mysten_metrics/metered_channel.rs
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// Copyright (c) Mysten Labs, Inc.
// SPDX-License-Identifier: Apache-2.0
#![allow(dead_code)]
use async_trait::async_trait;
use std::future::Future;
// TODO: complete tests - This kinda sorta facades the whole tokio::mpsc::{Sender, Receiver}: without tests, this will be fragile to maintain.
use futures::{FutureExt, Stream, TryFutureExt};
use prometheus::{IntCounter, IntGauge};
use std::task::{Context, Poll};
use tokio::sync::mpsc::{
self,
error::{SendError, TryRecvError, TrySendError},
};
#[cfg(test)]
#[path = "tests/metered_channel_tests.rs"]
mod metered_channel_tests;
/// An [`mpsc::Sender`] with an [`IntGauge`]
/// counting the number of currently queued items.
#[derive(Debug)]
pub struct Sender<T> {
inner: mpsc::Sender<T>,
gauge: IntGauge,
}
impl<T> Clone for Sender<T> {
fn clone(&self) -> Self {
Self {
inner: self.inner.clone(),
gauge: self.gauge.clone(),
}
}
}
impl<T> Sender<T> {
pub fn downgrade(&self) -> WeakSender<T> {
let sender = self.inner.downgrade();
WeakSender {
inner: sender,
gauge: self.gauge.clone(),
}
}
}
/// An [`mpsc::WeakSender`] with an [`IntGauge`]
/// counting the number of currently queued items.
#[derive(Debug)]
pub struct WeakSender<T> {
inner: mpsc::WeakSender<T>,
gauge: IntGauge,
}
impl<T> Clone for WeakSender<T> {
fn clone(&self) -> Self {
Self {
inner: self.inner.clone(),
gauge: self.gauge.clone(),
}
}
}
impl<T> WeakSender<T> {
pub fn upgrade(&self) -> Option<Sender<T>> {
self.inner.upgrade().map(|s| Sender {
inner: s,
gauge: self.gauge.clone(),
})
}
}
/// An [`mpsc::Receiver`] with an [`IntGauge`]
/// counting the number of currently queued items.
#[derive(Debug)]
pub struct Receiver<T> {
inner: mpsc::Receiver<T>,
gauge: IntGauge,
total: Option<IntCounter>,
}
impl<T> Receiver<T> {
/// Receives the next value for this receiver.
/// Decrements the gauge in case of a successful `recv`.
pub async fn recv(&mut self) -> Option<T> {
self.inner
.recv()
.inspect(|opt| {
if opt.is_some() {
self.gauge.dec();
if let Some(total_gauge) = &self.total {
total_gauge.inc();
}
}
})
.await
}
/// Attempts to receive the next value for this receiver.
/// Decrements the gauge in case of a successful `try_recv`.
pub fn try_recv(&mut self) -> Result<T, TryRecvError> {
self.inner.try_recv().inspect(|_| {
self.gauge.dec();
if let Some(total_gauge) = &self.total {
total_gauge.inc();
}
})
}
pub fn blocking_recv(&mut self) -> Option<T> {
self.inner.blocking_recv().inspect(|_| {
self.gauge.dec();
if let Some(total_gauge) = &self.total {
total_gauge.inc();
}
})
}
/// Closes the receiving half of a channel without dropping it.
pub fn close(&mut self) {
self.inner.close()
}
/// Polls to receive the next message on this channel.
/// Decrements the gauge in case of a successful `poll_recv`.
pub fn poll_recv(&mut self, cx: &mut Context<'_>) -> Poll<Option<T>> {
match self.inner.poll_recv(cx) {
res @ Poll::Ready(Some(_)) => {
self.gauge.dec();
if let Some(total_gauge) = &self.total {
total_gauge.inc();
}
res
}
s => s,
}
}
}
impl<T> Unpin for Receiver<T> {}
/// A newtype for an `mpsc::Permit` which allows us to inject gauge accounting
/// in the case the permit is dropped w/o sending
pub struct Permit<'a, T> {
permit: Option<mpsc::Permit<'a, T>>,
gauge_ref: &'a IntGauge,
}
impl<'a, T> Permit<'a, T> {
pub fn new(permit: mpsc::Permit<'a, T>, gauge_ref: &'a IntGauge) -> Permit<'a, T> {
Permit {
permit: Some(permit),
gauge_ref,
}
}
pub fn send(mut self, value: T) {
let sender = self.permit.take().expect("Permit invariant violated!");
sender.send(value);
// skip the drop logic, see https://github.com/tokio-rs/tokio/blob/a66884a2fb80d1180451706f3c3e006a3fdcb036/tokio/src/sync/mpsc/bounded.rs#L1155-L1163
std::mem::forget(self);
}
}
impl<T> Drop for Permit<'_, T> {
fn drop(&mut self) {
// in the case the permit is dropped without sending, we still want to decrease the occupancy of the channel
if self.permit.is_some() {
self.gauge_ref.dec();
}
}
}
impl<T> Sender<T> {
/// Sends a value, waiting until there is capacity.
/// Increments the gauge in case of a successful `send`.
pub async fn send(&self, value: T) -> Result<(), SendError<T>> {
self.inner
.send(value)
.inspect_ok(|_| self.gauge.inc())
.await
}
/// Completes when the receiver has dropped.
pub async fn closed(&self) {
self.inner.closed().await
}
/// Attempts to immediately send a message on this `Sender`
/// Increments the gauge in case of a successful `try_send`.
pub fn try_send(&self, message: T) -> Result<(), TrySendError<T>> {
self.inner
.try_send(message)
// remove this unsightly hack once https://github.com/rust-lang/rust/issues/91345 is resolved
.inspect(|_| {
self.gauge.inc();
})
}
// TODO: facade [`send_timeout`](tokio::mpsc::Sender::send_timeout) under the tokio feature flag "time"
// TODO: facade [`blocking_send`](tokio::mpsc::Sender::blocking_send) under the tokio feature flag "sync"
/// Checks if the channel has been closed. This happens when the
/// [`Receiver`] is dropped, or when the [`Receiver::close`] method is
/// called.
pub fn is_closed(&self) -> bool {
self.inner.is_closed()
}
/// Waits for channel capacity. Once capacity to send one message is
/// available, it is reserved for the caller.
/// Increments the gauge in case of a successful `reserve`.
pub async fn reserve(&self) -> Result<Permit<'_, T>, SendError<()>> {
self.inner
.reserve()
// remove this unsightly hack once https://github.com/rust-lang/rust/issues/91345 is resolved
.map(|val| {
val.map(|permit| {
self.gauge.inc();
Permit::new(permit, &self.gauge)
})
})
.await
}
/// Tries to acquire a slot in the channel without waiting for the slot to become
/// available.
/// Increments the gauge in case of a successful `try_reserve`.
pub fn try_reserve(&self) -> Result<Permit<'_, T>, TrySendError<()>> {
self.inner.try_reserve().map(|val| {
// remove this unsightly hack once https://github.com/rust-lang/rust/issues/91345 is resolved
self.gauge.inc();
Permit::new(val, &self.gauge)
})
}
// TODO: consider exposing the _owned methods
// Note: not exposing `same_channel`, as it is hard to implement with callers able to
// break the coupling between channel and gauge using `gauge`.
/// Returns the current capacity of the channel.
pub fn capacity(&self) -> usize {
self.inner.capacity()
}
// We're voluntarily not putting WeakSender under a facade.
/// Returns a reference to the underlying gauge.
pub fn gauge(&self) -> &IntGauge {
&self.gauge
}
}
////////////////////////////////
// Stream API Wrappers!
////////////////////////////////
/// A wrapper around [`crate::metered_channel::Receiver`] that implements [`Stream`].
#[derive(Debug)]
pub struct ReceiverStream<T> {
inner: Receiver<T>,
}
impl<T> ReceiverStream<T> {
/// Create a new `ReceiverStream`.
pub fn new(recv: Receiver<T>) -> Self {
Self { inner: recv }
}
/// Get back the inner `Receiver`.
pub fn into_inner(self) -> Receiver<T> {
self.inner
}
/// Closes the receiving half of a channel without dropping it.
pub fn close(&mut self) {
self.inner.close()
}
}
impl<T> Stream for ReceiverStream<T> {
type Item = T;
fn poll_next(
mut self: std::pin::Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<Self::Item>> {
self.inner.poll_recv(cx)
}
}
impl<T> AsRef<Receiver<T>> for ReceiverStream<T> {
fn as_ref(&self) -> &Receiver<T> {
&self.inner
}
}
impl<T> AsMut<Receiver<T>> for ReceiverStream<T> {
fn as_mut(&mut self) -> &mut Receiver<T> {
&mut self.inner
}
}
impl<T> From<Receiver<T>> for ReceiverStream<T> {
fn from(recv: Receiver<T>) -> Self {
Self::new(recv)
}
}
// TODO: facade PollSender
// TODO: add prom metrics reporting for gauge and migrate all existing use cases.
////////////////////////////////////////////////////////////////
// Constructor
////////////////////////////////////////////////////////////////
/// Similar to `mpsc::channel`, `channel` creates a pair of `Sender` and `Receiver`
/// Deprecated: use `monitored_mpsc::channel` instead.
#[track_caller]
pub fn channel<T>(size: usize, gauge: &IntGauge) -> (Sender<T>, Receiver<T>) {
gauge.set(0);
let (sender, receiver) = mpsc::channel(size);
(
Sender {
inner: sender,
gauge: gauge.clone(),
},
Receiver {
inner: receiver,
gauge: gauge.clone(),
total: None,
},
)
}
/// Deprecated: use `monitored_mpsc::channel` instead.
#[track_caller]
pub fn channel_with_total<T>(
size: usize,
gauge: &IntGauge,
total_gauge: &IntCounter,
) -> (Sender<T>, Receiver<T>) {
gauge.set(0);
let (sender, receiver) = mpsc::channel(size);
(
Sender {
inner: sender,
gauge: gauge.clone(),
},
Receiver {
inner: receiver,
gauge: gauge.clone(),
total: Some(total_gauge.clone()),
},
)
}
#[async_trait]
pub trait WithPermit<T> {
async fn with_permit<F: Future + Send>(&self, f: F) -> Option<(Permit<T>, F::Output)>;
}
#[async_trait]
impl<T: Send> WithPermit<T> for Sender<T> {
async fn with_permit<F: Future + Send>(&self, f: F) -> Option<(Permit<T>, F::Output)> {
let permit = self.reserve().await.ok()?;
Some((permit, f.await))
}
}