feat: add graceful shutdown (#285)

With this commit, the backend will stop accepting new connections on SIGINT or SIGTERM,
but allow existing requests to finish. This graceful shutdown has a timeout of
25 seconds.

Additionally, this removes the double timestamp from the production log format.

Author: morremeyer

internal/router/router.go

@@ -121,8 +121,6 @@ func Router() (*gin.Engine, error) {
 	controllers.RegisterEnvelopeRoutes(v1.Group("/envelopes"))
 	controllers.RegisterAllocationRoutes(v1.Group("/allocations"))
 
-	log.Info().Msg("backend startup complete")
-
 	return r, nil
 }
 

main.go

@@ -1,9 +1,14 @@
 package main
 
 import (
+	"context"
 	"io"
+	"net/http"
 	"os"
+	"os/signal"
 	"path/filepath"
+	"syscall"
+	"time"
 
 	"github.com/envelope-zero/backend/internal/database"
 	"github.com/envelope-zero/backend/internal/router"
@@ -37,7 +42,7 @@ func main() {
 	if gin.IsDebugging() {
 		zerolog.SetGlobalLevel(zerolog.DebugLevel)
 	}
-	log.Logger = log.Output(output).With().Timestamp().Logger()
+	log.Logger = log.Output(output).With().Logger()
 
 	// Create data directory
 	dataDir := filepath.Join(".", "data")
@@ -70,7 +75,39 @@ func main() {
 		log.Fatal().Msg(err.Error())
 	}
 
-	if err := r.Run(); err != nil {
-		log.Fatal().Msg(err.Error())
+	// Set the port to the env variable, default to 8080
+	var port string
+	if port = os.Getenv("PORT"); port == "" {
+		port = ":8080"
+	}
+
+	// The following code is taken from https://github.com/gin-gonic/examples/blob/91fb0d925b3935d2c6e4d9336d78cf828925789d/graceful-shutdown/graceful-shutdown/notify-without-context/server.go
+	// and has been modified to not wait for the
+	srv := &http.Server{
+		Addr:    port,
+		Handler: r,
+	}
+
+	// Wait for interrupt signal to gracefully shutdown the server with a timeout of 5 seconds.
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)
+
+	go func() {
+		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			log.Fatal().Str("event", "Error during startup").Err(err).Msg("Router")
+		}
+	}()
+	log.Info().Str("event", "Startup complete").Msg("Router")
+
+	<-quit
+	log.Info().Str("event", "Received SIGINT or SIGTERM, stopping gracefully with 25 seconds timeout").Msg("Router")
+
+	// Create a context with a 25 second timeout for the server to shut down in
+	ctx, cancel := context.WithTimeout(context.Background(), 25*time.Second)
+	defer cancel()
+
+	if err := srv.Shutdown(ctx); err != nil {
+		log.Fatal().Str("event", "Graceful shutdown failed, terminating").Err(err).Msg("Router")
 	}
+	log.Info().Str("event", "Backend stopped").Msg("Router")
 }