SNI is not used because it is illegal to use IPs in SNI, and there is no other existing standard format to represent what we need to.
Additionally, using the redirection mechanism reduces the need for clients to know the destination's ztunnel address.

Below shows an example outbound request. The "target" path is what the client sends, while the "actual" path is the real network flow after redirection.

```mermaid
graph LR

## Program and Process

We will talk a lot about the running "**process**", so it's useful to have clarity about what it means, and what's the difference with the word "**program**".

### What is a Program

The word **program** is commonly used to describe many things:

* The **code** that you write, the **Python files**.

# Security Tools

When you need to declare dependencies with OAuth2 scopes you use `Security()`.

But you still need to define what is the dependable, the callable that you pass as a parameter to `Depends()` or `Security()`.

There are multiple tools that you can use to create those dependables, and they get integrated into OpenAPI so they are shown in the automatic docs UI, they can be used by automatically generated clients and SDKs, etc.

# Alternatives, Inspiration and Comparisons

What inspired **FastAPI**, how it compares to alternatives and what it learned from them.

## Intro

**FastAPI** wouldn't exist if not for the previous work of others.

There have been many tools created before that have helped inspire its creation.

[using Guava in your build]: https://github.com/google/guava/wiki/UseGuavaInYourBuild
[repackage]: https://github.com/google/guava/wiki/UseGuavaInYourBuild#what-if-i-want-to-use-beta-apis-from-a-library-that-people-use-as-a-dependency

func (e ObjectTooLarge) Error() string {
	return "size of the object greater than what is allowed(5G)"
}

// ObjectTooSmall error returned when the size of the object < what is expected.
type ObjectTooSmall GenericError

func (e ObjectTooSmall) Error() string {
	return "size of the object less than what is expected"
}

// OperationTimedOut - a timeout occurred.
type OperationTimedOut struct{}

      }

      val now = backend.nanoTime()
      var minDelayNanos = Long.MAX_VALUE
      var readyTask: Task? = null
      var multipleReadyTasks = false

      // Decide what to run. This loop's goal wants to:
      //  * Find out what this thread should do (either run a task or sleep)
      //  * Find out if there's enough work to start another thread.
      eachQueue@ for (queue in readyQueues) {

	// since the IP is normally the same), we SNAT identified host probes in the host netns to a fixed
	// APIPA/"link-local" IP.
	//
	// It doesn't matter what this IP is, so long as it's not routable and doesn't collide with anything else.
	//
	// IPv6 link local ranges are designed to be collision-resistant by default, and so probably never need to be overridden

`swagger_ui_parameters` receives a dictionary with the configurations passed to Swagger UI directly.

FastAPI converts the configurations to **JSON** to make them compatible with JavaScript, as that's what Swagger UI needs.

## Disable Syntax Highlighting

For example, you could disable syntax highlighting in Swagger UI.

Without changing the settings, syntax highlighting is enabled by default:

It is designed to be very simple to use, and to make it very easy for any developer to integrate other components with **FastAPI**.

## What is "Dependency Injection"

**"Dependency Injection"** means, in programming, that there is a way for your code (in this case, your *path operation functions*) to declare things that it requires to work and use: "dependencies".