7 releases
0.2.4 | May 21, 2024 |
---|---|
0.2.3 | May 6, 2024 |
0.1.1 | May 4, 2024 |
#541 in Asynchronous
89 downloads per month
Used in asyncs
68KB
1.5K
SLoC
Spawns
Thread context task spawner for Rust to ease async runtime agnostic coding.
Motivation
Currently, Rust does not have a standard async runtime. This exposes us a dilemma to choose one and makes creating runtime agnostic library pretty hard. The most challenging thing we have to face is how to spawn task ?
spawns
proposes a thread context task spawner for Rust std
and async runtimes. Once delivered, we are able to spawn tasks in runtime agnostic manner. Together with other runtime agnostic io, timer, channel and etc. crates, we are capable to write runtime agnostic code easily.
API for async runtimes
/// Thin wrapper around task to accommodate possible new members.
#[non_exhaustive]
pub struct Task {
pub id: Id,
pub name: Name,
pub future: Box<dyn Future<Output = ()> + Send + 'static>,
}
/// Trait to spawn task.
pub trait Spawn {
fn spawn(&self, task: Task);
}
/// Scope where tasks are [spawn]ed through given [Spawn].
pub struct SpawnScope<'a> {}
/// Enters a scope where new tasks will be [spawn]ed through given [Spawn].
pub fn enter(spawner: &dyn Spawn) -> SpawnScope<'_>;
Async runtimes have to do two things to accommodate for other runtime agnostic API.
- Implements
Spawn
to spawn asynchronous task. - Calls
enter
in all executor threads.
API for clients
impl<T> JoinHandle<T> {
/// Gets id of the associated task.
pub fn id(&self) -> Id {}
/// Cancels associated task with this handle.
///
/// Cancellation is inherently concurrent with task execution. Currently, there is no guarantee
/// about promptness, the task could even run to complete normally after cancellation.
pub fn cancel(&self) { }
/// Attaches to associated task to gain cancel on [Drop] permission.
pub fn attach(self) -> TaskHandle<T> { }
}
impl<T> Future for JoinHandle<T> {
type Output = Result<T, JoinError>;
}
/// Spawns a new task.
///
/// # Panics
/// 1. Panic if no spawner.
/// 2. Panic if [Spawn::spawn] panic.
pub fn spawn<T, F>(f: F) -> JoinHandle<T>
where
F: Future<Output = T> + Send + 'static,
T: Send + 'static;
The API is capable to spawn, join and cancel tasks as what tokio
, smol
and async-std
do.
Concerns
- Boxing ? Yes, it needs
GlobalAlloc
. - Boxing even the entry future ? No, but
try_id()
will returnNone
. I guess we could provides function to wrap a bit. no_std
? No, it needsthread_local!
currently. We can move this to#[thread_local]
once stabilized.spawn_local
for!Send
future ? No, at least for now. I saw onlyasync-global-executor
is capable tospawn_local
freely. I think it is Rust's responsibility to not treat futures owning!Send
as!Send
. This way there will be little chance for us to create!Send
futures. See Async Rust needs Await and 'thread forSend
Future
for my thoughts on this. For futures that capturing!Send
in first place and storing thread local!Send
, they need current thread executor.
Packages
- spawns-core provides
Spawn
andenter()
for async runtimes to setup thread context task spawner. - spawns-compat provides compatibility for
tokio
,smol
andasync-global-executor
(which is used byasync-std
) through feature gates. - spawns-executor provides full functional
block_on
with both current thread executor and multi-thread executor. - spawns exports all above packages including feature gates
tokio
,smol
andasync-global-executor
. In addition, it provides feature gateexecutor
to includespawns-executor
.
Examples
See examples. A minimum runtime agnostic echo server is listed here for demonstration.
use async_net::*;
use futures_lite::io;
pub async fn echo_server(port: u16) {
let listener = TcpListener::bind(("127.0.0.1", port)).await.unwrap();
println!("Listen on port: {}", listener.local_addr().unwrap().port());
let mut echos = vec![];
let mut id_counter = 0;
loop {
let (stream, remote_addr) = listener.accept().await.unwrap();
id_counter += 1;
let id = id_counter;
let handle = spawns::spawn(async move {
eprintln!("{:010}[{}]: serving", id, remote_addr);
let (reader, writer) = io::split(stream);
match io::copy(reader, writer).await {
Ok(_) => eprintln!("{:010}[{}]: closed", id, remote_addr),
Err(err) => eprintln!("{:010}[{}]: {:?}", id, remote_addr, err),
}
})
.attach();
echos.push(handle);
}
}
All you have to do for it to be function is setting up thread context task spawner.
License
Dependencies
~0–9.5MB
~103K SLoC