Lux Metrics Library

github.com/luxfi/metric is the native metrics library for Lux. It produces a scrape-compatible text exposition format and is designed for low overhead in hot paths.

Features

• Single, native API for counters, gauges, histograms, summaries, and vectors
• Scrape-compatible text format encoder and HTTP handler
• Registry + gatherer model for composition
• Optional no-op build for benchmark runs (build-tagged swap)

Installation

go get github.com/luxfi/metric@latest

Quick Start

package main

import (
	"net/http"

	"github.com/luxfi/metric"
)

func main() {
	m := metric.New("myapp")

	requests := m.NewCounter("requests_total", "Total requests")
	latency := m.NewHistogram("request_seconds", "Request latency (s)", metric.DefBuckets)

	requests.Inc()
	latency.Observe(0.123)

	http.Handle("/metrics", metric.Handler())
	_ = http.ListenAndServe(":8080", nil)
}

Custom Registry

reg := metric.NewRegistry()
m := metric.NewWithRegistry("myapp", reg)

requests := m.NewCounter("requests_total", "Total requests")
requests.Inc()

handler := metric.NewHTTPHandler(reg, metric.HandlerOpts{})

Vector Metrics

m := metric.New("myapp")
byRoute := m.NewCounterVec("requests_total", "Requests by route", []string{"method", "route"})

byRoute.WithLabelValues("GET", "/").Inc()

Metrics Off Build

For benchmark runs, you can swap the entire package to no-op implementations using build tags. This keeps call sites unchanged while minimizing overhead.

go test -tags metrics ./...

When built without the metrics tag, metric.NewRegistry() and the package defaults return no-op implementations. Pre-bind label values in hot paths to avoid argument construction overhead.