Sharing runtime with a dynamic lib loaded at runtime.

[Kirottu]

Hello,

I would like to build a modular bot system with this library in rust, using libloading to load dynamic libraries with command groups. So far I have gotten it to the point that everything works except for the actual running of the commands. Whenever I try to run the commands from a group within a shared library it gives an error about there being no tokio runtime present.

thread '<unnamed>' panicked at 'there is no reactor running, must be called from the context of a Tokio 1.x runtime', /home/kirottu/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.15.0/src/runtime/context.rs:54:26
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

The problem is that there seems to be no obvious way to create a separate runtime for the library only or for sharing the runtime from the main bot with the library. Any help would be appreciated!

[vicky5124]

I don't know this library specifically, or how it works, but it looks like it's running the command functions in a different system thread than the one tokio is running on.

I tried looking into the issues of the library, and found these two: https://github.com/nagisa/rust_libloading/issues/81 https://github.com/nagisa/rust_libloading/issues/97 that may be useful to figure how to run async code via that library.

[Kirottu]

Well running async code would be pretty trivial, create a new runtime, make your async calls and call it a day. But the problem here is how the functions work with serenity. There is no clear way that I can see to make the function defined with serenity #[command] macro use a specified tokio runtime. I don't even know what actually calls the function and from where when the command is sent to a discord channel.

Here is the sample code for the library if it helps:

use serenity::{
    client::Context,
    framework::standard::{
        macros::{command, group},
        CommandGroup, CommandResult,
    },
    model::channel::Message,
};

#[no_mangle]
pub fn setup() -> &'static CommandGroup {
    return &GENERAL_GROUP;
}

#[group]
#[commands(ping)]
struct General;

// ----------------------
// General group commands
// ----------------------

#[command]
#[description("Ping!")]
async fn ping(ctx: &Context, msg: &Message) -> CommandResult {
    msg.reply_ping(ctx, "pong").await?;

    Ok(())
}

[vicky5124]

Sadly, you can't use the standard framework for this, as all the commands are made at compile time and stored in the framework as 'static, you will have to either use a custom framework of yours that allows this, or modify an existing framework to allow for this (poise seems like the best option for this right now)

[kangalio]

This is not really a serenity issue, rather a tokio(+libloading?) issue. The dynamically loaded library needs to have access to the spawned runtime from the parent process. Here are some pointers https://github.com/tokio-rs/tokio/issues/1964