fastmetrics

A pure-Rust implementation of the OpenMetrics specification for transmitting cloud-native metrics at scale, and it's compatible with Prometheus.

Features

• Full support for OpenMetrics specification
• Fast encoding in both text and (optional) protobuf exposition format
• Customizable metric types (currently a set of commonly used metric types are provided)
• Hierarchical metric organization with namespaces and subsystems
• Support for variable and constant labels
• Derive macros to simplify code (e.g., like registering metrics, label handling, etc.)

Usage

use fastmetrics::{
    encoder::{EncodeLabelSet, EncodeLabelValue},
    format::text,
    metrics::{counter::Counter, family::Family},
    registry::{Register, Registry},
};

// Define label types
// Need to enable `derive` feature to use `#[derive(EncodeLabelSet)]`
#[derive(Clone, Eq, PartialEq, Hash, EncodeLabelSet)]
struct Labels {
    method: Method,
    status: u16,
}

// Need to enable `derive` feature to use `#[derive(EncodeLabelValue)]`
#[derive(Clone, Eq, PartialEq, Hash, EncodeLabelValue)]
enum Method {
    Get,
    Put,
}

// Need to enable `derive` feature to use `#[derive(Register)]`
#[derive(Default, Register)]
struct Metrics {
    /// Total requests processed
    requests: Counter,
    /// Total HTTP requests
    http_requests: Family<Labels, Counter>,
}

fn main() -> Box<dyn std::error::Error> {
    // Create a registry with a namespace and some constant labels
    let mut registry = Registry::builder()
        .with_namespace("myapp")
        .with_const_labels([("env", "prod")])
        .build();

    // Register metrics
    let metrics = Metrics::default();
    metrics.register(&mut registry)?;

    // Update the simple counter
    metrics.requests.inc();
    assert_eq!(metrics.requests.total(), 1);

    // Update the counter family
    let labels = Labels { method: Method::Get, status: 200 };
    metrics.http_requests.with_or_new(&labels, |req| req.inc());
    assert_eq!(metrics.http_requests.with(&labels, |req| req.total()), Some(1));

    // Export metrics in text format
    let mut output = String::new();
    text::encode(&mut output, &registry)?;
    println!("{}", output);

    Ok(())
}

See documentation and examples for more details.

Performance

Compared with the existing rust client libraries, its text encoding is about 20%~30% faster than the fastest rust library (prometheus-client), while its Protobuf encoding is on par with the fastest rust library (prometheus).

See benchmarks for more details

Acknowledgment

I drew a lot of inspiration from the following libraries, retaining the designs I thought were good and experimenting with some different ones.

• prometheus/client_golang: Official prometheus client library for Golang applications.
• prometheus/client_rust: Official prometheus client library for Rust applications.
• tikv/rust-prometheus: Another prometheus instrumentation library for Rust applications.

License

This project is licensed under the Apache License, Version 2.0 - see the LICENSE file for details.