我对现有的 prometheus library: prometheus 和 prometheus-client 的一些设计不太满意, 所以从今年年初开始抽空自己实现了一个 library，暴露的API设计接近 prometheus-client，现阶段在公司内部产品中也使用了一段时间，如果你有这方面需求的话，也许可以考虑尝试下，如果能有一些使用反馈提供给我的话就更好了。

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(())
}