Struct Barrier

pub struct Barrier { /* private fields */ }

Available on crate feature sync only.

A barrier enables multiple threads to synchronize the beginning of some computation.

use tokio::sync::Barrier;

use futures::future::join_all;
use std::sync::Arc;

let mut handles = Vec::with_capacity(10);
let barrier = Arc::new(Barrier::new(10));
for _ in 0..10 {
    let c = barrier.clone();
    // The same messages will be printed together.
    // You will NOT see any interleaving.
    handles.push(async move {
        println!("before wait");
        let wr = c.wait().await;
        println!("after wait");
        wr
    });
}
// Will not resolve until all "before wait" messages have been printed
let wrs = join_all(handles).await;
// Exactly one barrier will resolve as the "leader"
assert_eq!(wrs.into_iter().filter(|wr| wr.is_leader()).count(), 1);

Implementations

impl Barrier

pub fn new(n: usize) -> Barrier

Creates a new barrier that can block a given number of threads.

A barrier will block n-1 threads which call Barrier::wait and then wake up all threads at once when the nth thread calls wait.

pub async fn wait(&self) -> BarrierWaitResult

Does not resolve until all tasks have rendezvoused here.

Barriers are re-usable after all threads have rendezvoused once, and can be used continuously.

A single (arbitrary) future will receive a BarrierWaitResult that returns true from BarrierWaitResult::is_leader when returning from this function, and all other threads will receive a result that will return false from is_leader.

Trait Implementations

impl Debug for Barrier

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.