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|
use {Reactor, Handle, Task};
use atomic_task::AtomicTask;
use futures::{Future, Async, Poll, task};
use std::io;
use std::thread;
use std::sync::Arc;
use std::sync::atomic::AtomicUsize;
use std::sync::atomic::Ordering::SeqCst;
/// Handle to the reactor running on a background thread.
///
/// Instances are created by calling [`Reactor::background`].
///
/// [`Reactor::background`]: struct.Reactor.html#method.background
#[derive(Debug)]
pub struct Background {
/// When `None`, the reactor thread will run until the process terminates.
inner: Option<Inner>,
}
/// Future that resolves when the reactor thread has shutdown.
#[derive(Debug)]
pub struct Shutdown {
inner: Inner,
}
/// Actual Background handle.
#[derive(Debug)]
struct Inner {
/// Handle to the reactor
handle: Handle,
/// Shared state between the background handle and the reactor thread.
shared: Arc<Shared>,
}
#[derive(Debug)]
struct Shared {
/// Signal the reactor thread to shutdown.
shutdown: AtomicUsize,
/// Task to notify when the reactor thread enters a shutdown state.
shutdown_task: AtomicTask,
}
/// Notifies the reactor thread to shutdown once the reactor becomes idle.
const SHUTDOWN_IDLE: usize = 1;
/// Notifies the reactor thread to shutdown immediately.
const SHUTDOWN_NOW: usize = 2;
/// The reactor is currently shutdown.
const SHUTDOWN: usize = 3;
// ===== impl Background =====
impl Background {
/// Launch a reactor in the background and return a handle to the thread.
pub(crate) fn new(reactor: Reactor) -> io::Result<Background> {
// Grab a handle to the reactor
let handle = reactor.handle().clone();
// Create the state shared between the background handle and the reactor
// thread.
let shared = Arc::new(Shared {
shutdown: AtomicUsize::new(0),
shutdown_task: AtomicTask::new(),
});
// For the reactor thread
let shared2 = shared.clone();
// Start the reactor thread
thread::Builder::new()
.spawn(move || run(reactor, shared2))?;
Ok(Background {
inner: Some(Inner {
handle,
shared,
}),
})
}
/// Returns a reference to the reactor handle.
pub fn handle(&self) -> &Handle {
&self.inner.as_ref().unwrap().handle
}
/// Shutdown the reactor on idle.
///
/// Returns a future that completes once the reactor thread has shutdown.
pub fn shutdown_on_idle(mut self) -> Shutdown {
let inner = self.inner.take().unwrap();
inner.shutdown_on_idle();
Shutdown { inner }
}
/// Shutdown the reactor immediately
///
/// Returns a future that completes once the reactor thread has shutdown.
pub fn shutdown_now(mut self) -> Shutdown {
let inner = self.inner.take().unwrap();
inner.shutdown_now();
Shutdown { inner }
}
/// Run the reactor on its thread until the process terminates.
pub fn forget(mut self) {
drop(self.inner.take());
}
}
impl Drop for Background {
fn drop(&mut self) {
let inner = match self.inner.take() {
Some(i) => i,
None => return,
};
inner.shutdown_now();
let shutdown = Shutdown { inner };
let _ = shutdown.wait();
}
}
// ===== impl Shutdown =====
impl Future for Shutdown {
type Item = ();
type Error = ();
fn poll(&mut self) -> Poll<(), ()> {
let task = Task::Futures1(task::current());
self.inner.shared.shutdown_task.register_task(task);
if !self.inner.is_shutdown() {
return Ok(Async::NotReady);
}
Ok(().into())
}
}
// ===== impl Inner =====
impl Inner {
/// Returns true if the reactor thread is shutdown.
fn is_shutdown(&self) -> bool {
self.shared.shutdown.load(SeqCst) == SHUTDOWN
}
/// Notify the reactor thread to shutdown once the reactor transitions to an
/// idle state.
fn shutdown_on_idle(&self) {
self.shared.shutdown
.compare_and_swap(0, SHUTDOWN_IDLE, SeqCst);
self.handle.wakeup();
}
/// Notify the reactor thread to shutdown immediately.
fn shutdown_now(&self) {
let mut curr = self.shared.shutdown.load(SeqCst);
loop {
if curr >= SHUTDOWN_NOW {
return;
}
let act = self.shared.shutdown
.compare_and_swap(curr, SHUTDOWN_NOW, SeqCst);
if act == curr {
self.handle.wakeup();
return;
}
curr = act;
}
}
}
// ===== impl Reactor thread =====
fn run(mut reactor: Reactor, shared: Arc<Shared>) {
debug!("starting background reactor");
loop {
let shutdown = shared.shutdown.load(SeqCst);
if shutdown == SHUTDOWN_NOW {
debug!("shutting background reactor down NOW");
break;
}
if shutdown == SHUTDOWN_IDLE && reactor.is_idle() {
debug!("shutting background reactor on idle");
break;
}
reactor.turn(None).unwrap();
}
drop(reactor);
// Transition the state to shutdown
shared.shutdown.store(SHUTDOWN, SeqCst);
// Notify any waiters
shared.shutdown_task.notify();
debug!("background reactor has shutdown");
}
|
