Middleware

Middleware is a chain of functions terminated by a callback.

It can be used to add content to the request and response or to control the calling of subsequent handlers.

A middleware callback is an async function with the following prototype.

status, headers, content, pushes = await fn(scope, info, matches, content, callback)

This is the same as an HTTP handler, with the addition of the callback which is either another middleware callback or an HTTP handler.

Simple Example

Here is a simple middleware example.

import uvicorn
from bareasgi import Application, text_writer

async def first_middleware(scope, info, matches, content, handler):
    info['message'] = 'This is first the middleware. '
    response = await handler(scope, info, matches, content)
    return response


async def second_middleware(scope, info, matches, content, handler):
    info['message'] += 'This is the second middleware.'
    response = await handler(scope, info, matches, content)
    return response


async def http_request_callback(scope, info, matches, content):
    return 200, [(b'content-type', b'text/plain')], text_writer(info['message'])


app = Application(middlewares=[first_middleware, second_middleware])
app.http_router.add({'GET'}, '/test', http_request_callback)

uvicorn.run(app, port=9009)