# First Steps

The simplest FastAPI file could look like this:

```Python
{!../../../docs_src/first_steps/tutorial001.py!}
```

Copy that to a file `main.py`.

Run the live server:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>

    - istio-proxy container exists and
        - does not have DISABLE_ENVOY environment variable (which triggers proxyless mode)
        - has a istio-proxy container, with first 2 args "proxy" and "sidecar" - or less then 2 args, or first arg not proxy.
        - "sidecar.istio.io/inject" is not false
        - "sidecar.istio.io/status" exists

### Redirect API

    assertThat(c2.socket().isClosed).isFalse()

    // Add a third connection
    val c3 = factory.newConnection(pool, routeC1, 75L)

    // The third connection bounces the first.
    assertThat(pool.closeConnections(100L)).isEqualTo(0L)
    assertThat(pool.connectionCount()).isEqualTo(2)
    assertThat(c1.socket().isClosed).isTrue()
    assertThat(c2.socket().isClosed).isFalse()

This document provides an overview of the architecture and design decisions around Ztunnel, the node-proxy component in ambient mode.

## Background and motivation

Motivations to implement ztunnel generally came from two areas.

First, and most importantly, it serves as a means to implement the real goal: waypoints.
For various reasons outside the scope of this document, there is a desire to move from a sidecar based architecture to a "remote proxy" architecture.

    * This will be done by sending a POST request (from *your API*) to some *external API* provided by that external developer (this is the "callback").

## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

We may ask you to answer these questions directly in the GitHub issue or (for large changes) in a shared Google Doc.

If you are looking for good first issues, take a look at the list of [good first issues](https://github.com/gradle/gradle/labels/good%20first%20issue) that should be actionable and ready for a contribution.

### Security vulnerabilities

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# this PR, this automations will have its `if` checked to run.  In a way, the `on` conditions
# function as an implicit first `if` for every automation in the file.

# You can define multiple automations in a .cm file, but each automation name should be unique
# within the file.  We keep each automation (or very closely related group of automations) in

 * [FirDeclarationGenerationExtension][org.jetbrains.kotlin.fir.extensions.FirDeclarationGenerationExtension]s.
 *
 * [DeclarationsInPackageProvider] first tries the [FirSymbolNamesProvider] of the analysis session's underlying FIR session, because it
 * provides symbol names from binary libraries in Standalone mode, which the Standalone declaration provider does not contain (to avoid

#### `lru_cache` Technical Details

`@lru_cache` modifies the function it decorates to return the same value that was returned the first time, instead of computing it again, executing the code of the function every time.

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    ): KtCallInfo? {
        if (this is FirCheckNotNullCall)
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        if (this is FirResolvedQualifier) {