It is quite an extensive specification and covers several complex use cases.

It includes ways to authenticate using a "third party".

That's what all the systems with "login with Facebook, Google, Twitter, GitHub" use underneath.

### OAuth 1

There was an OAuth 1, which is very different from OAuth2, and more complex, as it included direct specifications on how to encrypt the communication.

It is not very popular or used nowadays.

But there are situations where you might need to access the `Request` object directly.

## Details about the `Request` object

As **FastAPI** is actually **Starlette** underneath, with a layer of several tools on top, you can use Starlette's <a href="https://www.starlette.io/requests/" class="external-link" target="_blank">`Request`</a> object directly when you need to.

## HTTPX

Even if your **FastAPI** application uses normal `def` functions instead of `async def`, it is still an `async` application underneath.

func unwrapErrs(err error) (leafErr error) {
	uerr := errors.Unwrap(err)
	depth := 1
	for uerr != nil {
		// Save the current `uerr`
		leafErr = uerr
		// continue to look for leaf errors underneath
		uerr = errors.Unwrap(leafErr)
		depth++
		if depth == unwrapErrsDepth {
			// If we have reached enough depth we
			// do not further recurse down, this
			// is done to avoid any unnecessary

In the chapters about security, there are utility functions that are implemented in this same way.

If you understood all this, you already know how those utility tools for security work underneath.

		return http.ErrServerClosed
	}
	srv.listenerMutex.Unlock()

	if atomic.AddUint32(&srv.inShutdown, 1) > 1 {
		// shutdown in progress
		return http.ErrServerClosed
	}

	// Close underneath HTTP listener.
	srv.listenerMutex.Lock()
	err := srv.listener.Close()
	srv.listenerMutex.Unlock()
	if err != nil {
		return err
	}

	// Wait for opened connection to be closed up to Shutdown timeout.

And of course, it supports the same:

* data validation
* data serialization
* data documentation, etc.

This works the same way as with Pydantic models. And it is actually achieved in the same way underneath, using Pydantic.

/// info

Keep in mind that dataclasses can't do everything Pydantic models can do.

So, you might still need to use Pydantic models.

				// been seen recently due to hardware issues
				// causes Reads() to go slower than Writes().
				//
				// Send such results anyways as this shall
				// expose a problem underneath.
				if totalPut > throughputHighestPut {
					throughputHighestResults = results
					throughputHighestPut = totalPut
					// let the client see lower value as well
					throughputHighestGet = totalGet
				}

	select {
	case result, ok := <-listener.acceptCh:
		if ok {
			return result.conn, result.err
		}
	case <-listener.ctx.Done():
	}
	return nil, syscall.EINVAL
}

// Close - closes underneath all TCP listeners.
func (listener *httpListener) Close() (err error) {
	listener.ctxCanceler()

	for i := range listener.listeners {
		listener.listeners[i].Close()
	}

	return nil
}

Because of that, it's now recommended to instead use the `lifespan` as explained above.

## Technical Details

Just a technical detail for the curious nerds. 🤓

Underneath, in the ASGI technical specification, this is part of the <a href="https://asgi.readthedocs.io/en/latest/specs/lifespan.html" class="external-link" target="_blank">Lifespan Protocol</a>, and it defines events called `startup` and `shutdown`.