Fixes "after_server_start" when using return_asyncio_server. (#1676)

* Fixes ability to trigger "after_server_start", "before_server_stop", "after_server_stop" server events when using app.create_server to start your own asyncio_server
See example file run_async_advanced for a full example

* Fix a missing method on AsyncServer that some tests need
Add a tiny bit more documentation in-code
Change name of AsyncServerCoro to AsyncioServer

docs/sanic/deploying.md

@@ -158,3 +158,34 @@ loop = asyncio.get_event_loop()
 task = asyncio.ensure_future(server)
 loop.run_forever()
 ```
+
+Caveat: using this method, calling `app.create_server()` will trigger "before_server_start" server events, but not
+"after_server_start", "before_server_stop", or "after_server_stop" server events.
+
+For more advanced use-cases, you can trigger these events using the AsyncioServer object, returned by awaiting
+the server task.
+
+Here is an incomplete example (please see `run_async_advanced.py` in examples for something more complete):
+
+```python
+serv_coro = app.create_server(host="0.0.0.0", port=8000, return_asyncio_server=True)
+loop = asyncio.get_event_loop()
+serv_task = asyncio.ensure_future(serv_coro, loop=loop)
+server = loop.run_until_complete(serv_task)
+server.after_start()
+try:
+    loop.run_forever()
+except KeyboardInterrupt as e:
+    loop.stop()
+finally:
+    server.before_stop()
+
+    # Wait for server to close
+    close_task = server.close()
+    loop.run_until_complete(close_task)
+
+    # Complete all tasks on the loop
+    for connection in server.connections:
+        connection.close_if_idle()
+    server.after_stop()
+```

examples/run_async_advanced.py

@@ -0,0 +1,38 @@
+from sanic import Sanic
+from sanic import response
+from signal import signal, SIGINT
+import asyncio
+import uvloop
+
+app = Sanic(__name__)
+
+@app.listener('after_server_start')
+async def after_start_test(app, loop):
+    print("Async Server Started!")
+
+@app.route("/")
+async def test(request):
+    return response.json({"answer": "42"})
+
+asyncio.set_event_loop(uvloop.new_event_loop())
+serv_coro = app.create_server(host="0.0.0.0", port=8000, return_asyncio_server=True)
+loop = asyncio.get_event_loop()
+serv_task = asyncio.ensure_future(serv_coro, loop=loop)
+signal(SIGINT, lambda s, f: loop.stop())
+server = loop.run_until_complete(serv_task)
+server.after_start()
+try:
+    loop.run_forever()
+except KeyboardInterrupt as e:
+    loop.stop()
+finally:
+    server.before_stop()
+
+    # Wait for server to close
+    close_task = server.close()
+    loop.run_until_complete(close_task)
+
+    # Complete all tasks on the loop
+    for connection in server.connections:
+        connection.close_if_idle()
+    server.after_stop()

sanic/server.py

@@ -634,6 +634,78 @@ def trigger_events(events, loop):
             loop.run_until_complete(result)
 
 
+class AsyncioServer:
+    """
+    Wraps an asyncio server with functionality that might be useful to
+    a user who needs to manage the server lifecycle manually.
+    """
+
+    __slots__ = (
+        "loop",
+        "serve_coro",
+        "_after_start",
+        "_before_stop",
+        "_after_stop",
+        "server",
+        "connections",
+    )
+
+    def __init__(
+        self,
+        loop,
+        serve_coro,
+        connections,
+        after_start,
+        before_stop,
+        after_stop,
+    ):
+        # Note, Sanic already called "before_server_start" events
+        # before this helper was even created. So we don't need it here.
+        self.loop = loop
+        self.serve_coro = serve_coro
+        self._after_start = after_start
+        self._before_stop = before_stop
+        self._after_stop = after_stop
+        self.server = None
+        self.connections = connections
+
+    def after_start(self):
+        """Trigger "after_server_start" events"""
+        trigger_events(self._after_start, self.loop)
+
+    def before_stop(self):
+        """Trigger "before_server_stop" events"""
+        trigger_events(self._before_stop, self.loop)
+
+    def after_stop(self):
+        """Trigger "after_server_stop" events"""
+        trigger_events(self._after_stop, self.loop)
+
+    def is_serving(self):
+        if self.server:
+            return self.server.is_serving()
+        return False
+
+    def wait_closed(self):
+        if self.server:
+            return self.server.wait_closed()
+
+    def close(self):
+        if self.server:
+            self.server.close()
+            coro = self.wait_closed()
+            task = asyncio.ensure_future(coro, loop=self.loop)
+            return task
+
+    def __await__(self):
+        """Starts the asyncio server, returns AsyncServerCoro"""
+        task = asyncio.ensure_future(self.serve_coro)
+        while not task.done():
+            yield
+        self.server = task.result()
+        return self
+
+
 def serve(
     host,
     port,
@@ -700,6 +772,8 @@ def serve(
     :param reuse_port: `True` for multiple workers
     :param loop: asyncio compatible event loop
     :param protocol: subclass of asyncio protocol class
+    :param run_async: bool: Do not create a new event loop for the server,
+                      and return an AsyncServer object rather than running it
     :param request_class: Request class to use
     :param access_log: disable/enable access log
     :param websocket_max_size: enforces the maximum size for
@@ -771,7 +845,14 @@ def serve(
     )
 
     if run_async:
-        return server_coroutine
+        return AsyncioServer(
+            loop,
+            server_coroutine,
+            connections,
+            after_start,
+            before_stop,
+            after_stop,
+        )
 
     trigger_events(before_start, loop)
 

tests/test_server_events.py

@@ -1,3 +1,4 @@
+import asyncio
 import signal
 
 import pytest
@@ -89,3 +90,52 @@ async def test_trigger_before_events_create_server(app):
 
     assert hasattr(app, "db")
     assert isinstance(app.db, MySanicDb)
+
+def test_create_server_trigger_events(app):
+    """Test if create_server can trigger server events"""
+
+    flag1 = False
+    flag2 = False
+    flag3 = False
+
+    async def stop(app, loop):
+        nonlocal flag1
+        flag1 = True
+        await asyncio.sleep(0.1)
+        app.stop()
+
+    async def before_stop(app, loop):
+        nonlocal flag2
+        flag2 = True
+
+    async def after_stop(app, loop):
+        nonlocal flag3
+        flag3 = True
+
+    app.listener("after_server_start")(stop)
+    app.listener("before_server_stop")(before_stop)
+    app.listener("after_server_stop")(after_stop)
+
+    loop = asyncio.get_event_loop()
+    serv_coro = app.create_server(return_asyncio_server=True)
+    serv_task = asyncio.ensure_future(serv_coro, loop=loop)
+    server = loop.run_until_complete(serv_task)
+    server.after_start()
+    try:
+        loop.run_forever()
+    except KeyboardInterrupt as e:
+        loop.stop()
+    finally:
+        # Run the on_stop function if provided
+        server.before_stop()
+
+        # Wait for server to close
+        close_task = server.close()
+        loop.run_until_complete(close_task)
+
+        # Complete all tasks on the loop
+        signal.stopped = True
+        for connection in server.connections:
+            connection.close_if_idle()
+        server.after_stop()
+    assert flag1 and flag2 and flag3