# Response Headers

## Use a `Response` parameter

You can declare a parameter of type `Response` in your *path operation function* (as you can do for cookies).

And then you can set headers in that *temporal* response object.

```Python hl_lines="1  7-8"
{!../../../docs_src/response_headers/tutorial002.py!}
```

And then you can return any object you need, as you normally would (a `dict`, a database model, etc).

You can return a `RedirectResponse` directly:

```Python hl_lines="2  9"
{!../../../docs_src/custom_response/tutorial006.py!}
```

---

Or you can use it in the `response_class` parameter:


```Python hl_lines="2  7  9"
{!../../../docs_src/custom_response/tutorial006b.py!}
```

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

For many scenarios, you can handle security (authorization, authentication, etc.) with dependencies, using `Depends()`.

But when you want to also declare OAuth2 scopes, you can use `Security()` instead of `Depends()`.

    // Running at time 50, the pool returns that nothing can be evicted until time 150.
    assertThat(pool.closeConnections(50L)).isEqualTo(100L)
    assertThat(pool.connectionCount()).isEqualTo(1)
    assertThat(c1.socket().isClosed).isFalse()

    // Running at time 60, the pool returns that nothing can be evicted until time 150.
    assertThat(pool.closeConnections(60L)).isEqualTo(90L)

  //
  // List/watch requests for CertificateSigningRequests can filter on this field using a "spec.signerName=NAME" fieldSelector.
  //
  // Well-known Kubernetes signers are:
  //  1. "kubernetes.io/kube-apiserver-client": issues client certificates that can be used to authenticate to kube-apiserver.
  //   Requests for this signer are never auto-approved by kube-controller-manager, can be issued by the "csrsigning" controller in kube-controller-manager.

The `TestClient` is based on <a href="https://www.python-httpx.org" class="external-link" target="_blank">HTTPX</a>, and luckily, we can use it directly to test the API.

## Example

### Concurrency + Parallelism: Web + Machine Learning

With **FastAPI** you can take the advantage of concurrency that is very common for web development (the same main attraction of NodeJS).

But you can also exploit the benefits of parallelism and multiprocessing (having multiple processes running in parallel) for **CPU bound** workloads like those in Machine Learning systems.

    once you get into the running container so `bazel` can find the `tensorflow`
    workspace).

    you can do this by using the following command. As an example-

    ```bash
    docker run -it --rm -v $PWD:/tmp -w /tmp tensorflow/build:2.15-python3.10
    ```

    Once you have the packages installed, you can run a specific unit test in
    bazel by doing as follows:

    ```bash

## Develop and verify

After you make a change, you can run `mvn clean teamcity-configs:generate` to generate and verify the generated TeamCity configuration XMLs.

You also need to run `mvn clean verify` with Java 8 before committing changes.

If you have ktlint errors, you can automatically fix them by running `mvn com.github.gantsign.maven:ktlint-maven-plugin:1.1.1:format`.

## Why distributed MinIO?

MinIO in distributed mode can help you setup a highly-available storage system with a single object storage deployment. With distributed MinIO, you can optimally use storage devices, irrespective of their location in a network.

### Data protection