Improve error handling for menu data fetching and update HTML structure: Enhance error logging in menuDataController, provide user-friendly error messages, and streamline the index.html file by adding new script references while removing an unused image.

utils/withDbRetries.js

@@ -0,0 +1,51 @@
+const sequelize = require('../config/database');
+
+const DEFAULTS = {
+  attempts: 3,
+  baseDelayMs: 200,
+};
+
+function delay(ms) {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+/**
+ * Führt eine DB-Operation bis zu `attempts` mal aus. Nach einem Fehler:
+ * kurzes Backoff, dann Verbindung mit authenticate() neu prüfen (frische
+ * Verbindung aus dem Pool), erneuter Versuch.
+ * Kein sequelize.close() — würde die gemeinsame Instanz für alle Requests killen.
+ */
+async function withDbRetries(operation, options = {}) {
+  const { attempts, baseDelayMs } = { ...DEFAULTS, ...options };
+  let lastError;
+
+  for (let attempt = 1; attempt <= attempts; attempt++) {
+    try {
+      if (attempt > 1) {
+        const backoff = baseDelayMs * 2 ** (attempt - 2);
+        await delay(backoff);
+        try {
+          await sequelize.authenticate();
+        } catch (authErr) {
+          console.warn(
+            `DB authenticate vor Wiederholung ${attempt}/${attempts} fehlgeschlagen:`,
+            authErr.message
+          );
+        }
+      }
+      return await operation();
+    } catch (error) {
+      lastError = error;
+      console.error(
+        `DB-Operation Versuch ${attempt}/${attempts} fehlgeschlagen:`,
+        error.message
+      );
+      if (attempt === attempts) {
+        throw error;
+      }
+    }
+  }
+  throw lastError;
+}
+
+module.exports = { withDbRetries };