mirror of
https://mau.dev/maunium/synapse.git
synced 2024-11-17 23:42:33 +01:00
56 lines
2.3 KiB
Python
56 lines
2.3 KiB
Python
# Copyright 2022 The Matrix.org Foundation C.I.C.
|
|
#
|
|
# 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.
|
|
from typing import Any, Callable, TypeVar
|
|
|
|
F = TypeVar("F", bound=Callable[..., Any])
|
|
|
|
|
|
def cancellable(function: F) -> F:
|
|
"""Marks a function as cancellable.
|
|
|
|
Servlet methods with this decorator will be cancelled if the client disconnects before we
|
|
finish processing the request.
|
|
|
|
Although this annotation is particularly useful for servlet methods, it's also
|
|
useful for intermediate functions, where it documents the fact that the function has
|
|
been audited for cancellation safety and needs to preserve that.
|
|
This then simplifies auditing new functions that call those same intermediate
|
|
functions.
|
|
|
|
During cancellation, `Deferred.cancel()` will be invoked on the `Deferred` wrapping
|
|
the method. The `cancel()` call will propagate down to the `Deferred` that is
|
|
currently being waited on. That `Deferred` will raise a `CancelledError`, which will
|
|
propagate up, as per normal exception handling.
|
|
|
|
Before applying this decorator to a new function, you MUST recursively check
|
|
that all `await`s in the function are on `async` functions or `Deferred`s that
|
|
handle cancellation cleanly, otherwise a variety of bugs may occur, ranging from
|
|
premature logging context closure, to stuck requests, to database corruption.
|
|
|
|
See the documentation page on Cancellation for more information.
|
|
|
|
Usage:
|
|
class SomeServlet(RestServlet):
|
|
@cancellable
|
|
async def on_GET(self, request: SynapseRequest) -> ...:
|
|
...
|
|
"""
|
|
|
|
function.cancellable = True # type: ignore[attr-defined]
|
|
return function
|
|
|
|
|
|
def is_function_cancellable(function: Callable[..., Any]) -> bool:
|
|
"""Checks whether a servlet method has the `@cancellable` flag."""
|
|
return getattr(function, "cancellable", False)
|