Optional uvloop use (#2264)

Co-authored-by: Adam Hopkins <adam@amhopkins.com>
Co-authored-by: Adam Hopkins <admhpkns@gmail.com>

sanic/app.py

@@ -69,6 +69,7 @@ from sanic.exceptions import (
     URLBuildError,
 )
 from sanic.handlers import ErrorHandler
+from sanic.helpers import _default
 from sanic.http import Stage
 from sanic.log import LOGGING_CONFIG_DEFAULTS, Colors, error_logger, logger
 from sanic.mixins.listeners import ListenerEvent
@@ -88,7 +89,7 @@ from sanic.response import BaseHTTPResponse, HTTPResponse
 from sanic.router import Router
 from sanic.server import AsyncioServer, HttpProtocol
 from sanic.server import Signal as ServerSignal
-from sanic.server import serve, serve_multiple, serve_single
+from sanic.server import serve, serve_multiple, serve_single, try_use_uvloop
 from sanic.server.protocols.websocket_protocol import WebSocketProtocol
 from sanic.server.websockets.impl import ConnectionClosed
 from sanic.signals import Signal, SignalRouter
@@ -130,6 +131,7 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
         "_task_registry",
         "_test_client",
         "_test_manager",
+        "_uvloop_setting",  # TODO: Remove in v22.6
         "asgi",
         "auto_reload",
         "auto_reload",
@@ -159,6 +161,7 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
     )
 
     _app_registry: Dict[str, "Sanic"] = {}
+    _uvloop_setting = None
     test_mode = False
 
     def __init__(
@@ -1142,6 +1145,11 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
             register_sys_signals=register_sys_signals,
         )
 
+        if self.config.USE_UVLOOP is True or (
+            self.config.USE_UVLOOP is _default and not OS_IS_WINDOWS
+        ):
+            try_use_uvloop()
+
         try:
             self.is_running = True
             self.is_stopping = False
@@ -1239,12 +1247,13 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
                 WebSocketProtocol if self.websocket_enabled else HttpProtocol
             )
 
-        # if access_log is passed explicitly change config.ACCESS_LOG
-        if access_log is not None:
-            self.config.ACCESS_LOG = access_log
-
-        if noisy_exceptions is not None:
-            self.config.NOISY_EXCEPTIONS = noisy_exceptions
+        # Set explicitly passed configuration values
+        for attribute, value in {
+            "ACCESS_LOG": access_log,
+            "NOISY_EXCEPTIONS": noisy_exceptions,
+        }.items():
+            if value is not None:
+                setattr(self.config, attribute, value)
 
         server_settings = self._helper(
             host=host,
@@ -1259,6 +1268,14 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
             run_async=return_asyncio_server,
         )
 
+        if self.config.USE_UVLOOP is not _default:
+            error_logger.warning(
+                "You are trying to change the uvloop configuration, but "
+                "this is only effective when using the run(...) method. "
+                "When using the create_server(...) method Sanic will use "
+                "the already existing loop."
+            )
+
         main_start = server_settings.pop("main_start", None)
         main_stop = server_settings.pop("main_stop", None)
         if main_start or main_stop:
@@ -1833,6 +1850,19 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
         self._future_registry.clear()
         self.signalize()
         self.finalize()
+
+        # TODO: Replace in v22.6 to check against apps in app registry
+        if (
+            self.__class__._uvloop_setting is not None
+            and self.__class__._uvloop_setting != self.config.USE_UVLOOP
+        ):
+            error_logger.warning(
+                "It looks like you're running several apps with different "
+                "uvloop settings. This is not supported and may lead to "
+                "unintended behaviour."
+            )
+        self.__class__._uvloop_setting = self.config.USE_UVLOOP
+
         ErrorHandler.finalize(self.error_handler, config=self.config)
         TouchUp.run(self)
         self.state.is_started = True

sanic/asgi.py

@@ -7,6 +7,7 @@ import sanic.app  # noqa
 
 from sanic.compat import Header
 from sanic.exceptions import ServerError
+from sanic.helpers import _default
 from sanic.http import Stage
 from sanic.models.asgi import ASGIReceive, ASGIScope, ASGISend, MockTransport
 from sanic.request import Request
@@ -53,6 +54,13 @@ class Lifespan:
         await self.asgi_app.sanic_app._server_event("init", "before")
         await self.asgi_app.sanic_app._server_event("init", "after")
 
+        if self.asgi_app.sanic_app.config.USE_UVLOOP is not _default:
+            warnings.warn(
+                "You have set the USE_UVLOOP configuration option, but Sanic "
+                "cannot control the event loop when running in ASGI mode."
+                "This option will be ignored."
+            )
+
     async def shutdown(self) -> None:
         """
         Gather the listeners to fire on server stop.

sanic/compat.py

@@ -8,6 +8,14 @@ from multidict import CIMultiDict  # type: ignore
 
 
 OS_IS_WINDOWS = os.name == "nt"
+UVLOOP_INSTALLED = False
+
+try:
+    import uvloop  # type: ignore # noqa
+
+    UVLOOP_INSTALLED = True
+except ImportError:
+    pass
 
 
 def enable_windows_color_support():

sanic/config.py

@@ -7,7 +7,7 @@ from typing import Any, Callable, Dict, Optional, Sequence, Union
 from warnings import warn
 
 from sanic.errorpages import DEFAULT_FORMAT, check_error_format
-from sanic.helpers import _default
+from sanic.helpers import Default, _default
 from sanic.http import Http
 from sanic.log import error_logger
 from sanic.utils import load_module_from_file_location, str_to_bool
@@ -38,6 +38,7 @@ DEFAULT_CONFIG = {
     "REQUEST_MAX_SIZE": 100000000,  # 100 megabytes
     "REQUEST_TIMEOUT": 60,  # 60 seconds
     "RESPONSE_TIMEOUT": 60,  # 60 seconds
+    "USE_UVLOOP": _default,
     "WEBSOCKET_MAX_SIZE": 2 ** 20,  # 1 megabyte
     "WEBSOCKET_PING_INTERVAL": 20,
     "WEBSOCKET_PING_TIMEOUT": 20,
@@ -79,6 +80,7 @@ class Config(dict, metaclass=DescriptorMeta):
     REQUEST_TIMEOUT: int
     RESPONSE_TIMEOUT: int
     SERVER_NAME: str
+    USE_UVLOOP: Union[Default, bool]
     WEBSOCKET_MAX_SIZE: int
     WEBSOCKET_PING_INTERVAL: int
     WEBSOCKET_PING_TIMEOUT: int

sanic/server/__init__.py

@@ -1,20 +1,10 @@
-import asyncio
-
 from sanic.models.server_types import ConnInfo, Signal
 from sanic.server.async_server import AsyncioServer
+from sanic.server.loop import try_use_uvloop
 from sanic.server.protocols.http_protocol import HttpProtocol
 from sanic.server.runners import serve, serve_multiple, serve_single
 
 
-try:
-    import uvloop  # type: ignore
-
-    if not isinstance(asyncio.get_event_loop_policy(), uvloop.EventLoopPolicy):
-        asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())
-except ImportError:
-    pass
-
-
 __all__ = (
     "AsyncioServer",
     "ConnInfo",
@@ -23,4 +13,5 @@ __all__ = (
     "serve",
     "serve_multiple",
     "serve_single",
+    "try_use_uvloop",
 )

sanic/server/loop.py

@@ -0,0 +1,49 @@
+import asyncio
+
+from distutils.util import strtobool
+from os import getenv
+
+from sanic.compat import OS_IS_WINDOWS
+from sanic.log import error_logger
+
+
+def try_use_uvloop() -> None:
+    """
+    Use uvloop instead of the default asyncio loop.
+    """
+    if OS_IS_WINDOWS:
+        error_logger.warning(
+            "You are trying to use uvloop, but uvloop is not compatible "
+            "with your system. You can disable uvloop completely by setting "
+            "the 'USE_UVLOOP' configuration value to false, or simply not "
+            "defining it and letting Sanic handle it for you. Sanic will now "
+            "continue to run using the default event loop."
+        )
+        return
+
+    try:
+        import uvloop  # type: ignore
+    except ImportError:
+        error_logger.warning(
+            "You are trying to use uvloop, but uvloop is not "
+            "installed in your system. In order to use uvloop "
+            "you must first install it. Otherwise, you can disable "
+            "uvloop completely by setting the 'USE_UVLOOP' "
+            "configuration value to false. Sanic will now continue "
+            "to run with the default event loop."
+        )
+        return
+
+    uvloop_install_removed = strtobool(getenv("SANIC_NO_UVLOOP", "no"))
+    if uvloop_install_removed:
+        error_logger.info(
+            "You are requesting to run Sanic using uvloop, but the "
+            "install-time 'SANIC_NO_UVLOOP' environment variable (used to "
+            "opt-out of installing uvloop with Sanic) is set to true. If "
+            "you want to prevent Sanic from overriding the event loop policy "
+            "during runtime, set the 'USE_UVLOOP' configuration value to "
+            "false."
+        )
+
+    if not isinstance(asyncio.get_event_loop_policy(), uvloop.EventLoopPolicy):
+        asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())

sanic/worker.py

@@ -7,8 +7,9 @@ import traceback
 
 from gunicorn.workers import base  # type: ignore
 
+from sanic.compat import UVLOOP_INSTALLED
 from sanic.log import logger
-from sanic.server import HttpProtocol, Signal, serve
+from sanic.server import HttpProtocol, Signal, serve, try_use_uvloop
 from sanic.server.protocols.websocket_protocol import WebSocketProtocol
 
 
@@ -17,12 +18,8 @@ try:
 except ImportError:
     ssl = None  # type: ignore
 
-try:
-    import uvloop  # type: ignore
-
-    asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())
-except ImportError:
-    pass
+if UVLOOP_INSTALLED:
+    try_use_uvloop()
 
 
 class GunicornWorker(base.Worker):