Async runtime

The async runtime lets us run Julia on a background thread, its handle lets us send tasks to this thread. We need to enable the async-rt feature to use it. Some tasks support async operations, so we'll also need an async executor. A tokio-based executor is available when the tokio-rt feature is enabled, this feature automatically enables async-rt as well.

use jlrs::prelude::*;

fn main() {
    let (async_handle, thread_handle) = Builder::new()
        .n_threads(4)
        .async_runtime(Tokio::<3>::new(false))
        .spawn()
        .expect("cannot init Julia");

    std::mem::drop(async_handle);
    thread_handle.join().expect("runtime thread panicked")
}

We've configured Julia to use 4 threads.¹ The builder is upgraded to an AsyncBuilder by providing it with the necessary configuration. Here we've configure the runtime to use the tokio-based executor without the I/O driver, and to support 3 concurrent tasks.² If you want to use this driver, enable the tokio-net feature and change the argument of Tokio::new to true.

By default, an unbounded channel is used to let the handles communicate with the runtime thread. A bounded channel can be used by calling AsyncBuilder::channel_capacity before spawning the runtime.

After spawning the runtime, we get an AsyncHandle that we can use to interact with the runtime thread and a JoinHandle to that thread. The runtime thread shuts down when all AsyncHandles have been dropped. It's also possible to manually shut down the runtime by calling AsyncHandle::close.