prometheus_endpoint/
sourced.rs

1// This file is part of Tetcore.
2
3// Copyright (C) 2020-2021 Parity Technologies (UK) Ltd.
4// SPDX-License-Identifier: Apache-2.0
5
6// Licensed under the Apache License, Version 2.0 (the "License");
7// you may not use this file except in compliance with the License.
8// You may obtain a copy of the License at
9//
10// 	http://www.apache.org/licenses/LICENSE-2.0
11//
12// Unless required by applicable law or agreed to in writing, software
13// distributed under the License is distributed on an "AS IS" BASIS,
14// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15// See the License for the specific language governing permissions and
16// limitations under the License.
17
18//! Metrics that are collected from existing sources.
19
20use prometheus::core::{Collector, Desc, Describer, Number, Opts};
21use prometheus::proto;
22use std::{cmp::Ordering, marker::PhantomData};
23
24/// A counter whose values are obtained from an existing source.
25///
26/// > **Note*: The counter values provided by the source `S`
27/// > must be monotonically increasing. Otherwise use a
28/// > [`SourcedGauge`] instead.
29pub type SourcedCounter<S> = SourcedMetric<Counter, S>;
30
31/// A gauge whose values are obtained from an existing source.
32pub type SourcedGauge<S> = SourcedMetric<Gauge, S>;
33
34/// The type of a sourced counter.
35#[derive(Copy, Clone)]
36pub enum Counter {}
37
38/// The type of a sourced gauge.
39#[derive(Copy, Clone)]
40pub enum Gauge {}
41
42/// A metric whose values are obtained from an existing source,
43/// instead of being independently recorded.
44#[derive(Debug, Clone)]
45pub struct SourcedMetric<T, S> {
46	source: S,
47	desc: Desc,
48	_type: PhantomData<T>,
49}
50
51/// A source of values for a [`SourcedMetric`].
52pub trait MetricSource: Sync + Send + Clone {
53	/// The type of the collected values.
54	type N: Number;
55	/// Collects the current values of the metrics from the source.
56	fn collect(&self, set: impl FnMut(&[&str], Self::N));
57}
58
59impl<T: SourcedType, S: MetricSource> SourcedMetric<T, S> {
60	/// Creates a new metric that obtains its values from the given source.
61	pub fn new(opts: &Opts, source: S) -> prometheus::Result<Self> {
62		let desc = opts.describe()?;
63		Ok(Self { source, desc, _type: PhantomData })
64	}
65}
66
67impl<T: SourcedType, S: MetricSource> Collector for SourcedMetric<T, S> {
68	fn desc(&self) -> Vec<&Desc> {
69		vec![&self.desc]
70	}
71
72	fn collect(&self) -> Vec<proto::MetricFamily> {
73		let mut counters = Vec::new();
74
75		self.source.collect(|label_values, value| {
76			let mut m = proto::Metric::default();
77
78			match T::proto() {
79				proto::MetricType::COUNTER => {
80					let mut c = proto::Counter::default();
81					c.set_value(value.into_f64());
82					m.set_counter(c);
83				}
84				proto::MetricType::GAUGE => {
85					let mut g = proto::Gauge::default();
86					g.set_value(value.into_f64());
87					m.set_gauge(g);
88				}
89				t => {
90					log::error!("Unsupported sourced metric type: {:?}", t);
91				}
92			}
93
94			debug_assert_eq!(self.desc.variable_labels.len(), label_values.len());
95			match self.desc.variable_labels.len().cmp(&label_values.len()) {
96				Ordering::Greater =>
97					log::warn!("Missing label values for sourced metric {}", self.desc.fq_name),
98				Ordering::Less =>
99					log::warn!("Too many label values for sourced metric {}", self.desc.fq_name),
100				Ordering::Equal => {}
101			}
102
103			m.set_label(self.desc.variable_labels.iter().zip(label_values)
104				.map(|(l_name, l_value)| {
105					let mut l = proto::LabelPair::default();
106					l.set_name(l_name.to_string());
107					l.set_value(l_value.to_string());
108					l
109				})
110				.chain(self.desc.const_label_pairs.iter().cloned())
111				.collect::<Vec<_>>());
112
113			counters.push(m);
114		});
115
116		let mut m = proto::MetricFamily::default();
117		m.set_name(self.desc.fq_name.clone());
118		m.set_help(self.desc.help.clone());
119		m.set_field_type(T::proto());
120		m.set_metric(counters);
121
122		vec![m]
123	}
124}
125
126/// Types of metrics that can obtain their values from an existing source.
127pub trait SourcedType: private::Sealed + Sync + Send {
128	#[doc(hidden)]
129	fn proto() -> proto::MetricType;
130}
131
132impl SourcedType for Counter {
133	fn proto() -> proto::MetricType { proto::MetricType::COUNTER }
134}
135
136impl SourcedType for Gauge {
137	fn proto() -> proto::MetricType { proto::MetricType::GAUGE }
138}
139
140mod private {
141	pub trait Sealed {}
142	impl Sealed for super::Counter {}
143	impl Sealed for super::Gauge {}
144}
prometheus_endpoint/sourced.rs

prometheus_endpoint/
sourced.rs
