</p>
<p align="center">
<a href="https://github.com/tiangolo/fastapi/actions?query=workflow%3ATest+event%3Apush+branch%3Amaster" target="_blank">
    <img src="https://github.com/tiangolo/fastapi/workflows/Test/badge.svg?event=push&branch=master" alt="Test">
</a>
<a href="https://codecov.io/gh/tiangolo/fastapi" target="_blank">

```

In this case, the `startup` event handler function will initialize the items "database" (just a `dict`) with some values.

You can add more than one event handler function.

And your application won't start receiving requests until all the `startup` event handlers have completed.

### `shutdown` event

To add a function that should be run when the application is shutting down, declare it with the event `"shutdown"`:

So, you will be able to see it all in the interactive API docs.

## Connect and disconnect

* Create your `FastAPI` application.
* Create event handlers to connect and disconnect from the database.

```Python hl_lines="42  45-47  50-52"
{!../../../docs_src/async_sql_databases/tutorial001.py!}
```

## Read notes

# OpenAPI Webhooks

There are cases where you want to tell your API **users** that your app could call *their* app (sending a request) with some data, normally to **notify** of some type of **event**.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

## Webhooks steps

</p>
<p align="center">
<a href="https://github.com/tiangolo/fastapi/actions?query=workflow%3ATest+event%3Apush+branch%3Amaster" target="_blank">
    <img src="https://github.com/tiangolo/fastapi/workflows/Test/badge.svg?event=push&branch=master" alt="Test">
</a>
<a href="https://coverage-badge.samuelcolvin.workers.dev/redirect/tiangolo/fastapi" target="_blank">

            - include_router
            - get
            - put
            - post
            - delete
            - options
            - head
            - patch
            - trace

            - include_router
            - get
            - put
            - post
            - delete
            - options
            - head
            - patch
            - trace
            - on_event
            - middleware

Essas funções podem ser declaradas com `async def` ou `def` normal.

### Evento `startup`

Para adicionar uma função que deve rodar antes da aplicação iniciar, declare-a com o evento `"startup"`:

```Python hl_lines="8"
{!../../../docs_src/events/tutorial001.py!}
```

Nesse caso, a função de manipulação de evento `startup` irá inicializar os itens do "banco de dados" (só um `dict`) com alguns valores.

It has:

* Seriously impressive performance.
* WebSocket support.
* In-process background tasks.
* Startup and shutdown events.
* Test client built on HTTPX.
* CORS, GZip, Static Files, Streaming responses.
* Session and Cookie support.
* 100% test coverage.
* 100% type annotated codebase.
* Few hard dependencies.

### `response_model` Priority

If you declare both a return type and a `response_model`, the `response_model` will take priority and be used by FastAPI.

This way you can add correct type annotations to your functions even when you are returning a type different than the response model, to be used by the editor and tools like mypy. And still you can have FastAPI do the data validation, documentation, etc. using the `response_model`.