Increasing memory consumption on requests exceeding max payload size

[pmajocha]

Hi,

I have a limit of 6 Mi request body size. I've noticed, that for requests coming below that limit, the memory level is steady. When I bombard the endpoint with requests of 12 Mi, the memory footprint starts increasing. It starts increasing quite rapidly, then slows down, maybe it settles on some point (after some time memory consumption stopped at 1.2Gi, while usually I have 150 Mi usage on this particular service). I tried to reproduce it locally and it behaved the same. With requests below limit it stabilized pretty quickly, but with requests above the limit it keeps increasing. The example:

async fn handler(
    _request: HttpRequest,
    _payload: Bytes,
) -> impl Responder {
    println!("handled");
    HttpResponse::BadRequest().body("ok")
}

pub async fn run() {
    HttpServer::new(move || App::new()
        .app_data(PayloadConfig::new(6 * 1024 * 1024))
        .service(web::resource("/handle").route(web::post().to(handler)))
    )
    .bind("0.0.0.0:9910")
    .unwrap()
    .run()
    .await
    .unwrap()
}

the client code

#[tokio::main]
async fn main() {
    let client = Client::new();
    let body = repeat("x").take(12 * 1024 * 1024).collect::<String>();
    let _resp = client.post("http://0.0.0.0:9910/handle")
        .body(body.clone())
        .send()
        .await;
    println!("{_resp:?}");
}

Is this expected behavior due to some caching? Can one change the behavior to free up the memory?

Thanks for responses in advance