Struct tokio::task::JoinSet

source · [−]

pub struct JoinSet<T> { /* private fields */ }

Expand description

A collection of tasks spawned on a Tokio runtime.

A JoinSet can be used to await the completion of some or all of the tasks in the set. The set is not ordered, and the tasks will be returned in the order they complete.

All of the tasks must have the same return type T.

When the JoinSet is dropped, all tasks in the JoinSet are immediately aborted.

Examples

Spawn multiple tasks and wait for them.

use tokio::task::JoinSet;

#[tokio::main]
async fn main() {
    let mut set = JoinSet::new();

    for i in 0..10 {
        set.spawn(async move { i });
    }

    let mut seen = [false; 10];
    while let Some(res) = set.join_next().await {
        let idx = res.unwrap();
        seen[idx] = true;
    }

    for i in 0..10 {
        assert!(seen[i]);
    }
}

Implementations

source

impl<T> JoinSet<T>

source

pub fn new() -> Self

Create a new JoinSet.

source

pub fn len(&self) -> usize

Returns the number of tasks currently in the JoinSet.

source

pub fn is_empty(&self) -> bool

Returns whether the JoinSet is empty.

source

impl<T: 'static> JoinSet<T>

source

pub fn spawn<F>(&mut self, task: F) -> AbortHandle where
 F: Future<Output = T>,
 F: Send + 'static,
 T: Send,

Spawn the provided task on the JoinSet, returning an AbortHandle that can be used to remotely cancel the task.

Panics

This method panics if called outside of a Tokio runtime.

source

pub fn spawn_on<F>(&mut self, task: F, handle: &Handle) -> AbortHandle where
 F: Future<Output = T>,
 F: Send + 'static,
 T: Send,

Spawn the provided task on the provided runtime and store it in this JoinSet returning an AbortHandle that can be used to remotely cancel the task.

source

pub fn spawn_local<F>(&mut self, task: F) -> AbortHandle where
F: Future<Output = T>,
F: 'static,

Spawn the provided task on the current LocalSet and store it in this JoinSet, returning an AbortHandle that can be used to remotely cancel the task.

Panics

This method panics if it is called outside of a LocalSet.

source

pub fn spawn_local_on<F>(
 &mut self,
 task: F,
 local_set: &LocalSet
) -> AbortHandle where
 F: Future<Output = T>,
 F: 'static,

Spawn the provided task on the provided LocalSet and store it in this JoinSet, returning an AbortHandle that can be used to remotely cancel the task.

source

pub async fn join_next(&mut self) -> Option<Result<T, JoinError>>

Waits until one of the tasks in the set completes and returns its output.

Returns None if the set is empty.

Cancel Safety

This method is cancel safe. If join_next is used as the event in a tokio::select! statement and some other branch completes first, it is guaranteed that no tasks were removed from this JoinSet.

source

pub async fn shutdown(&mut self)

Aborts all tasks and waits for them to finish shutting down.

Calling this method is equivalent to calling abort_all and then calling join_next in a loop until it returns None.

This method ignores any panics in the tasks shutting down. When this call returns, the JoinSet will be empty.

source

pub fn abort_all(&mut self)

Aborts all tasks on this JoinSet.

This does not remove the tasks from the JoinSet. To wait for the tasks to complete cancellation, you should call join_next in a loop until the JoinSet is empty.

source