Create UVLOOP_INSTALLED constant

sanic/app.py

@@ -50,7 +50,7 @@ from sanic.asgi import ASGIApp
 from sanic.base import BaseSanic
 from sanic.blueprint_group import BlueprintGroup
 from sanic.blueprints import Blueprint
-from sanic.compat import OS_IS_WINDOWS
+from sanic.compat import OS_IS_WINDOWS, UVLOOP_INSTALLED
 from sanic.config import BASE_LOGO, SANIC_PREFIX, Config
 from sanic.exceptions import (
     InvalidUsage,
@@ -1421,10 +1421,8 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
 
     def _configure_event_loop(self):
         if self.config.USE_UVLOOP and not OS_IS_WINDOWS:
-            uvloop_success = use_uvloop()
-
-            if uvloop_success is False:
-                error_logger.warning(
+            if not UVLOOP_INSTALLED:
+                return 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 "
@@ -1433,7 +1431,8 @@ class Sanic(BaseSanic, metaclass=TouchUpMeta):
                     "to run without using uvloop."
                 )
 
-            elif strtobool(os.environ.get("SANIC_NO_UVLOOP", "no")):
+            use_uvloop()
+            if strtobool(os.environ.get("SANIC_NO_UVLOOP", "no")):
                 error_logger.warning(
                     "You are running Sanic using uvloop, but the "
                     "'SANIC_NO_UVLOOP' environment variable (used to opt-out "

sanic/compat.py

@@ -8,6 +8,13 @@ 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
 
 
 class Header(CIMultiDict):

sanic/server/__init__.py

@@ -8,19 +8,14 @@ from sanic.server.runners import serve, serve_multiple, serve_single
 
 def use_uvloop() -> bool:
     """
-    Use uvloop (if available) instead of the default
-    asyncio loop.
+    Use uvloop instead of the default asyncio loop.
     """
-    try:
-        import uvloop  # type: ignore
+    import uvloop  # type: ignore
 
-        if not isinstance(
-            asyncio.get_event_loop_policy(), uvloop.EventLoopPolicy
-        ):
-            asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())
-    except ImportError:
-        return False
-    return True
+    if not isinstance(
+        asyncio.get_event_loop_policy(), uvloop.EventLoopPolicy
+    ):
+        asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())
 
 
 __all__ = (

tests/test_app.py

@@ -9,6 +9,7 @@ from unittest.mock import Mock, patch
 import pytest
 
 from sanic import Sanic
+from sanic.compat import UVLOOP_INSTALLED
 from sanic.config import Config
 from sanic.exceptions import SanicException
 from sanic.response import text
@@ -19,15 +20,6 @@ def clear_app_registry():
     Sanic._app_registry = {}
 
 
-def uvloop_installed():
-    try:
-        import uvloop  # noqa
-
-        return True
-    except ImportError:
-        return False
-
-
 def test_app_loop_running(app):
     @app.get("/test")
     async def handler(request):
@@ -39,7 +31,7 @@ def test_app_loop_running(app):
 
 
 def test_create_asyncio_server(app):
-    if not uvloop_installed():
+    if not UVLOOP_INSTALLED:
         loop = asyncio.get_event_loop()
         asyncio_srv_coro = app.create_server(return_asyncio_server=True)
         assert isawaitable(asyncio_srv_coro)
@@ -48,7 +40,7 @@ def test_create_asyncio_server(app):
 
 
 def test_asyncio_server_no_start_serving(app):
-    if not uvloop_installed():
+    if not UVLOOP_INSTALLED:
         loop = asyncio.get_event_loop()
         asyncio_srv_coro = app.create_server(
             port=43123,
@@ -60,7 +52,7 @@ def test_asyncio_server_no_start_serving(app):
 
 
 def test_asyncio_server_start_serving(app):
-    if not uvloop_installed():
+    if not UVLOOP_INSTALLED:
         loop = asyncio.get_event_loop()
         asyncio_srv_coro = app.create_server(
             port=43124,