1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143

// Copyright 2020 Parity Technologies (UK) Ltd.
// This file is part of Substrate.

// Substrate 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.

// Substrate 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 Substrate.  If not, see <http://www.gnu.org/licenses/>.

//! Metrics that are collected from existing sources.

use prometheus::core::{Collector, Desc, Describer, Number, Opts};
use prometheus::proto;
use std::{cmp::Ordering, marker::PhantomData};

/// A counter whose values are obtained from an existing source.
///
/// > **Note*: The counter values provided by the source `S`
/// > must be monotonically increasing. Otherwise use a
/// > [`SourcedGauge`] instead.
pub type SourcedCounter<S> = SourcedMetric<Counter, S>;

/// A gauge whose values are obtained from an existing source.
pub type SourcedGauge<S> = SourcedMetric<Gauge, S>;

/// The type of a sourced counter.
#[derive(Copy, Clone)]
pub enum Counter {}

/// The type of a sourced gauge.
#[derive(Copy, Clone)]
pub enum Gauge {}

/// A metric whose values are obtained from an existing source,
/// instead of being independently recorded.
#[derive(Debug, Clone)]
pub struct SourcedMetric<T, S> {
	source: S,
	desc: Desc,
	_type: PhantomData<T>,
}

/// A source of values for a [`SourcedMetric`].
pub trait MetricSource: Sync + Send + Clone {
	/// The type of the collected values.
	type N: Number;
	/// Collects the current values of the metrics from the source.
	fn collect(&self, set: impl FnMut(&[&str], Self::N));
}

impl<T: SourcedType, S: MetricSource> SourcedMetric<T, S> {
	/// Creates a new metric that obtains its values from the given source.
	pub fn new(opts: &Opts, source: S) -> prometheus::Result<Self> {
		let desc = opts.describe()?;
		Ok(Self { source, desc, _type: PhantomData })
	}
}

impl<T: SourcedType, S: MetricSource> Collector for SourcedMetric<T, S> {
	fn desc(&self) -> Vec<&Desc> {
		vec![&self.desc]
	}

	fn collect(&self) -> Vec<proto::MetricFamily> {
		let mut counters = Vec::new();

		self.source.collect(|label_values, value| {
			let mut m = proto::Metric::default();

			match T::proto() {
				proto::MetricType::COUNTER => {
					let mut c = proto::Counter::default();
					c.set_value(value.into_f64());
					m.set_counter(c);
				}
				proto::MetricType::GAUGE => {
					let mut g = proto::Gauge::default();
					g.set_value(value.into_f64());
					m.set_gauge(g);
				}
				t => {
					log::error!("Unsupported sourced metric type: {:?}", t);
				}
			}

			debug_assert_eq!(self.desc.variable_labels.len(), label_values.len());
			match self.desc.variable_labels.len().cmp(&label_values.len()) {
				Ordering::Greater =>
					log::warn!("Missing label values for sourced metric {}", self.desc.fq_name),
				Ordering::Less =>
					log::warn!("Too many label values for sourced metric {}", self.desc.fq_name),
				Ordering::Equal => {}
			}

			m.set_label(self.desc.variable_labels.iter().zip(label_values)
				.map(|(l_name, l_value)| {
					let mut l = proto::LabelPair::default();
					l.set_name(l_name.to_string());
					l.set_value(l_value.to_string());
					l
				})
				.chain(self.desc.const_label_pairs.iter().cloned())
				.collect::<Vec<_>>());

			counters.push(m);
		});

		let mut m = proto::MetricFamily::default();
		m.set_name(self.desc.fq_name.clone());
		m.set_help(self.desc.help.clone());
		m.set_field_type(T::proto());
		m.set_metric(counters);

		vec![m]
	}
}

/// Types of metrics that can obtain their values from an existing source.
pub trait SourcedType: private::Sealed + Sync + Send {
	#[doc(hidden)]
	fn proto() -> proto::MetricType;
}

impl SourcedType for Counter {
	fn proto() -> proto::MetricType { proto::MetricType::COUNTER }
}

impl SourcedType for Gauge {
	fn proto() -> proto::MetricType { proto::MetricType::GAUGE }
}

mod private {
	pub trait Sealed {}
	impl Sealed for super::Counter {}
	impl Sealed for super::Gauge {}
}