Struct BackgroundShutdownRuntime

pub struct BackgroundShutdownRuntime(ManuallyDrop<Runtime>);

A wrapper around [Runtime] that shuts down the runtime in the background when dropped.

This is necessary because directly dropping a nested runtime is not allowed in a parent runtime.

Tuple Fields

0: ManuallyDrop<Runtime>

Methods from Deref<Target = Runtime>

pub fn handle(&self) -> &Handle

Returns a handle to the runtime’s spawner.

The returned handle can be used to spawn tasks that run on this runtime, and can be cloned to allow moving the Handle to other threads.

Calling [Handle::block_on] on a handle to a current_thread runtime is error-prone. Refer to the documentation of [Handle::block_on] for more.

Examples

use tokio::runtime::Runtime;

let rt = Runtime::new()
    .unwrap();

let handle = rt.handle();

// Use the handle...

pub fn spawn<F>(&self, future: F) -> JoinHandle<<F as Future>::Output>

where F: Future + Send + 'static, <F as Future>::Output: Send + 'static,

Spawns a future onto the Tokio runtime.

This spawns the given future onto the runtime’s executor, usually a thread pool. The thread pool is then responsible for polling the future until it completes.

The provided future will start running in the background immediately when spawn is called, even if you don’t await the returned JoinHandle.

See module level documentation for more details.

Examples

use tokio::runtime::Runtime;

// Create the runtime
let rt = Runtime::new().unwrap();

// Spawn a future onto the runtime
rt.spawn(async {
    println!("now running on a worker thread");
});

pub fn spawn_blocking<F, R>(&self, func: F) -> JoinHandle<R>

where F: FnOnce() -> R + Send + 'static, R: Send + 'static,

Runs the provided function on an executor dedicated to blocking operations.

Examples

use tokio::runtime::Runtime;

// Create the runtime
let rt = Runtime::new().unwrap();

// Spawn a blocking function onto the runtime
rt.spawn_blocking(|| {
    println!("now running on a worker thread");
});

pub fn block_on<F>(&self, future: F) -> <F as Future>::Output

where F: Future,

Runs a future to completion on the Tokio runtime. This is the runtime’s entry point.

This runs the given future on the current thread, blocking until it is complete, and yielding its resolved result. Any tasks or timers which the future spawns internally will be executed on the runtime.

Non-worker future

Note that the future required by this function does not run as a worker. The expectation is that other tasks are spawned by the future here. Awaiting on other futures from the future provided here will not perform as fast as those spawned as workers.

Multi thread scheduler

When the multi thread scheduler is used this will allow futures to run within the io driver and timer context of the overall runtime.

Any spawned tasks will continue running after block_on returns.

Current thread scheduler

When the current thread scheduler is enabled block_on can be called concurrently from multiple threads. The first call will take ownership of the io and timer drivers. This means other threads which do not own the drivers will hook into that one. When the first block_on completes, other threads will be able to “steal” the driver to allow continued execution of their futures.

Any spawned tasks will be suspended after block_on returns. Calling block_on again will resume previously spawned tasks.

Panics

This function panics if the provided future panics, or if called within an asynchronous execution context.

Examples

use tokio::runtime::Runtime;

// Create the runtime
let rt  = Runtime::new().unwrap();

// Execute the future, blocking the current thread until completion
rt.block_on(async {
    println!("hello");
});

pub fn enter(&self) -> EnterGuard<'_>

Enters the runtime context.

This allows you to construct types that must have an executor available on creation such as Sleep or TcpStream. It will also allow you to call methods such as tokio::spawn.

Example

use tokio::runtime::Runtime;
use tokio::task::JoinHandle;

fn function_that_spawns(msg: String) -> JoinHandle<()> {
    // Had we not used `rt.enter` below, this would panic.
    tokio::spawn(async move {
        println!("{}", msg);
    })
}

fn main() {
    let rt = Runtime::new().unwrap();

    let s = "Hello World!".to_string();

    // By entering the context, we tie `tokio::spawn` to this executor.
    let _guard = rt.enter();
    let handle = function_that_spawns(s);

    // Wait for the task before we end the test.
    rt.block_on(handle).unwrap();
}

pub fn metrics(&self) -> RuntimeMetrics

Returns a view that lets you get information about how the runtime is performing.

Trait Implementations

impl Deref for BackgroundShutdownRuntime

type Target = Runtime

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl DerefMut for BackgroundShutdownRuntime

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl Drop for BackgroundShutdownRuntime

fn drop(&mut self)

Executes the destructor for this type.

impl From<Runtime> for BackgroundShutdownRuntime

fn from(runtime: Runtime) -> Self

Converts to this type from the input type.