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//! Provides TokioTp executor specific functionality.
//
use
{
crate :: { SpawnHandle, JoinHandle, BlockingHandle } ,
std :: { sync::Arc, future::Future } ,
futures_task :: { FutureObj, Spawn, SpawnError } ,
tokio::runtime :: { Runtime } ,
};
/// An executor that uses [tokio::runtime::Runtime].
///
/// ## Example
///
/// The following example shows how to pass an executor to a library function.
///
/// ```rust
/// use
/// {
/// futures :: { task::{ Spawn, SpawnExt } } ,
/// async_executors :: { TokioTpBuilder } ,
/// tokio::runtime :: { Builder } ,
/// std::convert :: { TryFrom } ,
/// futures::channel :: { oneshot, oneshot::Sender } ,
/// };
///
///
/// fn lib_function( exec: impl Spawn, tx: Sender<&'static str> )
/// {
/// exec.spawn( async
/// {
/// tx.send( "I can spawn from a library" ).expect( "send string" );
///
/// }).expect( "spawn task" );
/// }
///
///
/// fn main()
/// {
/// // You must use the builder. This guarantees that TokioTp is always backed up by a threadpool.
/// // You can set other configurations by calling `tokio_builder()` on TokioTpBuilder, so you get
/// // access to the `tokio::runtime::Builder`.
/// //
/// let exec = TokioTpBuilder::new().build().expect( "create tokio threadpool" );
///
/// let program = async
/// {
/// let (tx, rx) = oneshot::channel();
///
/// lib_function( &exec, tx );
/// assert_eq!( "I can spawn from a library", rx.await.expect( "receive on channel" ) );
/// };
///
/// exec.block_on( program );
/// }
/// ```
///
///
/// ## Unwind Safety.
///
/// You must only spawn futures to this API that are unwind safe. Tokio will wrap it in
/// [std::panic::AssertUnwindSafe] and wrap the poll invocation with [std::panic::catch_unwind].
///
/// They reason that this is fine because they require `Send + 'static` on the future. As far
/// as I can tell this is wrong. Unwind safety can be circumvented in several ways even with
/// `Send + 'static` (eg. `parking_lot::Mutex` is `Send + 'static` but `!UnwindSafe`).
///
/// You should make sure that if your future panics, no code that lives on after the spawned task has
/// unwound, nor any destructors called during the unwind can observe data in an inconsistent state.
///
/// If a future is run with `block_on` as opposed to `spawn`, the panic will not be caught and the
/// thread calling `block_on` will be unwound.
///
/// Note that unwind safety is related to logic errors, not related to the memory safety issues that cannot happen
/// in safe rust (memory safety, undefined behavior, unsoundness, data races, ...). See the relevant
/// [catch_unwind RFC](https://github.com/rust-lang/rfcs/blob/master/text/1236-stabilize-catch-panic.md)
/// and it's discussion threads for more info as well as the documentation of [std::panic::UnwindSafe].
//
#[ derive( Debug, Clone ) ]
//
#[ cfg_attr( nightly, doc(cfg( feature = "tokio_tp" )) ) ]
//
pub struct TokioTp
{
pub(crate) exec: Option< Arc<Runtime> >,
}
impl TokioTp
{
/// Forwards to [Runtime::block_on].
//
pub fn block_on< F: Future >( &self, f: F ) -> F::Output
{
self.exec.as_ref().unwrap().block_on( f )
}
/// See: [tokio::runtime::Runtime::shutdown_timeout]
///
/// This tries to unwrap the Arc<Runtime> we hold, so that works only if no other clones are around. If this is not the
/// only reference, self will be returned to you as an error. It means you cannot shutdown the runtime because there are
/// other clones of the executor still alive.
//
pub fn shutdown_timeout( mut self, duration: std::time::Duration ) -> Result<(), Self>
{
let arc = self.exec.take().unwrap();
let rt = match Arc::try_unwrap( arc )
{
Ok(rt) => rt,
Err(arc) =>
{
self.exec = Some(arc);
return Err(self);
}
};
rt.shutdown_timeout( duration );
Ok(())
}
/// See: [tokio::runtime::Runtime::shutdown_background]
///
/// This tries to unwrap the Arc<Runtime> we hold, so that works only if no other clones are around. If this is not the
/// only reference, self will be returned to you as an error. It means you cannot shutdown the runtime because there are
/// other clones of the executor still alive.
//
pub fn shutdown_background( mut self ) -> Result<(), Self>
{
let arc = self.exec.take().unwrap();
let rt = match Arc::try_unwrap( arc )
{
Ok(rt) => rt,
Err(arc) =>
{
self.exec = Some(arc);
return Err(self);
}
};
rt.shutdown_background();
Ok(())
}
}
#[ cfg( feature = "tokio_io" ) ]
//
#[ cfg_attr( nightly, doc(cfg( feature = "tokio_io" )) ) ]
//
impl crate::TokioIo for TokioTp {}
impl Spawn for TokioTp
{
fn spawn_obj( &self, future: FutureObj<'static, ()> ) -> Result<(), SpawnError>
{
// We drop the JoinHandle, so the task becomes detached.
//
let _ = self.exec.as_ref().unwrap().spawn( future );
Ok(())
}
}
impl<Out: 'static + Send> SpawnHandle<Out> for TokioTp
{
fn spawn_handle_obj( &self, future: FutureObj<'static, Out> ) -> Result<JoinHandle<Out>, SpawnError>
{
let handle = self.exec.as_ref().unwrap().spawn( future );
Ok( JoinHandle::tokio(handle) )
}
}
impl crate::YieldNow for TokioTp {}
impl<R: Send + 'static> crate::SpawnBlocking<R> for TokioTp
{
fn spawn_blocking<F>( &self, f: F ) -> BlockingHandle<R>
where F: FnOnce() -> R + Send + 'static ,
{
let handle = self.exec.as_ref().unwrap().spawn_blocking( f );
BlockingHandle::tokio( handle )
}
fn spawn_blocking_dyn( &self, f: Box< dyn FnOnce()->R + Send > ) -> BlockingHandle<R>
{
self.spawn_blocking( f )
}
}
#[ cfg(all( feature = "timer", not(feature="tokio_timer" )) ) ]
//
#[ cfg_attr( nightly, doc(cfg(all( feature = "timer", feature = "tokio_tp" ))) ) ]
//
impl crate::Timer for TokioTp
{
fn sleep( &self, dur: std::time::Duration ) -> futures_core::future::BoxFuture<'static, ()>
{
Box::pin( futures_timer::Delay::new(dur) )
}
}
#[ cfg( feature = "tokio_timer" ) ]
//
#[ cfg_attr( nightly, doc(cfg(all( feature = "tokio_timer", feature = "tokio_tp" ))) ) ]
//
impl crate::Timer for TokioTp
{
fn sleep( &self, dur: std::time::Duration ) -> futures_core::future::BoxFuture<'static, ()>
{
Box::pin( tokio::time::sleep(dur) )
}
}