Torjus Håkestad
bc02393c5a
After a successful switch deployment, the listener now waits for Prometheus to scrape the /metrics endpoint before exiting for restart. This ensures deployment metrics are captured before the process restarts and resets in-memory counters. Falls back to a 60 second timeout if no scrape occurs. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
103 lines
2.4 KiB
Go
103 lines
2.4 KiB
Go
package metrics
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import (
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"context"
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"fmt"
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"log/slog"
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"net/http"
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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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)
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// ServerConfig holds configuration for the metrics server.
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type ServerConfig struct {
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Addr string
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Logger *slog.Logger
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}
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// Server serves Prometheus metrics over HTTP.
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type Server struct {
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httpServer *http.Server
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registry *prometheus.Registry
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collector *Collector
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logger *slog.Logger
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scrapeCh chan struct{}
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}
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// NewServer creates a new metrics server.
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func NewServer(cfg ServerConfig) *Server {
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logger := cfg.Logger
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if logger == nil {
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logger = slog.Default()
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}
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registry := prometheus.NewRegistry()
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collector := NewCollector(registry)
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scrapeCh := make(chan struct{})
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metricsHandler := promhttp.HandlerFor(registry, promhttp.HandlerOpts{
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Registry: registry,
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})
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mux := http.NewServeMux()
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mux.Handle("/metrics", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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metricsHandler.ServeHTTP(w, r)
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// Signal that a scrape occurred (non-blocking)
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select {
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case scrapeCh <- struct{}{}:
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default:
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}
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}))
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mux.HandleFunc("/health", func(w http.ResponseWriter, _ *http.Request) {
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w.WriteHeader(http.StatusOK)
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_, _ = w.Write([]byte("ok"))
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})
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return &Server{
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httpServer: &http.Server{
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Addr: cfg.Addr,
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Handler: mux,
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ReadHeaderTimeout: 10 * time.Second,
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},
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registry: registry,
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collector: collector,
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logger: logger,
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scrapeCh: scrapeCh,
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}
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}
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// Collector returns the metrics collector.
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func (s *Server) Collector() *Collector {
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return s.collector
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}
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// ScrapeCh returns a channel that receives a signal each time the metrics endpoint is scraped.
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func (s *Server) ScrapeCh() <-chan struct{} {
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return s.scrapeCh
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}
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// Start starts the HTTP server in a goroutine.
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func (s *Server) Start() error {
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s.logger.Info("starting metrics server", "addr", s.httpServer.Addr)
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go func() {
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if err := s.httpServer.ListenAndServe(); err != nil && err != http.ErrServerClosed {
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s.logger.Error("metrics server error", "error", err)
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}
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}()
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return nil
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}
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// Shutdown gracefully shuts down the server.
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func (s *Server) Shutdown(ctx context.Context) error {
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s.logger.Info("shutting down metrics server")
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if err := s.httpServer.Shutdown(ctx); err != nil {
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return fmt.Errorf("failed to shutdown metrics server: %w", err)
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}
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return nil
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}
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