import threading import time async def application(scope, receive, send): assert scope['type'] == 'http' headers = scope.get('headers', []) def get_header(n, v=None): for h in headers: if h[0] == n: return h[1] return v delay = float(get_header(b'x-delay', 0)) time.sleep(delay) await send( { 'type': 'http.response.start', 'status': 200, 'headers': [ (b'content-length', b'0'), (b'x-thread', str(threading.currentThread().ident).encode()), ], } )