Streaming

Use gluegun/request when the request body is produced in chunks.

Start with request.headers, send zero or more chunks with fin.NoFin, and complete the body with fin.Fin.

import gluegun/connection
import gluegun/fin
import gluegun/message
import gluegun/request

pub fn upload_chunks(conn) {
  let timeout = connection.Milliseconds(5000)

  let assert Ok(stream) =
    request.headers(
      conn,
      request.Post,
      "/upload",
      [#("content-type", "text/plain")],
      request.options(),
    )

  let assert Ok(Nil) = request.data(conn, stream, fin.NoFin, <<"first ":utf8>>)
  let assert Ok(Nil) = request.data(conn, stream, fin.Fin, <<"last":utf8>>)

  let assert Ok(message.Response(response_fin, _status, _headers)) =
    await_final_response(conn, stream, timeout)

  case response_fin {
    fin.Fin -> <<>>
    fin.NoFin -> {
      let assert Ok(body) = message.await_body(conn, stream, timeout)
      body
    }
  }
}

fn await_final_response(conn, stream, timeout) {
  case message.await(conn, stream, timeout) {
    Ok(message.Inform(_status, _headers)) ->
      await_final_response(conn, stream, timeout)
    other -> other
  }
}

Consuming response chunks

If you need response chunks or trailers as they arrive, continue awaiting message.Data and message.Trailers with message.await instead of collecting the full body with message.await_body.

Servers may send one or more message.Inform values before the final message.Response. Skip or record those informational responses before collecting the response body. HTTP/2 servers can also send message.Push values, and upgrade flows can produce message.Upgrade or message.WebSocket values that the high-level client helpers intentionally reject.

Stream control

Streaming APIs are also the right place for request control:

• Use request.cancel(conn, stream) to cancel a request stream.
• Use request.update_flow(conn, stream, increment) when your application manages flow-control allowance directly. The increment must be positive.
• Use request.flush(conn) to flush queued Gun messages for a connection.

See the request reference and message reference for the complete streaming API.