Add ASGI documentation

docs/sanic/deploying.md

@@ -1,7 +1,12 @@
 # Deploying
 
-Deploying Sanic is made simple by the inbuilt webserver. After defining an
-instance of `sanic.Sanic`, we can call the `run` method with the following
+Deploying Sanic is very simple using one of three options: the inbuilt webserver,
+an [ASGI webserver](https://asgi.readthedocs.io/en/latest/implementations.html), or `gunicorn`.
+It is also very common to place Sanic behind a reverse proxy, like `nginx`. 
+
+## Running via Sanic webserver
+
+After defining an instance of `sanic.Sanic`, we can call the `run` method with the following
 keyword arguments:
 
 - `host` *(default `"127.0.0.1"`)*: Address to host the server on.
@@ -17,7 +22,13 @@ keyword arguments:
   [asyncio.protocol](https://docs.python.org/3/library/asyncio-protocol.html#protocol-classes).
 - `access_log` *(default `True`)*: Enables log on handling requests (significantly slows server).
 
-## Workers
+```python
+app.run(host='0.0.0.0', port=1337, access_log=False)
+```
+
+In the above example, we decided to turn off the access log in order to increase performance.
+
+### Workers
 
 By default, Sanic listens in the main process using only one CPU core. To crank
 up the juice, just specify the number of workers in the `run` arguments.
@@ -29,9 +40,9 @@ app.run(host='0.0.0.0', port=1337, workers=4)
 Sanic will automatically spin up multiple processes and route traffic between
 them. We recommend as many workers as you have available cores.
 
-## Running via command
+### Running via command
 
-If you like using command line arguments, you can launch a Sanic server by
+If you like using command line arguments, you can launch a Sanic webserver by
 executing the module. For example, if you initialized Sanic as `app` in a file
 named `server.py`, you could run the server like so:
 
@@ -46,6 +57,33 @@ if __name__ == '__main__':
     app.run(host='0.0.0.0', port=1337, workers=4)
 ```
 
+## Running via ASGI
+
+Sanic is also ASGI-compliant. This means you can use your preferred ASGI webserver
+to run Sanic. The three main implementations of ASGI are
+[Daphne](http://github.com/django/daphne), [Uvicorn](https://www.uvicorn.org/),
+and [Hypercorn](https://pgjones.gitlab.io/hypercorn/index.html).
+
+Follow their documentation for the proper way to run them, but it should look
+something like:
+
+```
+daphne myapp:app
+uvicorn myapp:app
+hypercorn myapp:app
+```
+
+A couple things to note when using ASGI:
+
+1. When using the Sanic webserver, websockets will run using the [`websockets`](https://websockets.readthedocs.io/) package. In ASGI mode, there is no need for this package since websockets are managed in the ASGI server.
+1. The ASGI [lifespan protocol](https://asgi.readthedocs.io/en/latest/specs/lifespan.html) supports
+only two server events: startup and shutdown. Sanic has four: before startup, after startup, 
+before shutdown, and after shutdown. Therefore, in ASGI mode, the startup and shutdown events will 
+run consecutively and not actually around the server process beginning and ending (since that 
+is now controlled by the ASGI server). Therefore, it is best to use `after_server_start` and 
+`before_server_stop`.
+1. ASGI mode is still in "beta" as of Sanic v19.6.
+
 ## Running via Gunicorn
 
 [Gunicorn](http://gunicorn.org/) ‘Green Unicorn’ is a WSGI HTTP Server for UNIX.
@@ -64,7 +102,9 @@ of the memory leak.
 
 See the [Gunicorn Docs](http://docs.gunicorn.org/en/latest/settings.html#max-requests) for more information.
 
-## Running behind a reverse proxy
+## Other deployment considerations
+
+### Running behind a reverse proxy
 
 Sanic can be used with a reverse proxy (e.g. nginx). There's a simple example of nginx configuration:
 
@@ -84,7 +124,7 @@ server {
 
 If you want to get real client ip, you should configure `X-Real-IP` and `X-Forwarded-For` HTTP headers and set `app.config.PROXIES_COUNT` to `1`; see the configuration page for more information.
 
-## Disable debug logging
+### Disable debug logging for performance
 
 To improve the performance add `debug=False` and `access_log=False` in the `run` arguments.
 
@@ -104,9 +144,10 @@ Or you can rewrite app config directly
 app.config.ACCESS_LOG = False
 ```
 
-## Asynchronous support
-This is suitable if you *need* to share the sanic process with other applications, in particular the `loop`.
-However be advised that this method does not support using multiple processes, and is not the preferred way
+### Asynchronous support and sharing the loop
+
+This is suitable if you *need* to share the Sanic process with other applications, in particular the `loop`.
+However, be advised that this method does not support using multiple processes, and is not the preferred way
 to run the app in general.
 
 Here is an incomplete example (please see `run_async.py` in examples for something more practical):

sanic/app.py

@@ -1393,6 +1393,9 @@ class Sanic:
     # -------------------------------------------------------------------- #
 
     async def __call__(self, scope, receive, send):
+        """To be ASGI compliant, our instance must be a callable that accepts
+        three arguments: scope, receive, send. See the ASGI reference for more
+        details: https://asgi.readthedocs.io/en/latest/"""
         self.asgi = True
         asgi_app = await ASGIApp.create(self, scope, receive, send)
         await asgi_app()

sanic/asgi.py

@@ -260,7 +260,6 @@ class ASGIApp:
             message = await self.transport.receive()
             chunk = message.get("body", b"")
             await self.request.stream.put(chunk)
-            # self.sanic_app.loop.create_task(self.request.stream.put(chunk))
 
             more_body = message.get("more_body", False)
 
@@ -288,7 +287,6 @@ class ASGIApp:
             headers = [
                 (str(name).encode("latin-1"), str(value).encode("latin-1"))
                 for name, value in response.headers.items()
-                # if name not in ("Set-Cookie",)
             ]
         except AttributeError:
             logger.error(

sanic/testing.py

@@ -183,6 +183,14 @@ class SanicASGIAdapter(requests.asgi.ASGIAdapter):
         *args: typing.Any,
         **kwargs: typing.Any,
     ) -> requests.Response:
+        """This method is taken MOSTLY verbatim from requests-asyn. The
+        difference is the capturing of a response on the ASGI call and then
+        returning it on the response object. This is implemented to achieve:
+
+        request, response = await app.asgi_client.get("/")
+
+        You can see the original code here:
+        https://github.com/encode/requests-async/blob/614f40f77f19e6c6da8a212ae799107b0384dbf9/requests_async/asgi.py#L51"""  # noqa
         scheme, netloc, path, query, fragment = urlsplit(
             request.url
         )  # type: ignore
@@ -345,9 +353,6 @@ class SanicASGITestClient(requests.ASGISession):
         self.app = app
         self.base_url = base_url
 
-    # async def send(self, prepared_request, *args, **kwargs):
-    #     return await super().send(*args, **kwargs)
-
     async def request(self, method, url, gather_request=True, *args, **kwargs):
         self.gather_request = gather_request
         print(url)