From ae39203d95da4d94647b36cc1713276c6f216aa9 Mon Sep 17 00:00:00 2001
From: nuxen <theonenuxen@proton.me>
Date: Sat, 24 Feb 2024 18:57:45 +0100
Subject: [PATCH] feat(http): implement graceful shutdown

---
 cmd/seasonpackarr/main.go   | 22 +++++++++++++++++++---
 internal/http/middleware.go |  2 +-
 internal/http/server.go     | 20 +++++++++++++++-----
 3 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/cmd/seasonpackarr/main.go b/cmd/seasonpackarr/main.go
index e422c6f..0e9c3e7 100644
--- a/cmd/seasonpackarr/main.go
+++ b/cmd/seasonpackarr/main.go
@@ -4,6 +4,7 @@
 package main
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	netHTTP "net/http"
@@ -125,16 +126,31 @@ func main() {
 
 		errorChannel := make(chan error)
 		go func() {
-			errorChannel <- srv.Open()
+			err := srv.Open()
+			if err != nil {
+				if !errors.Is(err, http.ErrServerClosed) {
+					errorChannel <- err
+				}
+			}
 		}()
 
 		sigCh := make(chan os.Signal, 1)
 		signal.Notify(sigCh, syscall.SIGHUP, syscall.SIGINT, syscall.SIGQUIT, syscall.SIGTERM)
 
-		for sig := range sigCh {
-			log.Info().Msgf("received signal: %v, shutting down server.", sig)
+		select {
+		case sig := <-sigCh:
+			log.Info().Msgf("received signal: %q, shutting down server.", sig.String())
 			os.Exit(0)
+
+		case err := <-errorChannel:
+			log.Error().Err(err).Msg("unexpected error from server")
 		}
+		if err := srv.Shutdown(context.Background()); err != nil {
+			log.Error().Err(err).Msg("error during http shutdown")
+			os.Exit(1)
+		}
+
+		os.Exit(0)
 
 	default:
 		pflag.Usage()
diff --git a/internal/http/middleware.go b/internal/http/middleware.go
index 0b280b7..b62bc72 100644
--- a/internal/http/middleware.go
+++ b/internal/http/middleware.go
@@ -6,7 +6,7 @@ package http
 
 import "net/http"
 
-func (s Server) isAuthenticated(next http.Handler) http.Handler {
+func (s *Server) isAuthenticated(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		// allow access if apiToken value is set to an empty string
 		if s.cfg.Config.APIToken == "" {
diff --git a/internal/http/server.go b/internal/http/server.go
index 6eb32ec..7568679 100644
--- a/internal/http/server.go
+++ b/internal/http/server.go
@@ -5,6 +5,7 @@
 package http
 
 import (
+	"context"
 	"fmt"
 	"net"
 	"net/http"
@@ -17,9 +18,13 @@ import (
 	"github.com/go-chi/chi/v5/middleware"
 )
 
+var ErrServerClosed = http.ErrServerClosed
+
 type Server struct {
 	log logger.Logger
 	cfg *config.AppConfig
+
+	httpServer http.Server
 }
 
 func NewServer(log logger.Logger, config *config.AppConfig) *Server {
@@ -29,7 +34,7 @@ func NewServer(log logger.Logger, config *config.AppConfig) *Server {
 	}
 }
 
-func (s Server) Open() error {
+func (s *Server) Open() error {
 	addr := fmt.Sprintf("%v:%v", s.cfg.Config.Host, s.cfg.Config.Port)
 
 	var err error
@@ -44,7 +49,7 @@ func (s Server) Open() error {
 	return err
 }
 
-func (s Server) tryToServe(addr, proto string) error {
+func (s *Server) tryToServe(addr, proto string) error {
 	listener, err := net.Listen(proto, addr)
 	if err != nil {
 		return err
@@ -52,15 +57,20 @@ func (s Server) tryToServe(addr, proto string) error {
 
 	s.log.Info().Msgf("Starting %s server. Listening on %s", proto, listener.Addr().String())
 
-	server := http.Server{
+	s.httpServer = http.Server{
 		Handler:           s.Handler(),
 		ReadHeaderTimeout: time.Second * 15,
 	}
 
-	return server.Serve(listener)
+	return s.httpServer.Serve(listener)
+}
+
+func (s *Server) Shutdown(ctx context.Context) error {
+	s.log.Info().Msgf("shutting down http server gracefully...")
+	return s.httpServer.Shutdown(ctx)
 }
 
-func (s Server) Handler() http.Handler {
+func (s *Server) Handler() http.Handler {
 	r := chi.NewRouter()
 
 	r.Use(middleware.RequestID)