prometheus

metrics/processors/prometheus

Import path: github.com/InsideGallery/core/metrics/processors/prometheus

This package registers the Prometheus metrics processor. It records metrics in an in-process Prometheus registry and exposes the active registry through HTTPHandler.

Main APIs

• ProcessorName is the registration name: prometheus.
• New(cfg metrics.Config, service string) creates the processor and is registered from init.
• HTTPHandler(w http.ResponseWriter, r *http.Request) serves the active scrape response.

Usage

package main

import (
	"net/http"

	_ "github.com/InsideGallery/core/metrics/processors/prometheus"

	"github.com/InsideGallery/core/metrics"
	"github.com/InsideGallery/core/metrics/processors/prometheus"
)

func newMetrics() (*metrics.Client, error) {
	cfg, err := metrics.GetEnvConfig()
	if err != nil {
		return nil, err
	}

	http.HandleFunc("/metrics", prometheus.HTTPHandler)

	return metrics.New(cfg, "api")
}

METRICS_PROCESSORS defaults to prometheus, but the processor package still has to be imported directly or through metrics/all so it can register itself.

Configuration

The package reads the METRICS_PROMETHEUS prefix for histogram tuning:

• METRICS_PROMETHEUS_CLASSIC_BUCKETS: comma-separated finite positive bucket values, sorted and de-duplicated.
• METRICS_PROMETHEUS_NATIVE_BUCKET_FACTOR: native histogram bucket factor, default 1.1; must be greater than 1.
• METRICS_PROMETHEUS_NATIVE_ZERO_THRESHOLD: default 0.
• METRICS_PROMETHEUS_NATIVE_MAX_BUCKETS: default 160.
• METRICS_PROMETHEUS_NATIVE_MIN_RESET_DURATION: default 1h.
• METRICS_PROMETHEUS_NATIVE_MAX_ZERO_THRESHOLD: default 0.

Operational Notes

New registers Go runtime and process collectors with a constant service label, then makes that processor active for HTTPHandler. The latest created processor is active. Closing an inactive processor does not clear the active one; closing the active processor clears it.

Counts become counters and reject negative values. Gauges become gauges. Distributions become histograms. Tags in key:value form become labels after normalization and sanitization; loose tags are ignored by this processor. When no processor is active, HTTPHandler returns 200 OK with an empty Prometheus text response.