src/polling: Fix the Offset Infinite Loop bug (#265)

References:

  * BR: https://github.com/yagop/node-telegram-bot-api/issues/36

CHANGELOG.md

@@ -26,6 +26,7 @@ Changed:
 
 Fixed:
 
+1. (#265) Fix the offset infinite loop bug (#36) (by @GochoMugo)
 1. Fix game example (by @MCSH)
 
 

doc/api.md

@@ -122,6 +122,7 @@ Emits `message` when a message arrives.
 | [options.request] | <code>Object</code> |  | Options which will be added for all requests to telegram api.  See https://github.com/request/request#requestoptions-callback for more information. |
 | [options.baseApiUrl] | <code>String</code> | <code>https://api.telegram.org</code> | API Base URl; useful for proxying and testing |
 | [options.filepath] | <code>Boolean</code> | <code>true</code> | Allow passing file-paths as arguments when sending files,  such as photos using `TelegramBot#sendPhoto()`. See [usage information][usage-sending-files-performance]  for more information on this option and its consequences. |
+| [options.badRejection] | <code>Boolean</code> | <code>false</code> | Set to `true`  **if and only if** the Node.js version you're using terminates the  process on unhandled rejections. This option is only for  *forward-compatibility purposes*. |
 
 <a name="TelegramBot+on"></a>
 

doc/usage.md

@@ -36,6 +36,7 @@ that emits the following events:
 1. `pre_checkout_query`: Received a new  incoming pre-checkout query
 1. `polling_error`: Error occurred during polling. See [polling errors](#polling-errors).
 1. `webhook_error`: Error occurred handling a webhook request. See [webhook errors](#webhook-errors).
+1. `error`: Unexpected error occurred, usually fatal!
 
 **Tip:** Its much better to listen a specific event rather than on
 `message` in order to stay safe from the content.

src/telegram.js

@@ -174,6 +174,10 @@ class TelegramBot extends EventEmitter {
    * @param {Boolean} [options.filepath=true] Allow passing file-paths as arguments when sending files,
    *  such as photos using `TelegramBot#sendPhoto()`. See [usage information][usage-sending-files-performance]
    *  for more information on this option and its consequences.
+   * @param {Boolean} [options.badRejection=false] Set to `true`
+   *  **if and only if** the Node.js version you're using terminates the
+   *  process on unhandled rejections. This option is only for
+   *  *forward-compatibility purposes*.
    * @see https://core.telegram.org/bots/api
    */
   constructor(token, options = {}) {
@@ -184,6 +188,7 @@ class TelegramBot extends EventEmitter {
     this.options.webHook = (typeof options.webHook === 'undefined') ? false : options.webHook;
     this.options.baseApiUrl = options.baseApiUrl || 'https://api.telegram.org';
     this.options.filepath = (typeof options.filepath === 'undefined') ? true : options.filepath;
+    this.options.badRejection = (typeof options.badRejection === 'undefined') ? false : options.badRejection;
     this._textRegexpCallbacks = [];
     this._replyListenerId = 0;
     this._replyListeners = [];

src/telegramPolling.js

@@ -1,3 +1,4 @@
+const errors = require('./errors');
 const debug = require('debug')('node-telegram-bot-api');
 const deprecate = require('depd')('node-telegram-bot-api');
 const ANOTHER_WEB_HOOK_USED = 409;
@@ -79,6 +80,18 @@ class TelegramBotPolling {
     return !!this._lastRequest;
   }
 
+  /**
+   * Handle error thrown during polling.
+   * @private
+   * @param  {Error} error
+   */
+  _error(error) {
+    if (!this.bot.listeners('polling_error').length) {
+      return console.error('error: [polling_error] %j', error); // eslint-disable-line no-console
+    }
+    return this.bot.emit('polling_error', error);
+  }
+
   /**
    * Invokes polling (with recursion!)
    * @return {Promise} promise of the current request
@@ -93,18 +106,59 @@ class TelegramBotPolling {
         updates.forEach(update => {
           this.options.params.offset = update.update_id + 1;
           debug('updated offset: %s', this.options.params.offset);
-          this.bot.processUpdate(update);
+          try {
+            this.bot.processUpdate(update);
+          } catch (err) {
+            err._processing = true;
+            throw err;
+          }
         });
         return null;
       })
       .catch(err => {
         debug('polling error: %s', err.message);
-        if (this.bot.listeners('polling_error').length) {
+        if (!err._processing) {
-          this.bot.emit('polling_error', err);
+          return this._error(err);
-        } else {
-          console.error('error: [polling_error] %j', err); // eslint-disable-line no-console
         }
-        return null;
+        delete err._processing;
+        /*
+         * An error occured while processing the items,
+         * i.e. in `this.bot.processUpdate()` above.
+         * We need to mark the already-processed items
+         * to avoid fetching them again once the application
+         * is restarted, or moves to next polling interval
+         * (in cases where unhandled rejections do not terminate
+         * the process).
+         * See https://github.com/yagop/node-telegram-bot-api/issues/36#issuecomment-268532067
+         */
+        if (!this.bot.options.badRejection) {
+          return this._error(err);
+        }
+        const opts = {
+          offset: this.options.params.offset,
+          limit: 1,
+          timeout: 0,
+        };
+        return this.bot.getUpdates(opts).then(() => {
+          return this._error(err);
+        }).catch(requestErr => {
+          /*
+           * We have been unable to handle this error.
+           * We have to log this to stderr to ensure devops
+           * understands that they may receive already-processed items
+           * on app restart.
+           * We simply can not rescue this situation, emit "error"
+           * event, with the hope that the application exits.
+           */
+          /* eslint-disable no-console */
+          const bugUrl = 'https://github.com/yagop/node-telegram-bot-api/issues/36#issuecomment-268532067';
+          console.error('error: Internal handling of The Offset Infinite Loop failed');
+          console.error(`error: Due to error '${requestErr}'`);
+          console.error('error: You may receive already-processed updates on app restart');
+          console.error(`error: Please see ${bugUrl} for more information`);
+          /* eslint-enable no-console */
+          return this.bot.emit('error', new errors.FatalError(err));
+        });
       })
       .finally(() => {
         if (this._abort) {