Function worker_index 

pub fn worker_index() -> Option<usize>

Returns the index of the current worker thread, if called from a runtime worker thread.

The returned value is a 0-based index matching the worker indices used by RuntimeMetrics methods such as worker_total_busy_duration.

Returns None when called from outside a runtime worker thread (for example, from a blocking thread or a non-Tokio thread). On the multi-thread runtime, the thread that calls Runtime::block_on is not a worker thread, so this also returns None there.

For the current-thread runtime, this returns Some(0) when called from the thread that currently owns the runtime driver. If multiple threads call Runtime::block_on concurrently, calls on threads that do not own the driver return None. A LocalRuntime can only be driven from its owning thread, so calls inside block_on always return Some(0).

Note that the result may change across .await points, as the task may be moved to a different worker thread by the scheduler.

Examples

#[tokio::main(flavor = "multi_thread", worker_threads = 4)]
async fn main() {
    let index = tokio::spawn(async {
        tokio::runtime::worker_index()
    }).await.unwrap();
    println!("Task ran on worker {:?}", index);
}