16 releases (7 stable)
2.0.1 | Mar 24, 2024 |
---|---|
2.0.0 | Oct 19, 2023 |
1.2.0 | Mar 27, 2023 |
0.15.4 | Feb 20, 2023 |
0.3.0 |
|
#170 in Concurrency
445 downloads per month
Used in 4 crates
(3 directly)
19KB
332 lines
Async Local
Unlocking the potential of thread-locals in an async context
This crate enables references to thread locals to be used in an async context and accross await points or within blocking threads managed by the Tokio runtime
How it works
By using a barrier to rendezvous worker threads during runtime shutdown, it can be gauranteed that no task will outlive thread local data belonging to worker threads. With this, pointers to thread locals constrained by invariant lifetimes are guaranteed to be of a valid lifetime suitable for use accross await points.
Runtime Configuration (optional)
For best performance, use the Tokio runtime as configured via the tokio::main or tokio::test macro with the crate
attribute set to async_local
while the barrier-protected-runtime
feature is enabled on async-local
. Doing so configures the Tokio runtime with a barrier that rendezvous runtime worker threads during shutdown in a way that ensures tasks never outlive thread local data owned by runtime worker threads and obviates the need for Box::leak as a fallback means of lifetime extension.
#[cfg(test)]*
mod tests {
use std::sync::atomic::{AtomicUsize, Ordering};
use async_local::{AsyncLocal, Context};
use generativity::make_guard;
use tokio::task::yield_now;
thread_local! {
static COUNTER: Context<AtomicUsize> = Context::new(AtomicUsize::new(0));
}
#[tokio::test(crate = "async_local", flavor = "multi_thread")]
async fn it_increments() {
make_guard!(guard);
let counter = COUNTER.local_ref(guard);
yield_now().await;
counter.fetch_add(1, Ordering::SeqCst);
}
}
Dependencies
~0.3–25MB
~366K SLoC