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// This file is part of Substrate.
// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
//! Code to meter unbounded channels.
pub use async_channel::{TryRecvError, TrySendError};
use crate::metrics::{
DROPPED_LABEL, RECEIVED_LABEL, SENT_LABEL, UNBOUNDED_CHANNELS_COUNTER, UNBOUNDED_CHANNELS_SIZE,
};
use async_channel::{Receiver, Sender};
use futures::{
stream::{FusedStream, Stream},
task::{Context, Poll},
use log::error;
use sp_arithmetic::traits::SaturatedConversion;
use std::{
backtrace::Backtrace,
pin::Pin,
sync::{
atomic::{AtomicBool, Ordering},
Arc,
},
/// Wrapper Type around [`async_channel::Sender`] that increases the global
/// measure when a message is added.
#[derive(Debug)]
pub struct TracingUnboundedSender<T> {
inner: Sender<T>,
name: &'static str,
queue_size_warning: usize,
warning_fired: Arc<AtomicBool>,
creation_backtrace: Arc<Backtrace>,
}
// Strangely, deriving `Clone` requires that `T` is also `Clone`.
impl<T> Clone for TracingUnboundedSender<T> {
fn clone(&self) -> Self {
Self {
inner: self.inner.clone(),
name: self.name,
queue_size_warning: self.queue_size_warning,
warning_fired: self.warning_fired.clone(),
creation_backtrace: self.creation_backtrace.clone(),
/// Wrapper Type around [`async_channel::Receiver`] that decreases the global
/// measure when a message is polled.
pub struct TracingUnboundedReceiver<T> {
inner: Receiver<T>,
/// Wrapper around [`async_channel::unbounded`] that tracks the in- and outflow via
/// `UNBOUNDED_CHANNELS_COUNTER` and warns if the message queue grows
/// above the warning threshold.
pub fn tracing_unbounded<T>(
) -> (TracingUnboundedSender<T>, TracingUnboundedReceiver<T>) {
let (s, r) = async_channel::unbounded();
let sender = TracingUnboundedSender {
inner: s,
name,
queue_size_warning,
warning_fired: Arc::new(AtomicBool::new(false)),
creation_backtrace: Arc::new(Backtrace::force_capture()),
let receiver = TracingUnboundedReceiver { inner: r, name: name.into() };
(sender, receiver)
impl<T> TracingUnboundedSender<T> {
/// Proxy function to [`async_channel::Sender`].
pub fn is_closed(&self) -> bool {
self.inner.is_closed()
pub fn close(&self) -> bool {
self.inner.close()
/// Proxy function to `async_channel::Sender::try_send`.
pub fn unbounded_send(&self, msg: T) -> Result<(), TrySendError<T>> {
self.inner.try_send(msg).map(|s| {
UNBOUNDED_CHANNELS_COUNTER.with_label_values(&[self.name, SENT_LABEL]).inc();
UNBOUNDED_CHANNELS_SIZE
.with_label_values(&[self.name])
.set(self.inner.len().saturated_into());
if self.inner.len() >= self.queue_size_warning &&
self.warning_fired
.compare_exchange(false, true, Ordering::Relaxed, Ordering::Relaxed)
.is_ok()
{
error!(
"The number of unprocessed messages in channel `{}` exceeded {}.\n\
The channel was created at:\n{}\n
Last message was sent from:\n{}",
self.name,
self.queue_size_warning,
self.creation_backtrace,
Backtrace::force_capture(),
);
s
})
/// The number of elements in the channel (proxy function to [`async_channel::Sender`]).
pub fn len(&self) -> usize {
self.inner.len()
impl<T> TracingUnboundedReceiver<T> {
/// Proxy function to [`async_channel::Receiver`].
pub fn close(&mut self) -> bool {
/// Proxy function to [`async_channel::Receiver`]
/// that discounts the messages taken out.
pub fn try_recv(&mut self) -> Result<T, TryRecvError> {
self.inner.try_recv().map(|s| {
UNBOUNDED_CHANNELS_COUNTER.with_label_values(&[self.name, RECEIVED_LABEL]).inc();
/// The number of elements in the channel (proxy function to [`async_channel::Receiver`]).
/// The name of this receiver
pub fn name(&self) -> &'static str {
self.name
impl<T> Drop for TracingUnboundedReceiver<T> {
fn drop(&mut self) {
// Close the channel to prevent any further messages to be sent into the channel
self.close();
// The number of messages about to be dropped
let count = self.inner.len();
// Discount the messages
if count > 0 {
UNBOUNDED_CHANNELS_COUNTER
.with_label_values(&[self.name, DROPPED_LABEL])
.inc_by(count.saturated_into());
// Reset the size metric to 0
UNBOUNDED_CHANNELS_SIZE.with_label_values(&[self.name]).set(0);
// Drain all the pending messages in the channel since they can never be accessed,
// this can be removed once https://github.com/smol-rs/async-channel/issues/23 is
// resolved
while let Ok(_) = self.inner.try_recv() {}
impl<T> Unpin for TracingUnboundedReceiver<T> {}
impl<T> Stream for TracingUnboundedReceiver<T> {
type Item = T;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> {
let s = self.get_mut();
match Pin::new(&mut s.inner).poll_next(cx) {
Poll::Ready(msg) => {
if msg.is_some() {
UNBOUNDED_CHANNELS_COUNTER.with_label_values(&[s.name, RECEIVED_LABEL]).inc();
.with_label_values(&[s.name])
.set(s.inner.len().saturated_into());
Poll::Ready(msg)
Poll::Pending => Poll::Pending,
impl<T> FusedStream for TracingUnboundedReceiver<T> {
fn is_terminated(&self) -> bool {
self.inner.is_terminated()
#[cfg(test)]
mod tests {
use super::tracing_unbounded;
use async_channel::{self, RecvError, TryRecvError};
#[test]
fn test_tracing_unbounded_receiver_drop() {
let (tracing_unbounded_sender, tracing_unbounded_receiver) =
tracing_unbounded("test-receiver-drop", 10);
let (tx, rx) = async_channel::unbounded::<usize>();
tracing_unbounded_sender.unbounded_send(tx).unwrap();
drop(tracing_unbounded_receiver);
assert_eq!(rx.try_recv(), Err(TryRecvError::Closed));
assert_eq!(rx.recv_blocking(), Err(RecvError));