Re: Is there an interest for an async JSON-RPC library in boost ?

From: Klemens Morgenstern (klemensdavidmorgenstern_at_[hidden])
Date: 2024-04-10 22:25:07

On Thu, Apr 11, 2024 at 3:23 AM Quentin Chateau via Boost
<boost_at_[hidden]> wrote:
>
> A couple of years ago, I wrote packio, a library implementing asynchronous
> client and server for msgpack-rpc. Over time it evolved into something more
> generic, an async implementation of the JSON-RPC (https://www.jsonrpc.org/)
> spec with customizable serialization.
>
> It is built on top of asio, and boost.json is supported serializer. This
> means that with minimal efforts it could evolve into an implementation of
> JSON-RPC with no dependencies outside of boost - yet extendable.
>
> My question then is: is there an interest for it ? I'd probably need to
> invest a non trivial amount of time into making it boost-compliant and
> following up on the review process, so I'm wondering whether it is worth it
> or not.
>

I'd be interested in this library. But you're right, you're in for a
lot of work and then an intense review process.

> Note that there are two known limitations in my library:
> - No support for batch mode

May I ask if you plan to support it in the future?

> - No support for sharing a transport between a client and a server (not
> part of the spec, but requested by some users)
>
> I'm looking forward to get the community's opinion. You can check my
> library on GitHub (https://github.com/qchateau/packio). Feedback on either
> community's interest for such library, or plain comments on the library are
> welcome !

Below are my thoughts when first looking at the example code

 - can your library be used with a beast websocket?

    server->dispatcher()->add_async(
        "multiply",
        {allow_extra_arguments, "a", "b"_arg = 2},
        [&io](completion_handler complete, int a, int b) {
            // Call the completion handler later
            packio::net::post(
                io, [a, b, complete = std::move(complete)]() mutable {
                    complete(a * b);
                });
        });

Do I need to post here to avoid recursion? Is completion_handler an
alias for asio::any_completion_handler?
How do I handle errors? I.e. custom json-rpc server errors.

    server->dispatcher()->add_coro(
        "pow", io, [](int a, int b) -> packio::net::awaitable<int> {
            co_return std::pow(a, b);
        })

How do I do error handling here? Throw an exception? I would be very
much interested in system::error_code.
Also: is there anything special about this function, or is it just a
convenience to avoid writing add_async with an asio::co_spawn?

Does async_serve_forever support asio::cancellation_slot?

        std::tuple{arg("a") = 42, "b"_arg = 24},

I am not a fan of that syntax. I'd prefer {{"a", 42}, {"b", 24}}

>
> Quentin
>
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