flagger/pkg/server/server.go

package server

import (
	"context"
	"net/http"
	"time"

	"github.com/prometheus/client_golang/prometheus/promhttp"
	"go.uber.org/zap"
)

// ListenAndServe starts a web server and waits for SIGTERM
func ListenAndServe(port string, timeout time.Duration, logger *zap.SugaredLogger, stopCh <-chan struct{}) {
	mux := http.DefaultServeMux
	mux.Handle("/metrics", promhttp.Handler())
	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
		w.Write([]byte("OK"))
	})

	srv := &http.Server{
		Addr:         ":" + port,
		Handler:      mux,
		ReadTimeout:  5 * time.Second,
		WriteTimeout: 1 * time.Minute,
		IdleTimeout:  15 * time.Second,
	}

	logger.Infof("Starting HTTP server on port %s", port)

	// run server in background
	go func() {
		if err := srv.ListenAndServe(); err != http.ErrServerClosed {
			logger.Fatalf("HTTP server crashed %v", err)
		}
	}()

	// wait for SIGTERM or SIGINT
	<-stopCh
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	if err := srv.Shutdown(ctx); err != nil {
		logger.Errorf("HTTP server graceful shutdown failed %v", err)
	} else {
		logger.Info("HTTP server stopped")
	}
}