Fix MongoDB connection and error handling in nutrition service

pet-nutrition-service/server.js

@@ -5,47 +5,142 @@
 const logger = require('pino-http');
 const NutritionFact = require('./nutrition-fact')
 
-main().catch(err => console.log(err));
+let isConnected = false;
 
-async function main () {
+// MongoDB connection with retry logic
+async function connectWithRetry() {
+  const maxRetries = 5;
+  const retryDelay = 1000; // Start with 1 second
+
+  for (let attempt = 1; attempt <= maxRetries; attempt++) {
+    try {
+      const MONGO_URI = process.env.MONGO_URI || 'mongodb://127.0.0.1:27017/nutrition';
+      await mongoose.connect(MONGO_URI, {
+        maxPoolSize: 10,
+        serverSelectionTimeoutMS: 5000,
+        socketTimeoutMS: 45000,
+      });
+      isConnected = true;
+      console.log('MongoDB connected successfully');
+      return;
+    } catch (error) {
+      console.error(`MongoDB connection attempt ${attempt} failed:`, error.message);
+      if (attempt === maxRetries) {
+        throw error;
+      }
+      // Exponential backoff
+      await new Promise(resolve => setTimeout(resolve, retryDelay * Math.pow(2, attempt - 1)));
+    }
+  }
+}
+
+main().catch(err => {
+  console.error('Application startup failed:', err);
+  process.exit(1);
+});
+
+async function main() {
   const app = express();
 
-  // Middlware
+  // Middleware
   app.use(logger());
   app.use(express.json());
 
+  // Health check endpoint
+  app.get('/health', (req, res) => {
+    const status = isConnected ? 'healthy' : 'unhealthy';
+    const statusCode = isConnected ? 200 : 503;
+    res.status(statusCode).json({
+      status,
+      database: isConnected ? 'connected' : 'disconnected',
+      timestamp: new Date().toISOString()
+    });
+  });
+
   // GET: Find a NutritionFact by pet_type
   app.get('/nutrition/:pet_type', async (req, res) => {
     try {
+      if (!isConnected) {
+        return res.status(503).json({ 
+          message: 'Database connection unavailable',
+          error: 'SERVICE_UNAVAILABLE'
+        });
+      }
+
       const { pet_type } = req.params;
-      const fact = await NutritionFact.findOne({ pet_type });
+
+      // Input validation
+      if (!pet_type || pet_type.trim() === '') {
+        return res.status(400).json({ 
+          message: 'Pet type is required',
+          error: 'INVALID_INPUT'
+        });
+      }
+
+      const fact = await NutritionFact.findOne({ pet_type: pet_type.toLowerCase() });
       if (!fact) {
-        return res.status(404).json({ message: 'nutrition fact not found for the given pet_type' });
+        return res.status(404).json({ 
+          message: `No nutrition information found for pet type: ${pet_type}`,
+          error: 'NOT_FOUND',
+          pet_type
+        });
       }
       res.status(200).json(fact);
     } catch (error) {
       req.log.error(error);
-      res.status(500).json({ message: 'failed to fetch nutrition fact', error });
+      res.status(500).json({ 
+        message: 'Failed to fetch nutrition information',
+        error: 'DATABASE_ERROR',
+        details: error.message
+      });
     }
   });
 
   // GET: Fetch all NutritionFacts
   app.get('/nutrition', async (req, res) => {
     try {
+      if (!isConnected) {
+        return res.status(503).json({ 
+          message: 'Database connection unavailable',
+          error: 'SERVICE_UNAVAILABLE'
+        });
+      }
+
       const facts = await NutritionFact.find();
       res.status(200).json(facts);
     } catch (error) {
-      res.status(500).json({ message: 'Failed to fetch nutrition facts', error });
+      req.log.error(error);
+      res.status(500).json({ 
+        message: 'Failed to fetch nutrition facts',
+        error: 'DATABASE_ERROR',
+        details: error.message
+      });
     }
   });
 
-  const MONGO_URI = process.env.MONGO_URI || 'mongodb://127.0.0.1:27017/'
-  await mongoose.connect(MONGO_URI);
+  // MongoDB connection monitoring
+  mongoose.connection.on('connected', () => {
+    isConnected = true;
+    console.log('MongoDB connection established');
+  });
+
+  mongoose.connection.on('error', (err) => {
+    isConnected = false;
+    console.error('MongoDB connection error:', err);
+  });
+
+  mongoose.connection.on('disconnected', () => {
+    isConnected = false;
+    console.log('MongoDB disconnected');
+  });
+
+  // Connect to MongoDB with retry logic
+  await connectWithRetry();
 
   const PORT = process.env.PORT || 3000;
   app.listen(PORT, () => {
     require('./eureka-client')('nutrition-service', PORT);
     require('./db-seed')();
-    console.log(`server running on port ${PORT}`);
+    console.log(`Server running on port ${PORT}`);
   });
 }