ASGI (Asynchronous Server Gateway Interface)¶

This chapter contains information about using ASGI with Pyramid. Read about the ASGI specification.

The example app below uses the WSGI to ASGI wrapper from the asgiref library to transform normal WSGI requests into ASGI responses. This allows the application to be run with an ASGI server, such as uvicorn or daphne.

WSGI -> ASGI application¶ This example uses the wrapper provided by asgiref to convert a WSGI application to ASGI, allowing it to be run by an ASGI server. Please note that not all extended features of WSGI may be supported, such as file handles for incoming POST bodies. # app.py from asgiref.wsgi import WsgiToAsgi from pyramid.config import Configurator from pyramid.response import Response def hello_world ( request ): return Response ( "Hello" ) # Configure a normal WSGI app then wrap it with WSGI -> ASGI class with Configurator () as config : config . add_route ( "hello" , "/" ) config . add_view ( hello_world , route_name = "hello" ) wsgi_app = config . make_wsgi_app () app = WsgiToAsgi ( wsgi_app )

Extended WSGI -> ASGI WebSocket application¶ This example extends the asgiref wrapper to enable routing ASGI consumers alongside the converted WSGI application. This is just one potential solution for routing ASGI consumers. # app.py from asgiref.wsgi import WsgiToAsgi from pyramid.config import Configurator from pyramid.response import Response class ExtendedWsgiToAsgi ( WsgiToAsgi ): """Extends the WsgiToAsgi wrapper to include an ASGI consumer protocol router""" def __init__ ( self , * args , ** kwargs ): super () . __init__ ( * args , ** kwargs ) self . protocol_router = { "http" : {}, "websocket" : {}} async def __call__ ( self , scope , * args , ** kwargs ): protocol = scope [ "type" ] path = scope [ "path" ] try : consumer = self . protocol_router [ protocol ][ path ] except KeyError : consumer = None if consumer is not None : await consumer ( scope , * args , ** kwargs ) await super () . __call__ ( scope , * args , ** kwargs ) if consumer is not None : await consumer ( scope , * args , ** kwargs ) try : await super () . __call__ ( scope , * args , ** kwargs ) except ValueError as e : # The developer may wish to improve handling of this exception. # See https://github.com/Pylons/pyramid_cookbook/issues/225 and # https://asgi.readthedocs.io/en/latest/specs/www.html#websocket pass except Exception as e : raise e def route ( self , rule , * args , ** kwargs ): try : protocol = kwargs [ "protocol" ] except KeyError : raise Exception ( "You must define a protocol type for an ASGI handler" ) def _route ( func ): self . protocol_router [ protocol ][ rule ] = func return _route HTML_BODY = """<!DOCTYPE html> <html> <head> <title>ASGI WebSocket</title> </head> <body> <h1>ASGI WebSocket Demo</h1> <form action="" onsubmit="sendMessage(event)"> <input type="text" id="messageText" autocomplete="off"/> <button>Send</button> </form> <ul id='messages'> </ul> <script> var ws = new WebSocket("ws://127.0.0.1:8000/ws"); ws.onmessage = function(event) { var messages = document.getElementById('messages') var message = document.createElement('li') var content = document.createTextNode(event.data) message.appendChild(content) messages.appendChild(message) }; function sendMessage(event) { var input = document.getElementById("messageText") ws.send(input.value) input.value = '' event.preventDefault() } </script> </body> </html> """ # Define normal WSGI views def hello_world ( request ): return Response ( HTML_BODY ) # Configure a normal WSGI app then wrap it with WSGI -> ASGI class with Configurator () as config : config . add_route ( "hello" , "/" ) config . add_view ( hello_world , route_name = "hello" ) wsgi_app = config . make_wsgi_app () app = ExtendedWsgiToAsgi ( wsgi_app ) # Define ASGI consumers @app.route ( "/ws" , protocol = "websocket" ) async def hello_websocket ( scope , receive , send ): while True : message = await receive () if message [ "type" ] == "websocket.connect" : await send ({ "type" : "websocket.accept" }) elif message [ "type" ] == "websocket.receive" : text = message . get ( "text" ) if text : await send ({ "type" : "websocket.send" , "text" : text }) else : await send ({ "type" : "websocket.send" , "bytes" : message . get ( "bytes" )}) elif message [ "type" ] == "websocket.disconnect" : break