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// Copyright 2017-2020 Parity Technologies (UK) Ltd.
// This file is part of Polkadot.
// Polkadot 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.
// Polkadot 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 Polkadot. If not, see <http://www.gnu.org/licenses/>.
//! Utility module for subsystems
//!
//! Many subsystems have common interests such as canceling a bunch of spawned jobs,
//! or determining what their validator ID is. These common interests are factored into
//! this module.
//!
//! This crate also reexports Prometheus metric types which are expected to be implemented by subsystems.
#![warn(missing_docs)]
use futures::prelude::*;
use futures_timer::Delay;
use std::{
pin::Pin,
task::{Poll, Context},
time::Duration,
};
pub use metered_channel as metered;
/// This module reexports Prometheus types and defines the [`Metrics`] trait.
pub mod metrics {
/// Reexport Substrate Prometheus types.
pub use substrate_prometheus_endpoint as prometheus;
/// Subsystem- or job-specific Prometheus metrics.
///
/// Usually implemented as a wrapper for `Option<ActualMetrics>`
/// to ensure `Default` bounds or as a dummy type ().
/// Prometheus metrics internally hold an `Arc` reference, so cloning them is fine.
pub trait Metrics: Default + Clone {
/// Try to register metrics in the Prometheus registry.
fn try_register(registry: &prometheus::Registry) -> Result<Self, prometheus::PrometheusError>;
/// Convenience method to register metrics in the optional Prometheus registry.
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///
/// If no registry is provided, returns `Default::default()`. Otherwise, returns the same
/// thing that `try_register` does.
fn register(registry: Option<&prometheus::Registry>) -> Result<Self, prometheus::PrometheusError> {
match registry {
None => Ok(Self::default()),
Some(registry) => Self::try_register(registry),
}
}
}
// dummy impl
impl Metrics for () {
fn try_register(_registry: &prometheus::Registry) -> Result<(), prometheus::PrometheusError> {
Ok(())
}
}
}
#[derive(Copy, Clone)]
enum MetronomeState {
Snooze,
SetAlarm,
}
/// Create a stream of ticks with a defined cycle duration.
pub struct Metronome {
delay: Delay,
period: Duration,
state: MetronomeState,
}
impl Metronome {
/// Create a new metronome source with a defined cycle duration.
pub fn new(cycle: Duration) -> Self {
let period = cycle.into();
Self {
period,
delay: Delay::new(period),
state: MetronomeState::Snooze,
}
}
}
impl futures::Stream for Metronome {
type Item = ();
fn poll_next(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>
) -> Poll<Option<Self::Item>> {
loop {
match self.state {
MetronomeState::SetAlarm => {
let val = self.period.clone();
self.delay.reset(val);
self.state = MetronomeState::Snooze;
}
MetronomeState::Snooze => {
if !Pin::new(&mut self.delay).poll(cx).is_ready() {
break
}
self.state = MetronomeState::SetAlarm;
return Poll::Ready(Some(()));
}
}
}
Poll::Pending
}
}