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| author | reivilibre <oliverw@matrix.org> | 2022-08-31 11:16:05 +0000 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2022-08-31 11:16:05 +0000 |
| commit | 7bc110a19e6de0572b0c9513726d13298b45ced2 (patch) | |
| tree | 98eb1a5b1f616c057508b1dcae61b0c8b3954dfd /synapse/http/server.py | |
| parent | Fix admin List Room API return type on sqlite (#13509) (diff) | |
| download | synapse-7bc110a19e6de0572b0c9513726d13298b45ced2.tar.xz | |
Generalise the `@cancellable` annotation so it can be used on functions other than just servlet methods. (#13662)
Diffstat (limited to 'synapse/http/server.py')
| -rw-r--r-- | synapse/http/server.py | 68 |
1 files changed, 3 insertions, 65 deletions
diff --git a/synapse/http/server.py b/synapse/http/server.py index 19f42159b8..6068a94b40 100644 --- a/synapse/http/server.py +++ b/synapse/http/server.py @@ -33,7 +33,6 @@ from typing import ( Optional, Pattern, Tuple, - TypeVar, Union, ) @@ -64,6 +63,7 @@ from synapse.logging.context import defer_to_thread, preserve_fn, run_in_backgro from synapse.logging.opentracing import active_span, start_active_span, trace_servlet from synapse.util import json_encoder from synapse.util.caches import intern_dict +from synapse.util.cancellation import is_function_cancellable from synapse.util.iterutils import chunk_seq if TYPE_CHECKING: @@ -94,68 +94,6 @@ HTML_ERROR_TEMPLATE = """<!DOCTYPE html> HTTP_STATUS_REQUEST_CANCELLED = 499 -F = TypeVar("F", bound=Callable[..., Any]) - - -_cancellable_method_names = frozenset( - { - # `RestServlet`, `BaseFederationServlet` and `BaseFederationServerServlet` - # methods - "on_GET", - "on_PUT", - "on_POST", - "on_DELETE", - # `_AsyncResource`, `DirectServeHtmlResource` and `DirectServeJsonResource` - # methods - "_async_render_GET", - "_async_render_PUT", - "_async_render_POST", - "_async_render_DELETE", - "_async_render_OPTIONS", - # `ReplicationEndpoint` methods - "_handle_request", - } -) - - -def cancellable(method: F) -> F: - """Marks a servlet method as cancellable. - - Methods with this decorator will be cancelled if the client disconnects before we - finish processing the request. - - 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 endpoint, 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. - - Usage: - class SomeServlet(RestServlet): - @cancellable - async def on_GET(self, request: SynapseRequest) -> ...: - ... - """ - if method.__name__ not in _cancellable_method_names and not any( - method.__name__.startswith(prefix) for prefix in _cancellable_method_names - ): - raise ValueError( - "@cancellable decorator can only be applied to servlet methods." - ) - - method.cancellable = True # type: ignore[attr-defined] - return method - - -def is_method_cancellable(method: Callable[..., Any]) -> bool: - """Checks whether a servlet method has the `@cancellable` flag.""" - return getattr(method, "cancellable", False) - - def return_json_error( f: failure.Failure, request: SynapseRequest, config: Optional[HomeServerConfig] ) -> None: @@ -389,7 +327,7 @@ class _AsyncResource(resource.Resource, metaclass=abc.ABCMeta): method_handler = getattr(self, "_async_render_%s" % (request_method,), None) if method_handler: - request.is_render_cancellable = is_method_cancellable(method_handler) + request.is_render_cancellable = is_function_cancellable(method_handler) raw_callback_return = method_handler(request) @@ -551,7 +489,7 @@ class JsonResource(DirectServeJsonResource): async def _async_render(self, request: SynapseRequest) -> Tuple[int, Any]: callback, servlet_classname, group_dict = self._get_handler_for_request(request) - request.is_render_cancellable = is_method_cancellable(callback) + request.is_render_cancellable = is_function_cancellable(callback) # Make sure we have an appropriate name for this handler in prometheus # (rather than the default of JsonResource). |