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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/>.
//! Wrapper around a `Future` that reports statistics about when the `Future` is polled.
use futures::prelude::*;
use prometheus_endpoint::{Counter, Histogram, U64};
use std::{
fmt,
pin::Pin,
task::{Context, Poll},
};
/// Wraps around a `Future`. Report the polling duration to the `Histogram` and when the polling
/// starts to the `Counter`.
pub fn with_poll_durations<T>(
poll_duration: Histogram,
poll_start: Counter<U64>,
inner: T,
) -> PrometheusFuture<T> {
PrometheusFuture { inner, poll_duration, poll_start }
}
/// Wraps around `Future` and adds diagnostics to it.
#[pin_project::pin_project]
#[derive(Clone)]
pub struct PrometheusFuture<T> {
/// The inner future doing the actual work.
#[pin]
inner: T,
poll_duration: Histogram,
poll_start: Counter<U64>,
}
impl<T> Future for PrometheusFuture<T>
where
T: Future,
{
type Output = T::Output;
fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
let this = self.project();
this.poll_start.inc();
let _timer = this.poll_duration.start_timer();
Future::poll(this.inner, cx)
// `_timer` is dropped here and will observe the duration
}
}
impl<T> fmt::Debug for PrometheusFuture<T>
where
T: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Debug::fmt(&self.inner, f)
}
}