Fix: Graceful Telegram bot shutdown to prevent 409 Conflict (#3580)

* Fix: Graceful Telegram bot shutdown to prevent 409 Conflict

Introduces a `botCancel` context and a global `StopBot()` function to ensure the Telegram bot's Long Polling operation is safely terminated (via context cancellation) before the service restarts. This prevents the "Conflict: another update consumer is running" (409) error upon panel restart.

Changes:
- Added `botCancel context.CancelFunc` to manage context cancellation.
- Implemented global `StopBot()` function.
- Updated `Tgbot.Stop()` to call `StopBot()`.
- Modified `Tgbot.OnReceive()` to use the new cancellable context for `UpdatesViaLongPolling`.

* Fix: Prevent race condition and goroutine leak in TgBot

Addresses a critical race condition on the global `botCancel` variable, which could occur if `Tgbot.OnReceive()` was called concurrently (e.g., during rapid panel restarts or unexpected behavior).

Changes in tgbot.go:
- Added `tgBotMutex sync.Mutex` to ensure thread safety.
- Protected `botCancel` creation and assignment in `OnReceive()` using the mutex, and added a check to prevent overwriting an active context, which avoids goroutine leaks.
- Protected the cancellation and cleanup logic in `StopBot()` with the mutex.

* Refactor: Replace time.Sleep with sync.WaitGroup for reliable TgBot shutdown

Replaced the unreliable `time.Sleep(1 * time.Second)` in `service.StopBot()` with `sync.WaitGroup`. This ensures the Long Polling goroutine is explicitly waited for and reliably exits before the panel continues, preventing potential resource leaks and incomplete shutdowns during restarts.

Changes:
- Added `botWG sync.WaitGroup` variable.
- Updated `service.StopBot()` to call `botWG.Wait()` instead of `time.Sleep()`.
- Modified `Tgbot.OnReceive()` to correctly use `botWG.Add(1)` and `defer botWG.Done()` within the Long Polling goroutine.
- Corrected the goroutine structure in `OnReceive()` to properly encapsulate all message handling logic.

web/service/tgbot.go

@@ -39,6 +39,14 @@ import (
 
 var (
 	bot *telego.Bot
+
+	// botCancel stores the function to cancel the context, stopping Long Polling gracefully.
+	botCancel context.CancelFunc
+	// tgBotMutex protects concurrent access to botCancel variable
+	tgBotMutex sync.Mutex
+	// botWG waits for the OnReceive Long Polling goroutine to finish.
+	botWG sync.WaitGroup
+
 	botHandler  *th.BotHandler
 	adminIds    []int64
 	isRunning   bool
@@ -306,8 +314,13 @@ func (t *Tgbot) SetHostname() {
 	hostname = host
 }
 
-// Stop stops the Telegram bot and cleans up resources.
+// Stop safely stops the Telegram bot's Long Polling operation.
+// This method now calls the global StopBot function and cleans up other resources.
 func (t *Tgbot) Stop() {
+	// Call the global StopBot function to gracefully shut down Long Polling
+	StopBot()
+
+	// Stop the bot handler (in case the goroutine hasn't exited yet)
 	if botHandler != nil {
 		botHandler.Stop()
 	}
@@ -316,6 +329,27 @@ func (t *Tgbot) Stop() {
 	adminIds = nil
 }
 
+// StopBot safely stops the Telegram bot's Long Polling operation by cancelling its context.
+// This is the global function called from main.go's signal handler and t.Stop().
+func StopBot() {
+	tgBotMutex.Lock()
+	defer tgBotMutex.Unlock()
+
+	if botCancel != nil {
+		logger.Info("Sending cancellation signal to Telegram bot...")
+
+		// Calling botCancel() cancels the context passed to UpdatesViaLongPolling,
+		// which stops the Long Polling operation and closes the updates channel,
+		// allowing the th.Start() goroutine to exit cleanly.
+		botCancel()
+
+		botCancel = nil
+		// Giving the goroutine a small delay to exit cleanly.
+		botWG.Wait()
+		logger.Info("Telegram bot successfully stopped.")
+	}
+}
+
 // encodeQuery encodes the query string if it's longer than 64 characters.
 func (t *Tgbot) encodeQuery(query string) string {
 	// NOTE: we only need to hash for more than 64 chars
@@ -345,11 +379,29 @@ func (t *Tgbot) OnReceive() {
 	params := telego.GetUpdatesParams{
 		Timeout: 30, // Increased timeout to reduce API calls
 	}
+	// --- GRACEFUL SHUTDOWN FIX: Context creation ---
+	tgBotMutex.Lock()
 
-	updates, _ := bot.UpdatesViaLongPolling(context.Background(), &params)
+	// Create a context with cancellation and store the cancel function.
+	var ctx context.Context
+
+	// Check if botCancel is already set (to prevent race condition overwrite and goroutine leak)
+	if botCancel == nil {
+		ctx, botCancel = context.WithCancel(context.Background())
+	} else {
+		// If botCancel is already set, use a non-cancellable context for this redundant call.
+		// This prevents overwriting the active botCancel and causing a goroutine leak from the previous call.
+		logger.Warning("TgBot OnReceive called concurrently. Using background context for redundant call.")
+		ctx = context.Background() // <<< ИЗМЕНЕНИЕ
+	}
+
+	tgBotMutex.Unlock()
+
+	// Get updates channel using the context.
+	updates, _ := bot.UpdatesViaLongPolling(ctx, &params)
+	botWG.Go(func() {
 
 		botHandler, _ = th.NewBotHandler(bot, updates)
-
 		botHandler.HandleMessage(func(ctx *th.Context, message telego.Message) error {
 			delete(userStates, message.Chat.ID)
 			t.SendMsgToTgbot(message.Chat.ID, t.I18nBot("tgbot.keyboardClosed"), tu.ReplyKeyboardRemove())
@@ -527,6 +579,7 @@ func (t *Tgbot) OnReceive() {
 		}, th.AnyMessage())
 
 		botHandler.Start()
+	})
 }
 
 // answerCommand processes incoming command messages from Telegram users.