use futures::channel::mpsc;
use futures::executor::block_on;
use futures::future::Future;
use futures::sink::SinkExt;
use futures::stream::StreamExt;
use futures::task::{Context, Poll};
use std::pin::Pin;
use std::sync::{Arc, Weak};
use std::thread;
use std::time::{Duration, Instant};
#[test]
fn smoke() {
let (mut sender, receiver) = mpsc::channel(1);
let t = thread::spawn(move || while let Ok(()) = block_on(sender.send(42)) {});
// `receiver` needs to be dropped for `sender` to stop sending and therefore before the join.
block_on(receiver.take(3).for_each(|_| futures::future::ready(())));
t.join().unwrap()
}
#[test]
fn multiple_senders_disconnect() {
{
let (mut tx1, mut rx) = mpsc::channel(1);
let (tx2, mut tx3, mut tx4) = (tx1.clone(), tx1.clone(), tx1.clone());
// disconnect, dropping and Sink::poll_close should all close this sender but leave the
// channel open for other senders
tx1.disconnect();
drop(tx2);
block_on(tx3.close()).unwrap();
assert!(tx1.is_closed());
assert!(tx3.is_closed());
assert!(!tx4.is_closed());
block_on(tx4.send(5)).unwrap();
assert_eq!(block_on(rx.next()), Some(5));
// dropping the final sender will close the channel
drop(tx4);
assert_eq!(block_on(rx.next()), None);
}
{
let (mut tx1, mut rx) = mpsc::unbounded();
let (tx2, mut tx3, mut tx4) = (tx1.clone(), tx1.clone(), tx1.clone());
// disconnect, dropping and Sink::poll_close should all close this sender but leave the
// channel open for other senders
tx1.disconnect();
drop(tx2);
block_on(tx3.close()).unwrap();
assert!(tx1.is_closed());
assert!(tx3.is_closed());
assert!(!tx4.is_closed());
block_on(tx4.send(5)).unwrap();
assert_eq!(block_on(rx.next()), Some(5));
// dropping the final sender will close the channel
drop(tx4);
assert_eq!(block_on(rx.next()), None);
}
}
#[test]
fn multiple_senders_close_channel() {
{
let (mut tx1, mut rx) = mpsc::channel(1);
let mut tx2 = tx1.clone();
// close_channel should shut down the whole channel
tx1.close_channel();
assert!(tx1.is_closed());
assert!(tx2.is_closed());
let err = block_on(tx2.send(5)).unwrap_err();
assert!(err.is_disconnected());
assert_eq!(block_on(rx.next()), None);
}
{
let (tx1, mut rx) = mpsc::unbounded();
let mut tx2 = tx1.clone();
// close_channel should shut down the whole channel
tx1.close_channel();
assert!(tx1.is_closed());
assert!(tx2.is_closed());
let err = block_on(tx2.send(5)).unwrap_err();
assert!(err.is_disconnected());
assert_eq!(block_on(rx.next()), None);
}
}
#[test]
fn single_receiver_drop_closes_channel_and_drains() {
{
let ref_count = Arc::new(0);
let weak_ref = Arc::downgrade(&ref_count);
let (sender, receiver) = mpsc::unbounded();
sender.unbounded_send(ref_count).expect("failed to send");
// Verify that the sent message is still live.
assert!(weak_ref.upgrade().is_some());
drop(receiver);
// The sender should know the channel is closed.
assert!(sender.is_closed());
// Verify that the sent message has been dropped.
assert!(weak_ref.upgrade().is_none());
}
{
let ref_count = Arc::new(0);
let weak_ref = Arc::downgrade(&ref_count);
let (mut sender, receiver) = mpsc::channel(1);
sender.try_send(ref_count).expect("failed to send");
// Verify that the sent message is still live.
assert!(weak_ref.upgrade().is_some());
drop(receiver);
// The sender should know the channel is closed.
assert!(sender.is_closed());
// Verify that the sent message has been dropped.
assert!(weak_ref.upgrade().is_none());
assert!(sender.is_closed());
}
}
// Stress test that `try_send()`s occurring concurrently with receiver
// close/drops don't appear as successful sends.
#[cfg_attr(miri, ignore)] // Miri is too slow
#[test]
fn stress_try_send_as_receiver_closes() {
const AMT: usize = 10000;
// To provide variable timing characteristics (in the hopes of
// reproducing the collision that leads to a race), we busy-re-poll
// the test MPSC receiver a variable number of times before actually
// stopping. We vary this countdown between 1 and the following
// value.
const MAX_COUNTDOWN: usize = 20;
// When we detect that a successfully sent item is still in the
// queue after a disconnect, we spin for up to 100ms to confirm that
// it is a persistent condition and not a concurrency illusion.
const SPIN_TIMEOUT_S: u64 = 10;
const SPIN_SLEEP_MS: u64 = 10;
struct TestRx {
rx: mpsc::Receiver<Arc<()>>,
// The number of times to query `rx` before dropping it.
poll_count: usize,
}
struct TestTask {
command_rx: mpsc::Receiver<TestRx>,
test_rx: Option<mpsc::Receiver<Arc<()>>>,
countdown: usize,
}
impl TestTask {
/// Create a new TestTask
fn new() -> (TestTask, mpsc::Sender<TestRx>) {
let (command_tx, command_rx) = mpsc::channel::<TestRx>(0);
(
TestTask {
command_rx,
test_rx: None,
countdown: 0, // 0 means no countdown is in progress.
},
command_tx,
)
}
}
impl Future for TestTask {
type Output = ();
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
// Poll the test channel, if one is present.
if let Some(rx) = &mut self.test_rx {
if let Poll::Ready(v) = rx.poll_next_unpin(cx) {
let _ = v.expect("test finished unexpectedly!");
}
self.countdown -= 1;
// Busy-poll until the countdown is finished.
cx.waker().wake_by_ref();
}
// Accept any newly submitted MPSC channels for testing.
match self.command_rx.poll_next_unpin(cx) {
Poll::Ready(Some(TestRx { rx, poll_count })) => {
self.test_rx = Some(rx);
self.countdown = poll_count;
cx.waker().wake_by_ref();
}
Poll::Ready(None) => return Poll::Ready(()),
Poll::Pending => {}
}
if self.countdown == 0 {
// Countdown complete -- drop the Receiver.
self.test_rx = None;
}
Poll::Pending
}
}
let (f, mut cmd_tx) = TestTask::new();
let bg = thread::spawn(move || block_on(f));
for i in 0..AMT {
let (mut test_tx, rx) = mpsc::channel(0);
let poll_count = i % MAX_COUNTDOWN;
cmd_tx.try_send(TestRx { rx, poll_count }).unwrap();
let mut prev_weak: Option<Weak<()>> = None;
let mut attempted_sends = 0;
let mut successful_sends = 0;
loop {
// Create a test item.
let item = Arc::new(());
let weak = Arc::downgrade(&item);
match test_tx.try_send(item) {
Ok(_) => {
prev_weak = Some(weak);
successful_sends += 1;
}
Err(ref e) if e.is_full() => {}
Err(ref e) if e.is_disconnected() => {
// Test for evidence of the race condition.
if let Some(prev_weak) = prev_weak {
if prev_weak.upgrade().is_some() {
// The previously sent item is still allocated.
// However, there appears to be some aspect of the
// concurrency that can legitimately cause the Arc
// to be momentarily valid. Spin for up to 100ms
// waiting for the previously sent item to be
// dropped.
let t0 = Instant::now();
let mut spins = 0;
loop {
if prev_weak.upgrade().is_none() {
break;
}
assert!(
t0.elapsed() < Duration::from_secs(SPIN_TIMEOUT_S),
"item not dropped on iteration {} after \
{} sends ({} successful). spin=({})",
i,
attempted_sends,
successful_sends,
spins
);
spins += 1;
thread::sleep(Duration::from_millis(SPIN_SLEEP_MS));
}
}
}
break;
}
Err(ref e) => panic!("unexpected error: {}", e),
}
attempted_sends += 1;
}
}
drop(cmd_tx);
bg.join().expect("background thread join");
}
#[test]
fn unbounded_try_next_after_none() {
let (tx, mut rx) = mpsc::unbounded::<String>();
// Drop the sender, close the channel.
drop(tx);
// Receive the end of channel.
assert_eq!(Ok(None), rx.try_next().map_err(|_| ()));
// None received, check we can call `try_next` again.
assert_eq!(Ok(None), rx.try_next().map_err(|_| ()));
}
#[test]
fn bounded_try_next_after_none() {
let (tx, mut rx) = mpsc::channel::<String>(17);
// Drop the sender, close the channel.
drop(tx);
// Receive the end of channel.
assert_eq!(Ok(None), rx.try_next().map_err(|_| ()));
// None received, check we can call `try_next` again.
assert_eq!(Ok(None), rx.try_next().map_err(|_| ()));
}
