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
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171

// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

mod sourced;

use hyper::{http::StatusCode, Request, Response};
use prometheus::{core::Collector, Encoder, TextEncoder};
use std::net::SocketAddr;

pub use prometheus::{
	self,
	core::{
		AtomicF64 as F64, AtomicI64 as I64, AtomicU64 as U64, GenericCounter as Counter,
		GenericCounterVec as CounterVec, GenericGauge as Gauge, GenericGaugeVec as GaugeVec,
	},
	exponential_buckets, Error as PrometheusError, Histogram, HistogramOpts, HistogramVec, Opts,
	Registry,
};
pub use sourced::{MetricSource, SourcedCounter, SourcedGauge, SourcedMetric};

type Body = http_body_util::Full<hyper::body::Bytes>;

pub fn register<T: Clone + Collector + 'static>(
	metric: T,
	registry: &Registry,
) -> Result<T, PrometheusError> {
	registry.register(Box::new(metric.clone()))?;
	Ok(metric)
}

#[derive(Debug, thiserror::Error)]
pub enum Error {
	/// Hyper internal error.
	#[error(transparent)]
	Hyper(#[from] hyper::Error),

	/// Http request error.
	#[error(transparent)]
	Http(#[from] hyper::http::Error),

	/// i/o error.
	#[error(transparent)]
	Io(#[from] std::io::Error),

	#[error("Prometheus port {0} already in use.")]
	PortInUse(SocketAddr),
}

async fn request_metrics(
	req: Request<hyper::body::Incoming>,
	registry: Registry,
) -> Result<Response<Body>, Error> {
	if req.uri().path() == "/metrics" {
		let metric_families = registry.gather();
		let mut buffer = vec![];
		let encoder = TextEncoder::new();
		encoder.encode(&metric_families, &mut buffer).unwrap();

		Response::builder()
			.status(StatusCode::OK)
			.header("Content-Type", encoder.format_type())
			.body(Body::from(buffer))
			.map_err(Error::Http)
	} else {
		Response::builder()
			.status(StatusCode::NOT_FOUND)
			.body(Body::from("Not found."))
			.map_err(Error::Http)
	}
}

/// Initializes the metrics context, and starts an HTTP server
/// to serve metrics.
pub async fn init_prometheus(prometheus_addr: SocketAddr, registry: Registry) -> Result<(), Error> {
	let listener = tokio::net::TcpListener::bind(&prometheus_addr).await.map_err(|e| {
		log::error!(target: "prometheus", "Error binding to '{:#?}': {:#?}", prometheus_addr, e);
		Error::PortInUse(prometheus_addr)
	})?;

	init_prometheus_with_listener(listener, registry).await
}

/// Init prometheus using the given listener.
async fn init_prometheus_with_listener(
	listener: tokio::net::TcpListener,
	registry: Registry,
) -> Result<(), Error> {
	log::info!(target: "prometheus", "〽️ Prometheus exporter started at {}", listener.local_addr()?);

	let server = hyper_util::server::conn::auto::Builder::new(hyper_util::rt::TokioExecutor::new());

	loop {
		let io = match listener.accept().await {
			Ok((sock, _)) => hyper_util::rt::TokioIo::new(sock),
			Err(e) => {
				log::debug!(target: "prometheus", "Error accepting connection: {:?}", e);
				continue;
			},
		};

		let registry = registry.clone();

		let conn = server
			.serve_connection_with_upgrades(
				io,
				hyper::service::service_fn(move |req| request_metrics(req, registry.clone())),
			)
			.into_owned();

		tokio::spawn(async move {
			if let Err(err) = conn.await {
				log::debug!(target: "prometheus", "connection error: {:?}", err);
			}
		});
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use http_body_util::BodyExt;
	use hyper::Uri;
	use hyper_util::{client::legacy::Client, rt::TokioExecutor};

	const METRIC_NAME: &str = "test_test_metric_name_test_test";

	#[tokio::test]
	async fn prometheus_works() {
		let listener =
			tokio::net::TcpListener::bind("127.0.0.1:0").await.expect("Creates listener");

		let local_addr = listener.local_addr().expect("Returns the local addr");

		let registry = Registry::default();
		register(
			prometheus::Counter::new(METRIC_NAME, "yeah").expect("Creates test counter"),
			&registry,
		)
		.expect("Registers the test metric");

		tokio::spawn(init_prometheus_with_listener(listener, registry));

		let client = Client::builder(TokioExecutor::new()).build_http::<Body>();

		let res = client
			.get(Uri::try_from(&format!("http://{}/metrics", local_addr)).expect("Parses URI"))
			.await
			.expect("Requests metrics");

		assert!(res.status().is_success());

		let buf = res.into_body().collect().await.expect("Failed to read HTTP body").to_bytes();
		let body = String::from_utf8(buf.to_vec()).expect("Converts body to String");

		assert!(body.contains(&format!("{} 0", METRIC_NAME)));
	}
}