Allow fork in limited cases (#2624)

sanic/application/ext.py

@@ -8,11 +8,6 @@
 if TYPE_CHECKING:
     from sanic import Sanic
 
-    try:
-        from sanic_ext import Extend  # type: ignore
-    except ImportError:
-        ...
-
 
 def setup_ext(app: Sanic, *, fail: bool = False, **kwargs):
     if not app.config.AUTO_EXTEND:
@@ -33,7 +28,7 @@ def setup_ext(app: Sanic, *, fail: bool = False, **kwargs):
         return
 
     if not getattr(app, "_ext", None):
-        Ext: Extend = getattr(sanic_ext, "Extend")
+        Ext = getattr(sanic_ext, "Extend")
         app._ext = Ext(app, **kwargs)
 
         return app.ext

sanic/compat.py

@@ -3,10 +3,22 @@
 import signal
 import sys
 
-from typing import Awaitable
+from contextlib import contextmanager
+from typing import Awaitable, Union
 
 from multidict import CIMultiDict  # type: ignore
 
+from sanic.helpers import Default
+
+
+if sys.version_info < (3, 8):  # no cov
+    StartMethod = Union[Default, str]
+else:  # no cov
+    from typing import Literal
+
+    StartMethod = Union[
+        Default, Literal["fork"], Literal["forkserver"], Literal["spawn"]
+    ]
 
 OS_IS_WINDOWS = os.name == "nt"
 UVLOOP_INSTALLED = False
@@ -19,6 +31,16 @@
     pass
 
 
+@contextmanager
+def use_context(method: StartMethod):
+    from sanic import Sanic
+
+    orig = Sanic.start_method
+    Sanic.start_method = method
+    yield
+    Sanic.start_method = orig
+
+
 def enable_windows_color_support():
     import ctypes
 

sanic/mixins/startup.py

@@ -40,9 +40,9 @@
 from sanic.application.motd import MOTD
 from sanic.application.state import ApplicationServerInfo, Mode, ServerStage
 from sanic.base.meta import SanicMeta
-from sanic.compat import OS_IS_WINDOWS, is_atty
+from sanic.compat import OS_IS_WINDOWS, StartMethod, is_atty
 from sanic.exceptions import ServerKilled
-from sanic.helpers import Default
+from sanic.helpers import Default, _default
 from sanic.http.constants import HTTP
 from sanic.http.tls import get_ssl_context, process_to_context
 from sanic.http.tls.context import SanicSSLContext
@@ -88,6 +88,7 @@ class StartupMixin(metaclass=SanicMeta):
     state: ApplicationState
     websocket_enabled: bool
     multiplexer: WorkerMultiplexer
+    start_method: StartMethod = _default
 
     def setup_loop(self):
         if not self.asgi:
@@ -692,12 +693,17 @@ def should_auto_reload(cls) -> bool:
         return any(app.state.auto_reload for app in cls._app_registry.values())
 
     @classmethod
-    def _get_context(cls) -> BaseContext:
-        method = (
-            "spawn"
-            if "linux" not in sys.platform or cls.should_auto_reload()
-            else "fork"
+    def _get_startup_method(cls) -> str:
+        return (
+            cls.start_method
+            if not isinstance(cls.start_method, Default)
+            else "spawn"
         )
+
+    @classmethod
+    def _get_context(cls) -> BaseContext:
+        method = cls._get_startup_method()
+        logger.debug("Creating multiprocessing context using '%s'", method)
         return get_context(method)
 
     @classmethod

tests/conftest.py

@@ -8,7 +8,7 @@
 
 from contextlib import suppress
 from logging import LogRecord
-from typing import List, Tuple
+from typing import Any, Dict, List, Tuple
 from unittest.mock import MagicMock
 
 import pytest
@@ -54,7 +54,7 @@ async def _handler(request):
     "uuid": lambda: str(uuid.uuid1()),
 }
 
-CACHE = {}
+CACHE: Dict[str, Any] = {}
 
 
 class RouteStringGenerator:
@@ -147,6 +147,7 @@ def app(request):
         for target, method_name in TouchUp._registry:
             CACHE[method_name] = getattr(target, method_name)
     app = Sanic(slugify.sub("-", request.node.name))
+
     yield app
     for target, method_name in TouchUp._registry:
         setattr(target, method_name, CACHE[method_name])

tests/test_app.py

@@ -349,11 +349,11 @@ def test_get_app_does_not_exist():
     with pytest.raises(
         SanicException,
         match="Sanic app name 'does-not-exist' not found.\n"
-            "App instantiation must occur outside "
-            "if __name__ == '__main__' "
-            "block or by using an AppLoader.\nSee "
-            "https://sanic.dev/en/guide/deployment/app-loader.html"
-            " for more details."
+        "App instantiation must occur outside "
+        "if __name__ == '__main__' "
+        "block or by using an AppLoader.\nSee "
+        "https://sanic.dev/en/guide/deployment/app-loader.html"
+        " for more details.",
     ):
         Sanic.get_app("does-not-exist")
 

tests/test_cli.py

@@ -117,7 +117,13 @@ def test_error_with_path_as_instance_without_simple_arg(caplog):
     ),
 )
 def test_tls_options(cmd: Tuple[str, ...], caplog):
-    command = ["fake.server.app", *cmd, "--port=9999", "--debug"]
+    command = [
+        "fake.server.app",
+        *cmd,
+        "--port=9999",
+        "--debug",
+        "--single-process",
+    ]
     lines = capture(command, caplog)
     assert "Goin' Fast @ https://127.0.0.1:9999" in lines
 

tests/test_coffee.py

@@ -39,7 +39,7 @@ async def shutdown(*_):
     with patch("sys.stdout.isatty") as isatty:
         isatty.return_value = True
         with caplog.at_level(logging.DEBUG):
-            app.make_coffee()
+            app.make_coffee(single_process=True)
 
     # Only in the regular logo
     assert "    ▄███ █████ ██    " not in caplog.text

tests/test_create_task.py

@@ -2,7 +2,6 @@
 import sys
 
 from threading import Event
-from unittest.mock import Mock
 
 import pytest
 
@@ -75,7 +74,7 @@ async def stop(app, _):
 
         app.stop()
 
-    app.run()
+    app.run(single_process=True)
 
 
 def test_named_task_called(app):

tests/test_logging.py

@@ -10,8 +10,7 @@
 import sanic
 
 from sanic import Sanic
-from sanic.log import Colors
-from sanic.log import LOGGING_CONFIG_DEFAULTS, logger
+from sanic.log import LOGGING_CONFIG_DEFAULTS, Colors, logger
 from sanic.response import text
 
 
@@ -254,11 +253,11 @@ def log_info(request):
 
 
 def test_colors_enum_format():
-    assert f'{Colors.END}' == Colors.END.value
-    assert f'{Colors.BOLD}' == Colors.BOLD.value
-    assert f'{Colors.BLUE}' == Colors.BLUE.value
-    assert f'{Colors.GREEN}' == Colors.GREEN.value
-    assert f'{Colors.PURPLE}' == Colors.PURPLE.value
-    assert f'{Colors.RED}' == Colors.RED.value
-    assert f'{Colors.SANIC}' == Colors.SANIC.value
-    assert f'{Colors.YELLOW}' == Colors.YELLOW.value
+    assert f"{Colors.END}" == Colors.END.value
+    assert f"{Colors.BOLD}" == Colors.BOLD.value
+    assert f"{Colors.BLUE}" == Colors.BLUE.value
+    assert f"{Colors.GREEN}" == Colors.GREEN.value
+    assert f"{Colors.PURPLE}" == Colors.PURPLE.value
+    assert f"{Colors.RED}" == Colors.RED.value
+    assert f"{Colors.SANIC}" == Colors.SANIC.value
+    assert f"{Colors.YELLOW}" == Colors.YELLOW.value

tests/test_multiprocessing.py

@@ -3,6 +3,7 @@
 import pickle
 import random
 import signal
+import sys
 
 from asyncio import sleep
 
@@ -11,6 +12,7 @@
 from sanic_testing.testing import HOST, PORT
 
 from sanic import Blueprint, text
+from sanic.compat import use_context
 from sanic.log import logger
 from sanic.server.socket import configure_socket
 
@@ -20,6 +22,10 @@
     reason="SIGALRM is not implemented for this platform, we have to come "
     "up with another timeout strategy to test these",
 )
+@pytest.mark.skipif(
+    sys.platform not in ("linux", "darwin"),
+    reason="This test requires fork context",
+)
 def test_multiprocessing(app):
     """Tests that the number of children we produce is correct"""
     # Selects a number at random so we can spot check
@@ -37,7 +43,8 @@ def stop_on_alarm(*args):
 
     signal.signal(signal.SIGALRM, stop_on_alarm)
     signal.alarm(2)
-    app.run(HOST, 4120, workers=num_workers, debug=True)
+    with use_context("fork"):
+        app.run(HOST, 4120, workers=num_workers, debug=True)
 
     assert len(process_list) == num_workers + 1
 
@@ -136,6 +143,10 @@ def stop_on_alarm(*args):
     not hasattr(signal, "SIGALRM"),
     reason="SIGALRM is not implemented for this platform",
 )
+@pytest.mark.skipif(
+    sys.platform not in ("linux", "darwin"),
+    reason="This test requires fork context",
+)
 def test_multiprocessing_with_blueprint(app):
     # Selects a number at random so we can spot check
     num_workers = random.choice(range(2, multiprocessing.cpu_count() * 2 + 1))
@@ -155,7 +166,8 @@ def stop_on_alarm(*args):
 
     bp = Blueprint("test_text")
     app.blueprint(bp)
-    app.run(HOST, 4121, workers=num_workers, debug=True)
+    with use_context("fork"):
+        app.run(HOST, 4121, workers=num_workers, debug=True)
 
     assert len(process_list) == num_workers + 1
 
@@ -213,6 +225,10 @@ def test_pickle_app_with_static(app, protocol):
     up_p_app.run(single_process=True)
 
 
+@pytest.mark.skipif(
+    sys.platform not in ("linux", "darwin"),
+    reason="This test requires fork context",
+)
 def test_main_process_event(app, caplog):
     # Selects a number at random so we can spot check
     num_workers = random.choice(range(2, multiprocessing.cpu_count() * 2 + 1))
@@ -235,8 +251,9 @@ def main_process_start2(app, loop):
     def main_process_stop2(app, loop):
         logger.info("main_process_stop")
 
-    with caplog.at_level(logging.INFO):
-        app.run(HOST, PORT, workers=num_workers)
+    with use_context("fork"):
+        with caplog.at_level(logging.INFO):
+            app.run(HOST, PORT, workers=num_workers)
 
     assert (
         caplog.record_tuples.count(("sanic.root", 20, "main_process_start"))

tests/test_request_stream.py

@@ -1,8 +1,5 @@
 import asyncio
 
-from contextlib import closing
-from socket import socket
-
 import pytest
 
 from sanic import Sanic
@@ -623,6 +620,4 @@ async def read_chunk():
         res = await read_chunk()
         assert res == None
 
-    # Use random port for tests
-    with closing(socket()) as sock:
-        app.run(access_log=False)
+    app.run(access_log=False, single_process=True)

tests/test_tls.py

@@ -2,6 +2,7 @@
 import os
 import ssl
 import subprocess
+import sys
 
 from contextlib import contextmanager
 from multiprocessing import Event
@@ -17,6 +18,7 @@
 
 from sanic import Sanic
 from sanic.application.constants import Mode
+from sanic.compat import use_context
 from sanic.constants import LocalCertCreator
 from sanic.exceptions import SanicException
 from sanic.helpers import _default
@@ -426,7 +428,12 @@ def stop(*args):
         app.stop()
 
     with caplog.at_level(logging.INFO):
-        app.run(host="127.0.0.1", port=42102, ssl=[localhost_dir, sanic_dir])
+        app.run(
+            host="127.0.0.1",
+            port=42102,
+            ssl=[localhost_dir, sanic_dir],
+            single_process=True,
+        )
 
     logmsg = [
         m for s, l, m in caplog.record_tuples if m.startswith("Certificate")
@@ -642,6 +649,10 @@ def test_sanic_ssl_context_create():
     assert isinstance(sanic_context, SanicSSLContext)
 
 
+@pytest.mark.skipif(
+    sys.platform not in ("linux", "darwin"),
+    reason="This test requires fork context",
+)
 def test_ssl_in_multiprocess_mode(app: Sanic, caplog):
 
     ssl_dict = {"cert": localhost_cert, "key": localhost_key}
@@ -657,8 +668,9 @@ async def shutdown(app):
         app.stop()
 
     assert not event.is_set()
-    with caplog.at_level(logging.INFO):
-        app.run(ssl=ssl_dict)
+    with use_context("fork"):
+        with caplog.at_level(logging.INFO):
+            app.run(ssl=ssl_dict)
     assert event.is_set()
 
     assert (