refactor overseer into proc-macro based pattern (#2962)

polkadot/node/metrics/src/lib.rs

@@ -0,0 +1,121 @@
+// 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 Promethius registry.
+		///
+		/// 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
+	}
+}