-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 | #!/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 has also
been backported to older versions of Python and can be installed with
``pip install futures``). Tornado will use `concurrent.futures.Future` if
it is available; otherwise it will use a compatible class defined in this
module.
"""
from __future__ import absolute_import, division, print_function, with_statement
import functools
import sys
from tornado.stack_context import ExceptionStackContext, wrap
from tornado.util import raise_exc_info, ArgReplacer
try:
from concurrent import futures
except ImportError:
futures = None
class ReturnValueIgnoredError(Exception):
pass
class _DummyFuture(object):
def __init__(self):
self._done = False
self._result = None
self._exception = None
self._callbacks = []
def cancel(self):
return False
def cancelled(self):
return False
def running(self):
return not self._done
def done(self):
return self._done
def result(self, timeout=None):
self._check_done()
if self._exception:
raise self._exception
return self._result
def exception(self, timeout=None):
self._check_done()
if self._exception:
return self._exception
else:
return None
def add_done_callback(self, fn):
if self._done:
fn(self)
else:
self._callbacks.append(fn)
def set_result(self, result):
self._result = result
self._set_done()
def set_exception(self, exception):
self._exception = exception
self._set_done()
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:
# TODO: error handling
cb(self)
self._callbacks = None
if futures is None:
Future = _DummyFuture
else:
Future = futures.Future
class TracebackFuture(Future):
"""Subclass of `Future` which can store a traceback with
exceptions.
The traceback is automatically available in Python 3, but in the
Python 2 futures backport this information is discarded.
"""
def __init__(self):
super(TracebackFuture, self).__init__()
self.__exc_info = None
def exc_info(self):
return self.__exc_info
def set_exc_info(self, exc_info):
"""Traceback-aware replacement for
`~concurrent.futures.Future.set_exception`.
"""
self.__exc_info = exc_info
self.set_exception(exc_info[1])
def result(self):
if self.__exc_info is not None:
raise_exc_info(self.__exc_info)
else:
return super(TracebackFuture, self).result()
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(fn):
"""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.
"""
@functools.wraps(fn)
def wrapper(self, *args, **kwargs):
callback = kwargs.pop("callback", None)
future = self.executor.submit(fn, self, *args, **kwargs)
if callback:
self.io_loop.add_future(future,
lambda future: callback(future.result()))
return future
return wrapper
_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::
@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.
raise_exc_info(exc_info)
# 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``.
"""
def copy(future):
assert future is a
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)
|