Struct CancellationToken 

pub struct CancellationToken { /* private fields */ }

A token for cooperative cancellation.

Clone + Send + Sync. Cloning shares the same cancellation state. Use child() for hierarchical cancellation.

Example

let token = CancellationToken::new();

spawn_boxed(async move {
    token.cancelled().await;
    println!("shutting down");
});

token.cancel();

Implementations

impl CancellationToken

pub fn new() -> Self

Create a new cancellation token.

pub fn child(&self) -> Self

Create a child token. Cancelling this token (or any ancestor) also cancels the child and wakes its waiters. Cancelling the child does NOT cancel the parent.

pub fn cancel(&self)

Cancel this token. All futures awaiting cancelled() will resolve. Child tokens are also cancelled.

pub fn is_cancelled(&self) -> bool

Whether this token has been cancelled. O(1) — single atomic load. Parent cancellation propagates eagerly (sets the child’s flag), so no chain traversal needed.

pub fn drop_guard(self) -> DropGuard

Returns a guard that cancels this token when dropped.

Useful for ensuring cancellation on scope exit or panic.

pub fn cancelled(&self) -> Cancelled

Returns a future that resolves when this token is cancelled.

The returned Cancelled is !Unpin. .await auto-pins; for hot loops re-polling the same future, pin once outside:

let cancelled = token.cancelled();
let mut cancelled = std::pin::pin!(cancelled);
loop { /* poll cancelled.as_mut() */ }

Trait Implementations

impl Clone for CancellationToken

fn clone(&self) -> CancellationToken

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for CancellationToken

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

Formats the value using the given formatter.

impl Default for CancellationToken

fn default() -> Self

Returns the “default value” for a type.