help: async

[carlocorradini]

Firstly, hdds looks awesome!. Thanks for all your work!
I'm curious whether hdds can be used with Rust's async ecosystem.
Thanks 🙌

[hdds-team]

Thanks for the kind words, glad you like it! 🙌

Short answer: HDDS doesn't have a native async API yet. The core pub/sub datapath is synchronous today - you either poll reader.take() / read(), register a DataReaderListener callback, or block on a WaitSet. A first-class async facade (async Reader/Writer, Stream-based reception, tokio::select! integration) is on the roadmap but not implemented yet, so I don't want to promise a date.

That said, you can use HDDS inside a tokio (or any async) app right now with a small bridge: the reader's on_data_available callback fans samples into a channel, which you consume as a stream. A ClosureListener helper makes it a few lines:

use std::sync::Arc;
use tokio::sync::mpsc;
use hdds::dds::listener::ClosureListener;

// Bridge the sync callback into an async channel.
let (tx, mut rx) = mpsc::unbounded_channel();
let reader = topic
.reader()
.with_listener(Arc::new(ClosureListener::new(move |s: &MyType| {
// Runs on the HDDS router thread - keep it non-blocking.
let _ = tx.send(s.clone());
})))
.build()?;

// Now consume it like any async stream:
while let Some(sample) = rx.recv().await {
// full tokio::select! / async ecosystem available here
}

Writing is even simpler - writer.write(&sample) is a fast non-blocking enqueue, safe to call directly from async code (wrap in spawn_blocking if you want to be strict). If you use a WaitSet, run its blocking wait() on a dedicated thread results into a channel the same way.

Would a documented hdds-tokio adapter crate (channel bridge + Streame meantime? Happy to prioritize that ahead of the full async facade if there's demand.

On a broader note: there's a substantial update in the pipeline focused on stability and cross-vendor interoperability hardening, plus first-class seL4 / Microkit support for safety-critical and formally-verified deployments. A proper async facade (Stream / tokio integration) is on that same roadmap. No firm date yet - I'd rather ship it right than fast - but it's actively in progress, so stay tuned. 🙌

Olivier

[carlocorradini]

Thank you very much for your answer!
I was just curious whether hdds had any plans to support async Rust, but you have already confirmed that it is on the roadmap!

Moreover, I'm curious whether you are open to contributions 🙌

[hdds-team]

Absolutely, contributions are very welcome! 🙌
Have a look at CONTRIBUTING.md - we use a simple DCO sign-off (no CLA), and everything is dual-licensed Apache-2.0 OR MIT. Bug reports, examples, docs, and features are all fair game.
If you want a concrete starting point, your own findings below (#12) would make a great first PR. Thanks for digging into HDDS!