How to convert Multipart to Stream?

[oovm]

I'm developing a file forwarding function that accepts a Multipart from poem and sends a new Multipart via reqwest.

This is the current implementation:

pub async fn upload_file(mut multipart: Multipart) -> Result<StatusCode, poem::Error> {
    let mut file = None;
    while let Some(field) = multipart.next_field().await? {
        let name = field.name().unwrap_or_default();
        match name {
            "file" => {
                file = Some(field.bytes().await?);
            }
            _ => {}
        }
    }

    if let Some(file) = file {
        let resp = reqwest::Client::new()
            .post("https://dashscope.aliyuncs.com/compatible-mode/v1/files")
            .bearer_auth(&"SECRET")
            .multipart(reqwest::multipart::Form::new().text("purpose", "file-extract").part("file", Part::bytes(file)))
            .send()
            .await
            .map_err(|e| poem::Error::new(e, StatusCode::BAD_REQUEST))?;
        Ok(resp.status())
    }
    else {
        Err(poem::Error::from_string("Missing file", StatusCode::BAD_REQUEST))
    }
}

It works fine, but when a lot of users upload at the same time, the server runs out of memory,

I want to change to streaming input and streaming output.

The problem I'm having is that poem returns an AsyncRead, but reqwest expects a Stream, and I don't know how to convert that.

pub async fn upload_file_stream(mut multipart: Multipart) -> Result<StatusCode, poem::Error> {
    let mut file = None;
    let mut file_name = String::new();
    while let Some(field) = multipart.next_field().await? {
        let name = field.name().unwrap_or_default();
        match name {
            "file" => {
                file = Some(field.into_async_read());   // <--------------- change input here
            }
            "name" => {
                file_name = field.text().await?;
            }
            _ => {}
        }
    }

    if let Some(file) = file {
        let body = reqwest::Body::wrap_stream(file); // <------------ not work here
        let reader = reqwest::multipart::Part::stream(body).file_name(file_name);
        let resp = reqwest::Client::new()
            .post("https://dashscope.aliyuncs.com/compatible-mode/v1/files")
            .bearer_auth(&"SECRET")
            .multipart(reqwest::multipart::Form::new().text("purpose", "file-extract").part("file", Part::bytes(file)))
            .send()
            .await
            .map_err(|e| poem::Error::new(e, StatusCode::BAD_REQUEST))?;
        Ok(resp.status())
    }
    else {
        Err(poem::Error::from_string("Missing file", StatusCode::BAD_REQUEST))
    }
}