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update buffers to use Tokio 0.3 MPSC channels #759
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598c9be
switch buffers to use Tokio 0.3 channels
hawkw eb24cd8
add tests based on Tokio's
hawkw 14cc5a7
let's just use tokio's error types
hawkw 6904956
Update linkerd/buffer/src/dispatch.rs
hawkw e2046e3
Update linkerd/buffer/src/dispatch.rs
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,17 @@ | ||
[package] | ||
name = "linkerd2-channel" | ||
version = "0.1.0" | ||
authors = ["Linkerd Developers <cncf-linkerd-dev@lists.cncf.io>"] | ||
edition = "2018" | ||
publish = false | ||
description = """ | ||
A bounded MPSC channel where senders expose a `poll_ready` method. | ||
""" | ||
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[dependencies] | ||
tokio = { version = "0.3", features = ["sync", "stream"] } | ||
futures = "0.3" | ||
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[dev-dependencies] | ||
tokio = { version = "0.3", features = ["sync", "stream", "macros"] } | ||
tokio-test = "0.3" |
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,191 @@ | ||
use futures::{future, ready, Stream}; | ||
use std::sync::{Arc, Weak}; | ||
use std::task::{Context, Poll}; | ||
use std::{fmt, future::Future, mem, pin::Pin}; | ||
use tokio::sync::{mpsc, OwnedSemaphorePermit as Permit, Semaphore}; | ||
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use self::error::{SendError, TrySendError}; | ||
pub use tokio::sync::mpsc::error; | ||
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/// Returns a new pollable, bounded MPSC channel. | ||
/// | ||
/// Unlike `tokio::sync`'s `MPSC` channel, this channel exposes a `poll_ready` | ||
/// function, at the cost of an allocation when driving it to readiness. | ||
pub fn channel<T>(buffer: usize) -> (Sender<T>, Receiver<T>) { | ||
assert!(buffer > 0, "mpsc bounded channel requires buffer > 0"); | ||
let semaphore = Arc::new(Semaphore::new(buffer)); | ||
let (tx, rx) = mpsc::unbounded_channel(); | ||
let rx = Receiver { | ||
rx, | ||
semaphore: Arc::downgrade(&semaphore), | ||
buffer, | ||
}; | ||
let tx = Sender { | ||
tx, | ||
semaphore, | ||
state: State::Empty, | ||
}; | ||
(tx, rx) | ||
} | ||
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/// A bounded, pollable MPSC sender. | ||
/// | ||
/// This is similar to Tokio's bounded MPSC channel's `Sender` type, except that | ||
/// it exposes a `poll_ready` function, at the cost of an allocation when | ||
/// driving it to readiness. | ||
pub struct Sender<T> { | ||
tx: mpsc::UnboundedSender<(T, Permit)>, | ||
semaphore: Arc<Semaphore>, | ||
state: State, | ||
} | ||
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/// A bounded MPSC receiver. | ||
/// | ||
/// This is similar to Tokio's bounded MPSC channel's `Receiver` type. | ||
pub struct Receiver<T> { | ||
rx: mpsc::UnboundedReceiver<(T, Permit)>, | ||
semaphore: Weak<Semaphore>, | ||
buffer: usize, | ||
} | ||
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enum State { | ||
Waiting(Pin<Box<dyn Future<Output = Permit> + Send + Sync>>), | ||
Acquired(Permit), | ||
Empty, | ||
} | ||
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impl<T> Sender<T> { | ||
pub fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), SendError<()>>> { | ||
loop { | ||
self.state = match self.state { | ||
State::Empty => State::Waiting(Box::pin(self.semaphore.clone().acquire_owned())), | ||
State::Waiting(ref mut f) => State::Acquired(ready!(Pin::new(f).poll(cx))), | ||
State::Acquired(_) if self.tx.is_closed() => { | ||
return Poll::Ready(Err(SendError(()))) | ||
} | ||
State::Acquired(_) => return Poll::Ready(Ok(())), | ||
} | ||
} | ||
} | ||
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pub async fn ready(&mut self) -> Result<(), SendError<()>> { | ||
future::poll_fn(|cx| self.poll_ready(cx)).await | ||
} | ||
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pub fn try_send(&mut self, value: T) -> Result<(), TrySendError<T>> { | ||
if self.tx.is_closed() { | ||
return Err(TrySendError::Closed(value)); | ||
} | ||
self.state = match mem::replace(&mut self.state, State::Empty) { | ||
// Have we previously acquired a permit? | ||
State::Acquired(permit) => { | ||
self.send2(value, permit); | ||
return Ok(()); | ||
} | ||
// Okay, can we acquire a permit now? | ||
State::Empty => { | ||
if let Ok(permit) = self.semaphore.clone().try_acquire_owned() { | ||
self.send2(value, permit); | ||
return Ok(()); | ||
} | ||
State::Empty | ||
} | ||
state => state, | ||
}; | ||
Err(TrySendError::Full(value)) | ||
} | ||
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pub async fn send(&mut self, value: T) -> Result<(), SendError<T>> { | ||
if let Err(_) = self.ready().await { | ||
return Err(SendError(value)); | ||
} | ||
match mem::replace(&mut self.state, State::Empty) { | ||
State::Acquired(permit) => { | ||
self.send2(value, permit); | ||
Ok(()) | ||
} | ||
state => panic!("unexpected state after poll_ready: {:?}", state), | ||
} | ||
} | ||
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fn send2(&mut self, value: T, permit: Permit) { | ||
self.tx.send((value, permit)).ok().expect("was not closed"); | ||
} | ||
} | ||
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impl<T> Clone for Sender<T> { | ||
fn clone(&self) -> Self { | ||
Self { | ||
tx: self.tx.clone(), | ||
semaphore: self.semaphore.clone(), | ||
state: State::Empty, | ||
} | ||
} | ||
} | ||
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impl<T> fmt::Debug for Sender<T> { | ||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
f.debug_struct("Sender") | ||
.field("message_type", &std::any::type_name::<T>()) | ||
.field("state", &self.state) | ||
.field("semaphore", &self.semaphore) | ||
.finish() | ||
} | ||
} | ||
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// === impl Receiver === | ||
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impl<T> Receiver<T> { | ||
pub async fn recv(&mut self) -> Option<T> { | ||
self.rx.recv().await.map(|(t, _)| t) | ||
} | ||
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pub fn poll_recv(&mut self, cx: &mut Context<'_>) -> Poll<Option<T>> { | ||
let res = ready!(Pin::new(&mut self.rx).poll_next(cx)); | ||
Poll::Ready(res.map(|(t, _)| t)) | ||
} | ||
} | ||
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impl<T> Stream for Receiver<T> { | ||
type Item = T; | ||
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> { | ||
let res = ready!(Pin::new(&mut self.as_mut().rx).poll_next(cx)); | ||
Poll::Ready(res.map(|(t, _)| t)) | ||
} | ||
} | ||
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impl<T> Drop for Receiver<T> { | ||
fn drop(&mut self) { | ||
if let Some(semaphore) = self.semaphore.upgrade() { | ||
// Close the buffer by releasing any senders waiting on channel capacity. | ||
// If more than `usize::MAX >> 3` permits are added to the semaphore, it | ||
// will panic. | ||
const MAX: usize = std::usize::MAX >> 4; | ||
semaphore.add_permits(MAX - self.buffer - semaphore.available_permits()); | ||
} | ||
} | ||
} | ||
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impl<T> fmt::Debug for Receiver<T> { | ||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
f.debug_struct("Receiver") | ||
.field("message_type", &std::any::type_name::<T>()) | ||
.field("semaphore", &self.semaphore) | ||
.finish() | ||
} | ||
} | ||
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// === impl State === | ||
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impl fmt::Debug for State { | ||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
fmt::Display::fmt( | ||
match self { | ||
State::Acquired(_) => "State::Acquired(..)", | ||
State::Waiting(_) => "State::Waiting(..)", | ||
State::Empty => "State::Empty", | ||
}, | ||
f, | ||
) | ||
} | ||
} |
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way ahead of you, buddy e2046e3 :D
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@hawkw i think that got the other break, but there were two.. so i think this is still relevant?