## derive_hub
A simple actor hub that generates the following code.
```
#[derive(::derive_builder::Builder, ::std::fmt::Debug)]
pub struct #hub_name {
#[builder(setter(skip))]
workers: ::std::vec::Vec<tokio_util::sync::CancellationToken>,
#(#field_declarations,)*
}
impl ::std::ops::Drop for #hub_name {
fn drop(&mut self) {
self.shutdown();
}
}
impl #hub_name {
/// Spawns a given number of workers threads.
///
#[inline]
pub fn spawn(&mut self, worker_count: usize) -> ::std::vec::Vec<::tokio::task::JoinHandle<()>> {
assert!(worker_count > 0, "Worker count has to be greater than zero, but got {}", worker_count);
(0..worker_count)
.map(|_| {
let token = ::tokio_util::sync::CancellationToken::new();
self.workers.push(token.clone());
let item = #item_builder::default()
#(#inits)*
.build()
.expect(concat!("Should be able to build ", stringify!(#hub_name), "."));
::tokio::spawn(async move {
item.run(token).await;
})
})
.collect::<Vec<_>>()
}
/// Shutdown hub.
///
#[inline]
pub fn shutdown(&self) {
for worker in &self.workers {
worker.cancel();
}
}
}
```
## Inert Attributes:
* #[hub(skip)] - Should be used in conjunction with default functions of the builder of the agent struct.
## Preconditions:
* Crates that have to be installed: Tikio, tokio-util, derive-builder.
* The members of the struct should be inside an Arc, which will be cloned by the hub when spawning.
* Naturally, all members have to be syn and send.
* The struct has to implemnet derive_builder::Builder
* The struct that has the derive attribute has to have a method of same signature as this example:
```
pub async fn run(self, flag: tokio_util::sync::CancellationToken) {
loop {
tokio::select! {
biased;
_ = flag.cancelled() => {
/* Wind down actor */
break;
}
item = self.foo.pop() => {
/* Do something important */
}
item = self.bar.pop() => {
/* Do something important */
}
item = self.baz.pop() => {
/* Do something important */
}
};
}
}
```
## Recommendations.
* Fields should ideally contain a deadqueue::Queue.