Add two new events on the reloader process (#2413)

sanic/mixins/listeners.py

@@ -17,6 +17,8 @@ class ListenerEvent(str, Enum):
     AFTER_SERVER_STOP = "server.shutdown.after"
     MAIN_PROCESS_START = auto()
     MAIN_PROCESS_STOP = auto()
+    RELOAD_PROCESS_START = auto()
+    RELOAD_PROCESS_STOP = auto()
 
 
 class ListenerMixin(metaclass=SanicMeta):
@@ -73,6 +75,16 @@ class ListenerMixin(metaclass=SanicMeta):
     ) -> ListenerType[Sanic]:
         return self.listener(listener, "main_process_stop")
 
+    def reload_process_start(
+        self, listener: ListenerType[Sanic]
+    ) -> ListenerType[Sanic]:
+        return self.listener(listener, "reload_process_start")
+
+    def reload_process_stop(
+        self, listener: ListenerType[Sanic]
+    ) -> ListenerType[Sanic]:
+        return self.listener(listener, "reload_process_stop")
+
     def before_server_start(
         self, listener: ListenerType[Sanic]
     ) -> ListenerType[Sanic]:

sanic/mixins/runner.py

@@ -11,6 +11,7 @@ from asyncio import (
     all_tasks,
     get_event_loop,
     get_running_loop,
+    new_event_loop,
 )
 from contextlib import suppress
 from functools import partial
@@ -32,6 +33,7 @@ from sanic.models.handler_types import ListenerType
 from sanic.server import Signal as ServerSignal
 from sanic.server import try_use_uvloop
 from sanic.server.async_server import AsyncioServer
+from sanic.server.events import trigger_events
 from sanic.server.protocols.http_protocol import HttpProtocol
 from sanic.server.protocols.websocket_protocol import WebSocketProtocol
 from sanic.server.runners import serve, serve_multiple, serve_single
@@ -538,15 +540,21 @@ class RunnerMixin(metaclass=SanicMeta):
             except IndexError:
                 raise RuntimeError("Did not find any applications.")
 
+        reloader_start = primary.listeners.get("reload_process_start")
+        reloader_stop = primary.listeners.get("reload_process_stop")
         # We want to run auto_reload if ANY of the applications have it enabled
         if (
             cls.should_auto_reload()
             and os.environ.get("SANIC_SERVER_RUNNING") != "true"
-        ):
+        ):  # no cov
+            loop = new_event_loop()
+            trigger_events(reloader_start, loop)
             reload_dirs: Set[Path] = primary.state.reload_dirs.union(
                 *(app.state.reload_dirs for app in apps)
             )
-            return reloader_helpers.watchdog(1.0, reload_dirs)
+            reloader_helpers.watchdog(1.0, reload_dirs)
+            trigger_events(reloader_stop, loop)
+            return
 
         # This exists primarily for unit testing
         if not primary.state.server_info:  # no cov

tests/test_reloader.py

@@ -58,6 +58,36 @@ def write_app(filename, **runargs):
     return text
 
 
+def write_listener_app(filename, **runargs):
+    start_text = secrets.token_urlsafe()
+    stop_text = secrets.token_urlsafe()
+    with open(filename, "w") as f:
+        f.write(
+            dedent(
+                f"""\
+            import os
+            from sanic import Sanic
+
+            app = Sanic(__name__)
+
+            app.route("/")(lambda x: x)
+
+            @app.reload_process_start
+            async def reload_start(*_):
+                print("reload_start", os.getpid(), {start_text!r})
+
+            @app.reload_process_stop
+            async def reload_stop(*_):
+                print("reload_stop", os.getpid(), {stop_text!r})
+
+            if __name__ == "__main__":
+                app.run(**{runargs!r})
+            """
+            )
+        )
+    return start_text, stop_text
+
+
 def write_json_config_app(filename, jsonfile, **runargs):
     with open(filename, "w") as f:
         f.write(
@@ -92,10 +122,10 @@ def write_file(filename):
     return text
 
 
-def scanner(proc):
+def scanner(proc, trigger="complete"):
     for line in proc.stdout:
         line = line.decode().strip()
-        if line.startswith("complete"):
+        if line.startswith(trigger):
             yield line
 
 
@@ -108,7 +138,7 @@ argv = dict(
         "sanic",
         "--port",
         "42204",
-        "--debug",
+        "--auto-reload",
         "reloader.app",
     ],
 )
@@ -118,7 +148,7 @@ argv = dict(
     "runargs, mode",
     [
         (dict(port=42202, auto_reload=True), "script"),
-        (dict(port=42203, debug=True), "module"),
+        (dict(port=42203, auto_reload=True), "module"),
         ({}, "sanic"),
     ],
 )
@@ -151,7 +181,7 @@ async def test_reloader_live(runargs, mode):
     "runargs, mode",
     [
         (dict(port=42302, auto_reload=True), "script"),
-        (dict(port=42303, debug=True), "module"),
+        (dict(port=42303, auto_reload=True), "module"),
         ({}, "sanic"),
     ],
 )
@@ -183,3 +213,30 @@ async def test_reloader_live_with_dir(runargs, mode):
             terminate(proc)
             with suppress(TimeoutExpired):
                 proc.wait(timeout=3)
+
+
+def test_reload_listeners():
+    with TemporaryDirectory() as tmpdir:
+        filename = os.path.join(tmpdir, "reloader.py")
+        start_text, stop_text = write_listener_app(
+            filename, port=42305, auto_reload=True
+        )
+
+        proc = Popen(
+            argv["script"], cwd=tmpdir, stdout=PIPE, creationflags=flags
+        )
+        try:
+            timeout = Timer(TIMER_DELAY, terminate, [proc])
+            timeout.start()
+            # Python apparently keeps using the old source sometimes if
+            # we don't sleep before rewrite (pycache timestamp problem?)
+            sleep(1)
+            line = scanner(proc, "reload_start")
+            assert start_text in next(line)
+            line = scanner(proc, "reload_stop")
+            assert stop_text in next(line)
+        finally:
+            timeout.cancel()
+            terminate(proc)
+            with suppress(TimeoutExpired):
+                proc.wait(timeout=3)

tests/test_server_events.py

@@ -199,3 +199,16 @@ async def test_missing_startup_raises_exception(app):
 
     with pytest.raises(SanicException):
         await srv.before_start()
+
+
+def test_reload_listeners_attached(app):
+    async def dummy(*_):
+        ...
+
+    app.reload_process_start(dummy)
+    app.reload_process_stop(dummy)
+    app.listener("reload_process_start")(dummy)
+    app.listener("reload_process_stop")(dummy)
+
+    assert len(app.listeners.get("reload_process_start")) == 2
+    assert len(app.listeners.get("reload_process_stop")) == 2