Body

SQS bodies are text, so a payload SQS would refuse travels base64 with a marker attribute and is decoded again on receive.

SQS takes a narrower set of characters than UTF-8 in a body. It refuses the control characters other than tab, line feed and carriage return, and the two non-characters at the end of the basic plane. A payload that is such text, a JSON document for one, travels as it is. Any other payload travels base64-encoded, with the attribute ruststream-payload-encoding set to base64: bytes that are not UTF-8, and equally valid UTF-8 with control characters, which a binary codec often emits.

The receiving side decodes the body again before the handler sees it. A handler receives the bytes the producer published, and the marker attribute never reaches its headers. The marker counts towards the ten attributes of a message, so a binary payload leaves nine for the service's own headers. SQS refuses an empty body, and so does the in-process account.

A handler that reads the bytes itself takes a #[derive(Deserialized)] newtype over &[u8], and no codec runs. The type borrows the delivery's buffer, so nothing is copied.

Example

The handler stores thumbnails, raw image bytes that SQS would not take as text.

Macros
Manual

examples/sqs_delivery_body.rs
/// A thumbnail as the producer sent it: raw image bytes, read without a codec.
#[derive(Deserialized)]
struct Thumbnail<'a>(&'a [u8]);

#[subscriber(SqsQueue)]
async fn store(thumbnail: &Thumbnail<'_>) -> HandlerOutcome {
    tracing::info!(bytes = thumbnail.0.len(), "thumbnail stored");
    HandlerOutcome::ack()
}

examples/manual/sqs_delivery_body.rs
/// A thumbnail as the producer sent it: raw image bytes, read without a codec.
struct Thumbnail<'a>(&'a [u8]);

impl Deserialized for Thumbnail<'_> {
    type Output<'a> = Thumbnail<'a>;
    type Error = Infallible;

    fn from_payload(payload: &[u8]) -> Result<Thumbnail<'_>, Self::Error> {
        Ok(Thumbnail(payload))
    }
}

// Routes the type onto the lane of payloads that read themselves.
impl Input for Thumbnail<'_> {
    type Axis = SoloDeserialized<Thumbnail<'static>>;
}

struct Store;

// For every lifetime of the payload it borrows.
impl<'p> Handle<Thumbnail<'p>> for Store {
    fn handle(
        &self,
        thumbnail: &Thumbnail<'p>,
        _outs: &(),
        _ctx: &mut Context<'_>,
    ) -> impl Future<Output = Result<(), HandlerOutcome>> {
        tracing::info!(bytes = thumbnail.0.len(), "thumbnail stored");
        ready(Ok(()))
    }
}

Example​

Example