新增于 FastAPI 0.134.0。

///

## 什么是流 { #what-is-a-stream }

“流式传输”数据意味着你的应用会在整段数据全部准备好之前，就开始把每个数据项发送给客户端。

也就是说，它会先发送第一个数据项，客户端会接收并开始处理它，而此时你的应用可能还在生成下一个数据项。

```mermaid
sequenceDiagram
    participant App
    participant Client

    App->>App: Produce Item 1
    App->>Client: Send Item 1
    App->>App: Produce Item 2
    Client->>Client: Process Item 1
    App->>Client: Send Item 2
    App->>App: Produce Item 3

データを**ストリーミング**するとは、アイテムの全シーケンスが用意できるのを待たずに、アプリがデータアイテムの送信をクライアントに対して開始することを意味します。

つまり、最初のアイテムを送信し、クライアントはそれを受け取って処理を始めます。その間に、次のアイテムをまだ生成しているかもしれません。

```mermaid
sequenceDiagram
    participant App
    participant Client

    App->>App: Produce Item 1
    App->>Client: Send Item 1
    App->>App: Produce Item 2
    Client->>Client: Process Item 1
    App->>Client: Send Item 2
    App->>App: Produce Item 3

```Python
@lru_cache
def say_hi(name: str, salutation: str = "Ms."):
    return f"Hello {salutation} {name}"
```

你的程式可能會這樣執行：

```mermaid
sequenceDiagram

participant code as Code
participant function as say_hi()
participant execute as Execute function

    rect rgba(0, 255, 0, .1)
        code ->> function: say_hi(name="Camila")
        function ->> execute: execute function code

def say_hi(name: str, salutation: str = "Ms."):
    return f"Hello {salutation} {name}"
```

your program could execute like this:

```mermaid
sequenceDiagram

participant code as Code
participant function as say_hi()
participant execute as Execute function

    rect rgba(0, 255, 0, .1)
        code ->> function: say_hi(name="Camila")
        function ->> execute: execute function code

```Python
@lru_cache
def say_hi(name: str, salutation: str = "Ms."):
    return f"Hello {salutation} {name}"
```

プログラムは次のように実行されます:

```mermaid
sequenceDiagram

participant code as Code
participant function as say_hi()
participant execute as Execute function

    rect rgba(0, 255, 0, .1)
        code ->> function: say_hi(name="Camila")
        function ->> execute: execute function code

///

### 프록시 전달 헤더가 동작하는 방식 { #how-proxy-forwarded-headers-work }

다음은 **프록시**가 클라이언트와 **애플리케이션 서버** 사이에서 전달 헤더를 추가하는 과정을 시각적으로 나타낸 것입니다:

```mermaid
sequenceDiagram
    participant Client
    participant Proxy as Proxy/Load Balancer
    participant Server as FastAPI Server

    Client->>Proxy: HTTPS Request<br/>Host: mysuperapp.com<br/>Path: /items

    Note over Proxy: Proxy adds forwarded headers

```Python
@lru_cache
def say_hi(name: str, salutation: str = "Ms."):
    return f"Hello {salutation} {name}"
```

你的程序可能会像这样执行：

```mermaid
sequenceDiagram

participant code as Code
participant function as say_hi()
participant execute as Execute function

    rect rgba(0, 255, 0, .1)
        code ->> function: say_hi(name="Camila")
        function ->> execute: 执行函数代码
        execute ->> code: 返回结果

Diversity Statement
-------------------

We encourage everyone to participate and are committed to building a community for all. Although we
may not be able to satisfy everyone, we all agree that everyone is equal.

Whenever a participant has made a mistake, we expect them to take responsibility for it. If someone
has been harmed or offended, it is our responsibility to listen carefully and respectfully, and do
our best to right the wrong.

Here's a visual representation of how the **proxy** adds forwarded headers between the client and the **application server**:

```mermaid
sequenceDiagram
    participant Client
    participant Proxy as Proxy/Load Balancer
    participant Server as FastAPI Server

    Client->>Proxy: HTTPS Request<br/>Host: mysuperapp.com<br/>Path: /items

    Note over Proxy: Proxy adds forwarded headers

///

### 代理转发请求头如何工作 { #how-proxy-forwarded-headers-work }

下面是一个可视化图示，展示了**代理**如何在客户端与**应用服务器**之间添加转发请求头：

```mermaid
sequenceDiagram
    participant Client
    participant Proxy as Proxy/Load Balancer
    participant Server as FastAPI Server

    Client->>Proxy: HTTPS Request<br/>Host: mysuperapp.com<br/>Path: /items

    Note over Proxy: Proxy adds forwarded headers