# Advanced Middleware

In the main tutorial you read how to add [Custom Middleware](../tutorial/middleware.md){.internal-link target=_blank} to your application.

And then you also read how to handle [CORS with the `CORSMiddleware`](../tutorial/cors.md){.internal-link target=_blank}.

In this section we'll see how to use other middlewares.

## Adding ASGI middlewares

## Use Case

Let's start with an example **use case** and then see how to solve it with this.

Let's imagine that you have some **machine learning models** that you want to use to handle requests. 🤖

The same models are shared among requests, so, it's not one model per request, or one per user or something similar.

## Create a task function

Create a function to be run as the background task.

It is just a standard function that can receive parameters.

It can be an `async def` or normal `def` function, **FastAPI** will know how to handle it correctly.

In this case, the task function will write to a file (simulating sending an email).

And as the write operation doesn't use `async` and `await`, we define the function with normal `def`:

If there's no `gzip` in the header, it will not try to decompress the body.

That way, the same route class can handle gzip compressed or uncompressed requests.

{* ../../docs_src/custom_request_and_route/tutorial001.py hl[8:15] *}

### Create a custom `GzipRoute` class

    if depends is not None and depends.dependency is None:
        # Copy `depends` before mutating it
        depends = copy(depends)
        depends.dependency = type_annotation

    # Handle non-param type annotations like Request
    if lenient_issubclass(
        type_annotation,
        (
            Request,
            WebSocket,
            HTTPConnection,
            Response,

If you integrate your API with an OAuth2 provider, you will be able to authenticate and come back to the API docs with the acquired credentials. And interact with it using the real OAuth2 authentication.

Swagger UI will handle it behind the scenes for you, but it needs this "redirect" helper.

///

### Create a *path operation* to test it

Now, to be able to test that everything works, create a *path operation*:

So, the thief won't be able to try to use that password in another system (as many users use the same password everywhere, this would be dangerous).

## Install `passlib`

PassLib is a great Python package to handle password hashes.

It supports many secure hashing algorithms and utilities to work with them.

The recommended algorithm is "Bcrypt".

# any Mac or Linux platform with bash 4.2+. Please take care not to modify this function
# without testing properly.
#
# This function will properly handle any type of path including those with spaces using the
# loading pattern specified by *kubectl config*.
#
# testcase: "a:b c:d"
# testcase: "a b:c d:e f"
# testcase: "a b:c:d e"
parse_KUBECONFIG () {
TMPDIR=""

layer over the underlying cluster management platform, such as Kubernetes.

Istio is composed of these components:

- **Envoy** - Sidecar proxies per microservice to handle ingress/egress traffic
   between services in the cluster and from a service to external
   services. The proxies form a _secure microservice mesh_ providing a rich

pace)||r&&r!==c.selector&&("**"!==r||!c.selector)||(p.splice(o,1),c.selector&&p.delegateCount--,f.remove&&f.remove.call(e,c));a&&!p.length&&(f.teardown&&!1!==f.teardown.call(e,h,v.handle)||ce.removeEvent(e,d,v.handle),delete u[d])}else for(d in u)ce.event.remove(e,d+t[l],n,r,!0);ce.isEmptyObject(u)&&_.remove(e,"handle events")}},dispatch:function(e){var t,n,r,i,o,a,s=new Array(arguments.length),u=ce.event.fix(e),l=(_.get(this,"events")||Object.create(null))[u.type]||[],c=ce.event.special[u.type]...