websockets Q's: attaching an async stream, and map_err woes

[bburdette]

async stream connection

I'm attempting to connect an async stream to a websocket to write some records. In my server, where the records originate, I see printlns for all the records. But nothing is reaching the client.

I'm using add_stream to connect my stream. Any hints? Maybe add_stream doesn't do what I think it does, which is write the stream contents to the socket.

I got it to work before with a non-async function. But that one appears to read in all the records before anything is written to the websocket. I'd rather read the records lazily as they are needed.

error mapping

Maybe more of a stream question than an actix-web question. My async stream function initially has my app's error type zkerr::Error. That's convenient because I can use ? in that function. But to pass to add_stream I need a ws::ProtocolError type. I'm just making a nonsense error there. I'd like to pass in my actual error but map_err seems unaware of the type of the original error. Or something. Anyway I can't even log the error because no type. Hints welcome! The error I get on uncommmenting the logging code:

error[E0277]: `<impl TryStream<Ok = actix_web_actors::ws::Message> + futures_util::Stream<Item = Result<actix_web_actors::ws::Message, error::Error>> + 'static as TryStream>::Error` doesn't implement `std::fmt::Debug`
   --> server-lib/src/websocket.rs:114:31
    |
114 |           info!("errah {:?}", x);
    |                               ^ `<impl TryStream<Ok = actix_web_actors::ws::Message> + futures_util::Stream<Item = Result<actix_web_actors::ws::Message, error::Error>> + 'static as TryStream>::Error` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
    |
    = help: the trait `std::fmt::Debug` is not implemented for `<impl TryStream<Ok = actix_web_actors::ws::Message> + futures_util::Stream<Item = Result<actix_web_actors::ws::Message, error::Error>> + 'static as TryStream>::Error`
    = note: this error originates in the macro `$crate::__private_api::format_args` which comes from the expansion of the macro `info` (in Nightly builds, run with -Z macro-backtrace for more info)

[bburdette]

Haha, argh I just figured out where the records go. Into the StreamHandler for my StreamingWebSocket class. I was expecting that to only get messages from the client. So I guess I could parse the incoming records and see if they are supposed to go to the client or if they are FROM the client. This seems suboptimal.

[bburdette]

Maybe the way forward is to dole out the records from the async stream one at a time, and after each one wait for an ack from the client. I expect that would be considerably slower than spewing all the records without waiting though.

[bburdette]

FWIW I went back to http streaming for now; figured out a way to do what I wanted without needing bidirectional comms. So far working well.