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use std::{
cell::RefCell,
fmt,
future::Future,
pin::Pin,
sync::atomic::{AtomicUsize, Ordering},
task::{Context, Poll},
thread,
};
use futures_core::ready;
use tokio::sync::mpsc;
use crate::system::{System, SystemCommand};
pub(crate) static COUNT: AtomicUsize = AtomicUsize::new(0);
thread_local!(
static HANDLE: RefCell<Option<ArbiterHandle>> = const { RefCell::new(None) };
);
pub(crate) enum ArbiterCommand {
Stop,
Execute(Pin<Box<dyn Future<Output = ()> + Send>>),
}
impl fmt::Debug for ArbiterCommand {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
ArbiterCommand::Stop => write!(f, "ArbiterCommand::Stop"),
ArbiterCommand::Execute(_) => write!(f, "ArbiterCommand::Execute"),
}
}
}
/// A handle for sending spawn and stop messages to an [Arbiter].
#[derive(Debug, Clone)]
pub struct ArbiterHandle {
tx: mpsc::UnboundedSender<ArbiterCommand>,
}
impl ArbiterHandle {
pub(crate) fn new(tx: mpsc::UnboundedSender<ArbiterCommand>) -> Self {
Self { tx }
}
/// Send a future to the [Arbiter]'s thread and spawn it.
///
/// If you require a result, include a response channel in the future.
///
/// Returns true if future was sent successfully and false if the [Arbiter] has died.
pub fn spawn<Fut>(&self, future: Fut) -> bool
where
Fut: Future<Output = ()> + Send + 'static,
{
self.tx
.send(ArbiterCommand::Execute(Box::pin(future)))
.is_ok()
}
/// Send a function to the [Arbiter]'s thread and execute it.
///
/// Any result from the function is discarded. If you require a result, include a response
/// channel in the function.
///
/// Returns true if function was sent successfully and false if the [Arbiter] has died.
pub fn spawn_fn<F>(&self, f: F) -> bool
where
F: FnOnce() + Send + 'static,
{
self.spawn(async { f() })
}
/// Instruct [Arbiter] to stop processing it's event loop.
///
/// Returns true if stop message was sent successfully and false if the [Arbiter] has
/// been dropped.
pub fn stop(&self) -> bool {
self.tx.send(ArbiterCommand::Stop).is_ok()
}
}
/// An Arbiter represents a thread that provides an asynchronous execution environment for futures
/// and functions.
///
/// When an arbiter is created, it spawns a new [OS thread](thread), and hosts an event loop.
#[derive(Debug)]
pub struct Arbiter {
tx: mpsc::UnboundedSender<ArbiterCommand>,
thread_handle: thread::JoinHandle<()>,
}
impl Arbiter {
/// Spawn a new Arbiter thread and start its event loop.
///
/// # Panics
/// Panics if a [System] is not registered on the current thread.
#[cfg(not(all(target_os = "linux", feature = "io-uring")))]
#[allow(clippy::new_without_default)]
pub fn new() -> Arbiter {
Self::with_tokio_rt(|| {
crate::runtime::default_tokio_runtime().expect("Cannot create new Arbiter's Runtime.")
})
}
/// Spawn a new Arbiter using the [Tokio Runtime](tokio-runtime) returned from a closure.
///
/// [tokio-runtime]: tokio::runtime::Runtime
#[cfg(not(all(target_os = "linux", feature = "io-uring")))]
pub fn with_tokio_rt<F>(runtime_factory: F) -> Arbiter
where
F: FnOnce() -> tokio::runtime::Runtime + Send + 'static,
{
let sys = System::current();
let system_id = sys.id();
let arb_id = COUNT.fetch_add(1, Ordering::Relaxed);
let name = format!("actix-rt|system:{}|arbiter:{}", system_id, arb_id);
let (tx, rx) = mpsc::unbounded_channel();
let (ready_tx, ready_rx) = std::sync::mpsc::channel::<()>();
let thread_handle = thread::Builder::new()
.name(name.clone())
.spawn({
let tx = tx.clone();
move || {
let rt = crate::runtime::Runtime::from(runtime_factory());
let hnd = ArbiterHandle::new(tx);
System::set_current(sys);
HANDLE.with(|cell| *cell.borrow_mut() = Some(hnd.clone()));
// register arbiter
let _ = System::current()
.tx()
.send(SystemCommand::RegisterArbiter(arb_id, hnd));
ready_tx.send(()).unwrap();
// run arbiter event processing loop
rt.block_on(ArbiterRunner { rx });
// deregister arbiter
let _ = System::current()
.tx()
.send(SystemCommand::DeregisterArbiter(arb_id));
}
})
.unwrap_or_else(|err| panic!("Cannot spawn Arbiter's thread: {name:?}: {err:?}"));
ready_rx.recv().unwrap();
Arbiter { tx, thread_handle }
}
/// Spawn a new Arbiter thread and start its event loop with `tokio-uring` runtime.
///
/// # Panics
/// Panics if a [System] is not registered on the current thread.
#[cfg(all(target_os = "linux", feature = "io-uring"))]
#[allow(clippy::new_without_default)]
pub fn new() -> Arbiter {
let sys = System::current();
let system_id = sys.id();
let arb_id = COUNT.fetch_add(1, Ordering::Relaxed);
let name = format!("actix-rt|system:{}|arbiter:{}", system_id, arb_id);
let (tx, rx) = mpsc::unbounded_channel();
let (ready_tx, ready_rx) = std::sync::mpsc::channel::<()>();
let thread_handle = thread::Builder::new()
.name(name.clone())
.spawn({
let tx = tx.clone();
move || {
let hnd = ArbiterHandle::new(tx);
System::set_current(sys);
HANDLE.with(|cell| *cell.borrow_mut() = Some(hnd.clone()));
// register arbiter
let _ = System::current()
.tx()
.send(SystemCommand::RegisterArbiter(arb_id, hnd));
ready_tx.send(()).unwrap();
// run arbiter event processing loop
tokio_uring::start(ArbiterRunner { rx });
// deregister arbiter
let _ = System::current()
.tx()
.send(SystemCommand::DeregisterArbiter(arb_id));
}
})
.unwrap_or_else(|err| panic!("Cannot spawn Arbiter's thread: {name:?}: {err:?}"));
ready_rx.recv().unwrap();
Arbiter { tx, thread_handle }
}
/// Sets up an Arbiter runner in a new System using the environment's local set.
pub(crate) fn in_new_system() -> ArbiterHandle {
let (tx, rx) = mpsc::unbounded_channel();
let hnd = ArbiterHandle::new(tx);
HANDLE.with(|cell| *cell.borrow_mut() = Some(hnd.clone()));
crate::spawn(ArbiterRunner { rx });
hnd
}
/// Return a handle to the this Arbiter's message sender.
pub fn handle(&self) -> ArbiterHandle {
ArbiterHandle::new(self.tx.clone())
}
/// Return a handle to the current thread's Arbiter's message sender.
///
/// # Panics
/// Panics if no Arbiter is running on the current thread.
pub fn current() -> ArbiterHandle {
HANDLE.with(|cell| match *cell.borrow() {
Some(ref hnd) => hnd.clone(),
None => panic!("Arbiter is not running."),
})
}
/// Try to get current running arbiter handle.
///
/// Returns `None` if no Arbiter has been started.
///
/// Unlike [`current`](Self::current), this never panics.
pub fn try_current() -> Option<ArbiterHandle> {
HANDLE.with(|cell| cell.borrow().clone())
}
/// Stop Arbiter from continuing it's event loop.
///
/// Returns true if stop message was sent successfully and false if the Arbiter has been dropped.
pub fn stop(&self) -> bool {
self.tx.send(ArbiterCommand::Stop).is_ok()
}
/// Send a future to the Arbiter's thread and spawn it.
///
/// If you require a result, include a response channel in the future.
///
/// Returns true if future was sent successfully and false if the Arbiter has died.
#[track_caller]
pub fn spawn<Fut>(&self, future: Fut) -> bool
where
Fut: Future<Output = ()> + Send + 'static,
{
self.tx
.send(ArbiterCommand::Execute(Box::pin(future)))
.is_ok()
}
/// Send a function to the Arbiter's thread and execute it.
///
/// Any result from the function is discarded. If you require a result, include a response
/// channel in the function.
///
/// Returns true if function was sent successfully and false if the Arbiter has died.
#[track_caller]
pub fn spawn_fn<F>(&self, f: F) -> bool
where
F: FnOnce() + Send + 'static,
{
self.spawn(async { f() })
}
/// Wait for Arbiter's event loop to complete.
///
/// Joins the underlying OS thread handle. See [`JoinHandle::join`](thread::JoinHandle::join).
pub fn join(self) -> thread::Result<()> {
self.thread_handle.join()
}
}
/// A persistent future that processes [Arbiter] commands.
struct ArbiterRunner {
rx: mpsc::UnboundedReceiver<ArbiterCommand>,
}
impl Future for ArbiterRunner {
type Output = ();
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
// process all items currently buffered in channel
loop {
match ready!(self.rx.poll_recv(cx)) {
// channel closed; no more messages can be received
None => return Poll::Ready(()),
// process arbiter command
Some(item) => match item {
ArbiterCommand::Stop => {
return Poll::Ready(());
}
ArbiterCommand::Execute(task_fut) => {
tokio::task::spawn_local(task_fut);
}
},
}
}
}
}