Using capnp-rpc client in multi-threaded tokio

[juchiast]

My setup is:

interface CommandContext {
    data @0 () -> (data: Data);
}

interface CommandFactory {
    init @0 (name: Text, nd: Data) -> (cmd: CommandTrait);

    allAvailables @1 () -> (availables: Data);
}

interface CommandTrait {
    run @0 (ctx: CommandContext, inputs: Data) -> (output: Data);
}

I have 1 or more CommandFactory clients, calling them to initialize commands on remote servers. because capnp-rpc clients are not Send, I cannot send the clients to another thread, the CommandFactory and CommandTrait clients all need to stay in the same thread, so either:

• the entire app need to be rewritten using tokio LocalSet and current_thread tokio runtime
• I have to keep all capnp-rpc types in a separate tokio runtime, and communicate with them via channels

This seems like a huge limitation, am I missing something? Is there any workaround?

[juchiast]

Another use-case is using capnp-rpc client in iroh, to build a ProtocolHandler with capnp-rpc client, it need to be Send + Sync.

[isitreallyalive]

I'd also love to see multi-threaded tokio supported if it isn't already!

[stevefan1999-personal]

I also want this feature because I want to use it for a gRPC replacement but the lack of multi-thread (or explicitly requring !Send) is kind of backing me off. I can sure use tokio with the current_thread flavor but that means I cannot use, and the best thing I can do is to pass it to an async channel and hope for a valid response.

[juchiast]

The whole codebase is filled with Rc and other non-threadsafe types so this is very hard to solve, would love to hear what the maintainers think about this?