88 lines
2.3 KiB
Go
88 lines
2.3 KiB
Go
// Package metricsserver provides a standalone HTTP server for exposing Prometheus metrics.
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//
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// This package implements a dedicated metrics server that exposes application metrics
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// via HTTP. It uses a custom Prometheus registry to avoid conflicts with other metric
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// collectors and provides graceful shutdown capabilities.
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package metricsserver
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import (
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"context"
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"net/http"
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"strconv"
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"time"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/client_golang/prometheus/promhttp"
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"golang.org/x/sync/errgroup"
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"go.ntppool.org/common/logger"
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)
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// Metrics provides a custom Prometheus registry and HTTP handlers for metrics exposure.
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// It isolates application metrics from the default global registry.
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type Metrics struct {
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r *prometheus.Registry
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}
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// New creates a new Metrics instance with a custom Prometheus registry.
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func New() *Metrics {
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r := prometheus.NewRegistry()
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m := &Metrics{
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r: r,
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}
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return m
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}
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// Registry returns the custom Prometheus registry.
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// Use this to register your application's metrics collectors.
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func (m *Metrics) Registry() *prometheus.Registry {
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return m.r
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}
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// Handler returns an HTTP handler for the /metrics endpoint with OpenMetrics support.
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func (m *Metrics) Handler() http.Handler {
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log := logger.NewStdLog("prom http", false, nil)
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return promhttp.HandlerFor(m.r, promhttp.HandlerOpts{
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ErrorLog: log,
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Registry: m.r,
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EnableOpenMetrics: true,
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})
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}
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// ListenAndServe starts a metrics server on the specified port and blocks until ctx is done.
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// The server exposes the metrics handler and shuts down gracefully when the context is cancelled.
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func (m *Metrics) ListenAndServe(ctx context.Context, port int) error {
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log := logger.Setup()
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srv := &http.Server{
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Addr: ":" + strconv.Itoa(port),
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ReadTimeout: 10 * time.Second,
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WriteTimeout: 20 * time.Second,
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IdleTimeout: 120 * time.Second,
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Handler: m.Handler(),
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}
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g, ctx := errgroup.WithContext(ctx)
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g.Go(func() error {
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err := srv.ListenAndServe()
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if err != nil && err != http.ErrServerClosed {
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log.Warn("metrics server done listening", "err", err)
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return err
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}
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return nil
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})
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<-ctx.Done()
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if err := srv.Shutdown(ctx); err != nil {
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log.Error("metrics server shutdown failed", "err", err)
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return err
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}
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return g.Wait()
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}
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