Further improved availability recovery (#3711)

* WiP.

* Things compile.

* cargo fmt

* Passing tests + fix warnings.

* Metrics for availability recovery.

* Basic test.

* Fix typos and actually check for overflow.

* cargo fmt

* Register metrics.

* More tests.

* Fix warning.

* cargo +nightly fmt

* Fix metrics

* Get rid of unsafe.

* tabify

* spellcheck

Co-authored-by: Andronik Ordian <write@reusable.software>
Co-authored-by: Bastian Köcher <info@kchr.de>

polkadot/node/network/availability-recovery/src/metrics.rs

@@ -0,0 +1,132 @@
+// Copyright 2021 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/>.
+
+use polkadot_node_subsystem_util::{
+	metrics,
+	metrics::{
+		prometheus,
+		prometheus::{Counter, CounterVec, Opts, PrometheusError, Registry, U64},
+	},
+};
+
+/// Availability Distribution metrics.
+#[derive(Clone, Default)]
+pub struct Metrics(Option<MetricsInner>);
+
+#[derive(Clone)]
+struct MetricsInner {
+	/// Number of sent chunk requests.
+	///
+	/// Gets incremented on each sent chunk requests.
+	chunk_requests_issued: Counter<U64>,
+
+	/// A counter for finished chunk requests.
+	///
+	/// Split by result:
+	/// - `no_such_chunk` ... peer did not have the requested chunk
+	/// - `timeout` ... request timed out.
+	/// - `network_error` ... Some networking issue except timeout
+	/// - `invalid` ... Chunk was received, but not valid.
+	/// - `success`
+	chunk_requests_finished: CounterVec<U64>,
+	/// The duration of request to response.
+	time_chunk_request: prometheus::Histogram,
+}
+
+impl Metrics {
+	/// Create new dummy metrics, not reporting anything.
+	pub fn new_dummy() -> Self {
+		Metrics(None)
+	}
+
+	/// Increment counter on fetched labels.
+	pub fn on_chunk_request_issued(&self) {
+		if let Some(metrics) = &self.0 {
+			metrics.chunk_requests_issued.inc()
+		}
+	}
+
+	/// A chunk request timed out.
+	pub fn on_chunk_request_timeout(&self) {
+		if let Some(metrics) = &self.0 {
+			metrics.chunk_requests_finished.with_label_values(&["timeout"]).inc()
+		}
+	}
+
+	/// A chunk request failed because validator did not have its chunk.
+	pub fn on_chunk_request_no_such_chunk(&self) {
+		if let Some(metrics) = &self.0 {
+			metrics.chunk_requests_finished.with_label_values(&["no_such_chunk"]).inc()
+		}
+	}
+
+	/// A chunk request failed for some non timeout related network error.
+	pub fn on_chunk_request_error(&self) {
+		if let Some(metrics) = &self.0 {
+			metrics.chunk_requests_finished.with_label_values(&["error"]).inc()
+		}
+	}
+
+	/// A chunk request succeeded, but was not valid.
+	pub fn on_chunk_request_invalid(&self) {
+		if let Some(metrics) = &self.0 {
+			metrics.chunk_requests_finished.with_label_values(&["invalid"]).inc()
+		}
+	}
+
+	/// A chunk request succeeded.
+	pub fn on_chunk_request_succeeded(&self) {
+		if let Some(metrics) = &self.0 {
+			metrics.chunk_requests_finished.with_label_values(&["success"]).inc()
+		}
+	}
+	/// Get a timer to time request/response duration.
+	pub fn time_chunk_request(&self) -> Option<metrics::prometheus::prometheus::HistogramTimer> {
+		self.0.as_ref().map(|metrics| metrics.time_chunk_request.start_timer())
+	}
+}
+
+impl metrics::Metrics for Metrics {
+	fn try_register(registry: &Registry) -> Result<Self, PrometheusError> {
+		let metrics = MetricsInner {
+			chunk_requests_issued: prometheus::register(
+				Counter::new(
+					"parachain_availability_recovery_chunk_requests_issued",
+					"Total number of issued chunk requests.",
+				)?,
+				registry,
+			)?,
+			chunk_requests_finished: prometheus::register(
+				CounterVec::new(
+					Opts::new(
+						"parachain_availability_recovery_chunk_requests_finished",
+						"Total number of chunk requests finished.",
+					),
+					&["result"],
+				)?,
+				registry,
+			)?,
+			time_chunk_request: prometheus::register(
+				prometheus::Histogram::with_opts(prometheus::HistogramOpts::new(
+					"parachain_availability_recovery_time_chunk_request",
+					"Time spent waiting for a response to a chunk request",
+				))?,
+				registry,
+			)?,
+		};
+		Ok(Metrics(Some(metrics)))
+	}
+}