def convert_yielded(yielded: _Yieldable) -> Future:
"""Convert a yielded object into a `.Future`.
The default implementation accepts lists, dictionaries, and
Futures. This has the side effect of starting any coroutines that
did not start themselves, similar to `asyncio.ensure_future`.
If the `~functools.singledispatch` library is available, this function
may be extended to support additional types. For example::
@convert_yielded.register(asyncio.Future)
def _(asyncio_future):
return tornado.platform.asyncio.to_tornado_future(asyncio_future)
.. versionadded:: 4.1
"""
if yielded is None or yielded is moment:
return moment
elif yielded is _null_future:
return _null_future
elif isinstance(yielded, (list, dict)):
return multi(yielded) # type: ignore
elif is_future(yielded):
return typing.cast(Future, yielded)
elif isawaitable(yielded):
return _wrap_awaitable(yielded) # type: ignore
else:
raise BadYieldError("yielded unknown object %r" % (yielded,))
def add_future(
self,
future: "Union[Future[_T], concurrent.futures.Future[_T]]",
callback: Callable[["Future[_T]"], None],
) -> None:
"""Schedules a callback on the ``IOLoop`` when the given
`.Future` is finished.
The callback is invoked with one argument, the
`.Future`.
This method only accepts `.Future` objects and not other
awaitables (unlike most of Tornado where the two are
interchangeable).
"""
if isinstance(future, Future):
# Note that we specifically do not want the inline behavior of
# tornado.concurrent.future_add_done_callback. We always want
# this callback scheduled on the next IOLoop iteration (which
# asyncio.Future always does).
#
# Wrap the callback in self._run_callback so we control
# the error logging (i.e. it goes to tornado.log.app_log
# instead of asyncio's log).
future.add_done_callback(lambda f: self._run_callback(
functools.partial(callback, future)))
else:
assert is_future(future)
# For concurrent futures, we use self.add_callback, so
# it's fine if future_add_done_callback inlines that call.
future_add_done_callback(
future, lambda f: self.add_callback(callback, future))
def maybe_future(x: Any) -> Future:
"""Converts ``x`` into a `.Future`.
If ``x`` is already a `.Future`, it is simply returned; otherwise
it is wrapped in a new `.Future`. This is suitable for use as
``result = yield gen.maybe_future(f())`` when you don't know whether
``f()`` returns a `.Future` or not.
.. deprecated:: 4.3
This function only handles ``Futures``, not other yieldable objects.
Instead of `maybe_future`, check for the non-future result types
you expect (often just ``None``), and ``yield`` anything unknown.
"""
if is_future(x):
return x
else:
fut = _create_future()
fut.set_result(x)
return fut
def run() -> None:
try:
result = func()
if result is not None:
from tornado_py3.gen import convert_yielded
result = convert_yielded(result)
except Exception:
fut = Future() # type: Future[Any]
future_cell[0] = fut
future_set_exc_info(fut, sys.exc_info())
else:
if is_future(result):
future_cell[0] = result
else:
fut = Future()
future_cell[0] = fut
fut.set_result(result)
assert future_cell[0] is not None
self.add_future(future_cell[0], lambda future: self.stop())
def multi_future(
children: Union[List[_Yieldable], Dict[Any, _Yieldable]],
quiet_exceptions: "Union[Type[Exception], Tuple[Type[Exception], ...]]" = (),
) -> "Union[Future[List], Future[Dict]]":
"""Wait for multiple asynchronous futures in parallel.
Since Tornado 6.0, this function is exactly the same as `multi`.
.. versionadded:: 4.0
.. versionchanged:: 4.2
If multiple ``Futures`` fail, any exceptions after the first (which is
raised) will be logged. Added the ``quiet_exceptions``
argument to suppress this logging for selected exception types.
.. deprecated:: 4.3
Use `multi` instead.
"""
if isinstance(children, dict):
keys = list(children.keys()) # type: Optional[List]
children_seq = children.values() # type: Iterable
else:
keys = None
children_seq = children
children_futs = list(map(convert_yielded, children_seq))
assert all(is_future(i) or isinstance(i, _NullFuture) for i in children_futs)
unfinished_children = set(children_futs)
future = _create_future()
if not children_futs:
future_set_result_unless_cancelled(future, {} if keys is not None else [])
def callback(fut: Future) -> None:
unfinished_children.remove(fut)
if not unfinished_children:
result_list = []
for f in children_futs:
try:
result_list.append(f.result())
except Exception as e:
if future.done():
if not isinstance(e, quiet_exceptions):
app_log.error(
"Multiple exceptions in yield list", exc_info=True
)
else:
future_set_exc_info(future, sys.exc_info())
if not future.done():
if keys is not None:
future_set_result_unless_cancelled(
future, dict(zip(keys, result_list))
)
else:
future_set_result_unless_cancelled(future, result_list)
listening = set() # type: Set[Future]
for f in children_futs:
if f not in listening:
listening.add(f)
future_add_done_callback(f, callback)
return future