Streaming: Actix Web Documentation

# Streaming Responses

When returning large datasets or files, loading the entire payload into memory is inefficient and dangerous. Instead, you can stream the response body.

#Returning a Stream

Actix Web accepts asynchronous streams of Bytes.

code_blocksrust

use actix_web::{get, HttpResponse, Error};
use actix_web::body::SizedStream;
use futures_util::stream;
use bytes::Bytes;

#[get("/stream")]
async fn stream_data() -> HttpResponse {
    let my_stream = stream::iter(vec![
        Ok::<_, Error>(Bytes::from_static(b"Hello ")),
        Ok::<_, Error>(Bytes::from_static(b"World!")),
    ]);
    
    HttpResponse::Ok().streaming(my_stream)
}

#Use Cases

Streaming is crucial for video/audio delivery, large CSV exports, and proxying data from other APIs or databases without buffering.

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Reference Implementation

The following code snippet demonstrates the authoritative pattern for this documentation.

src/main.rs

Edition 2024

1use actix_web::{get, App, HttpServer, HttpResponse};
2use futures_util::stream;
3use bytes::Bytes;
4use std::convert::Infallible;
5 
6#[get("/stream")]
7async fn do_stream() -> HttpResponse {
8    let chunks = vec![
9        Result::<_, Infallible>::Ok(Bytes::from("chunk1 ")),
10        Result::<_, Infallible>::Ok(Bytes::from("chunk2 ")),
11    ];
12    let stream = stream::iter(chunks);
13    
14    HttpResponse::Ok().streaming(stream)
15}
16 
17#[actix_web::main]
18async fn main() -> std::io::Result<()> {
19    HttpServer::new(|| App::new().service(do_stream))
20        .bind(("127.0.0.1", 8080))?
21        .run()
22        .await
23}

Streaming

#Returning a Stream

#Use Cases

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Reference Implementation

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