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) -> AbortHandlewhere F: Future<Output = T> + Send + 'static, T: Send,

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

The provided future will start running in the background immediately when this method is called, even if you don’t await anything on this JoinSet.

Panics

This method panics if called outside of a Tokio runtime.

source

pub fn spawn_on<F>(&mut self, task: F, handle: &Handle) -> AbortHandlewhere F: Future<Output = T> + 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.

The provided future will start running in the background immediately when this method is called, even if you don’t await anything on this JoinSet.

source

pub fn spawn_local<F>(&mut self, task: F) -> AbortHandlewhere F: Future<Output = T> + '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.

The provided future will start running in the background immediately when this method is called, even if you don’t await anything on this JoinSet.

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 ) -> AbortHandlewhere F: Future<Output = T> + '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.

Unlike the spawn_local method, this method may be used to spawn local tasks on a LocalSet that is not currently running. The provided future will start running whenever the LocalSet is next started.

source

pub fn spawn_blocking<F>(&mut self, f: F) -> AbortHandlewhere F: FnOnce() -> T + Send + 'static, T: Send,

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

Examples

Spawn multiple blocking 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_blocking(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]);
    }
}
Panics

This method panics if called outside of a Tokio runtime.

source

pub fn spawn_blocking_on<F>(&mut self, f: F, handle: &Handle) -> AbortHandlewhere F: FnOnce() -> T + Send + 'static, T: Send,

Spawn the blocking code on the blocking threadpool of the provided runtime 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

pub fn detach_all(&mut self)

Removes all tasks from this JoinSet without aborting them.

The tasks removed by this call will continue to run in the background even if the JoinSet is dropped.

Trait Implementations§

source§

impl<T> Debug for JoinSet<T>

source§

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

Formats the value using the given formatter. Read more
source§

impl<T> Default for JoinSet<T>

source§

fn default() -> Self

Returns the “default value” for a type. Read more
source§

impl<T> Drop for JoinSet<T>

source§

fn drop(&mut self)

Executes the destructor for this type. Read more

Auto Trait Implementations§

§

impl<T> !RefUnwindSafe for JoinSet<T>

§

impl<T> Send for JoinSet<T>where T: Send,

§

impl<T> Sync for JoinSet<T>where T: Send,

§

impl<T> Unpin for JoinSet<T>

§

impl<T> !UnwindSafe for JoinSet<T>

Blanket Implementations§

source§

impl<T> Any for Twhere T: 'static + ?Sized,

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
source§

impl<T> Borrow<T> for Twhere T: ?Sized,

source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for Twhere T: ?Sized,

source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
source§

impl<T> From<T> for T

source§

fn from(t: T) -> T

Returns the argument unchanged.

source§

impl<T, U> Into<U> for Twhere U: From<T>,

source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

source§

impl<T, U> TryFrom<U> for Twhere U: Into<T>,

§

type Error = Infallible

The type returned in the event of a conversion error.
source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
source§

impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

§

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.