gochat/backend/internal/app/shutdown.go

package app

import (
	"context"
	"os"
	"os/signal"
	"syscall"
	"time"

	applogger "github.com/gochat/gochat/pkg/logger"
)

// Shutdown handles graceful shutdown of the application.
// Pattern follows Chatwoot's Puma graceful shutdown (config/puma.rb)
// and Rails signal handling (SIGTERM -> graceful stop).
// Order: 1. Stop accepting new connections (done by http.Server.Shutdown in main)
//        2. Stop config hot-reloader
//        3. Close notification delivery service (Watermill router + subscriber)
//        4. Close WebSocket Hub (disconnect all clients)
//        5. Close PubSub (stop message publishing/consuming)
//        6. Close database connection pool
//        7. Flush logger buffers
func (a *App) Shutdown(timeout time.Duration) error {
	start := time.Now()
	applogger.L().Info("Shutting down GoChat application...")

	// Step 0: Stop config hot-reloader
	if a.reloader != nil {
		a.reloader.Stop()
		applogger.L().Info("Config hot-reloader stopped")
	}

	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	// Step 0.5: Close notification delivery service (Watermill router + subscriber)
	if a.notificationDeliverySvc != nil {
		if closeErr := a.notificationDeliverySvc.Close(); closeErr != nil {
			applogger.L().Errorf("Notification delivery service close error: %v", closeErr)
		} else {
			applogger.L().Info("Notification delivery service closed")
		}
	}

	// Step 1: Close WebSocket Hub — disconnect all connected clients
	if a.wsHub != nil {
		a.wsHub.Shutdown(ctx)
		applogger.L().Info("WebSocket hub closed")
	}

	// Step 2: Close PubSub — stop event publishing and consuming
	if a.pubsub != nil {
		if closer, ok := a.pubsub.(interface{ Close() error }); ok {
			if closeErr := closer.Close(); closeErr != nil {
				applogger.L().Errorf("PubSub close error: %v", closeErr)
			} else {
				applogger.L().Info("PubSub closed")
			}
		}
	}

	// Step 3: Close database connection pool
	if a.db != nil {
		sqlDB, err := a.db.DB()
		if err == nil {
			if closeErr := sqlDB.Close(); closeErr != nil {
				applogger.L().Errorf("Database close error: %v", closeErr)
			} else {
				applogger.L().Info("Database connection pool closed")
			}
		}
	}

	// Step 4: Flush logger buffer
	applogger.Sync()

	duration := time.Since(start)
	applogger.L().Infof("GoChat shutdown complete (took %v)", duration)

	return nil
}

// WaitForShutdownSignal blocks until a termination signal is received.
func WaitForShutdownSignal() {
	quit := make(chan os.Signal, 1)
	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
	<-quit
	applogger.L().Info("Received shutdown signal")
}