Fix MongoDB connection issues causing 76.31% error rate in nutrition service

pet-nutrition-service/server.js

@@ -5,47 +5,158 @@
 const logger = require('pino-http');
 const NutritionFact = require('./nutrition-fact')
 
-main().catch(err => console.log(err));
+main().catch(err => {
+  console.error('Failed to start server:', err);
+  process.exit(1);
+});
+
+async function connectWithRetry() {
+  const MONGO_URI = process.env.MONGO_URI || 'mongodb://127.0.0.1:27017/nutrition';
+  const maxRetries = 5;
+  let retries = 0;
+
+  while (retries < maxRetries) {
+    try {
+      await mongoose.connect(MONGO_URI, {
+        serverSelectionTimeoutMS: 5000,
+        socketTimeoutMS: 45000,
+        maxPoolSize: 10,
+        minPoolSize: 2,
+        bufferCommands: false,
+        bufferMaxEntries: 0
+      });
+      console.log('Connected to MongoDB successfully');
+      return;
+    } catch (error) {
+      retries++;
+      console.error(`MongoDB connection attempt ${retries} failed:`, error.message);
+      if (retries >= maxRetries) {
+        throw new Error(`Failed to connect to MongoDB after ${maxRetries} attempts`);
+      }
+      await new Promise(resolve => setTimeout(resolve, Math.pow(2, retries) * 1000));
+    }
+  }
+}
 
 async function main () {
   const app = express();
 
-  // Middlware
+  // Middleware
   app.use(logger());
   app.use(express.json());
 
+  // Health check endpoint
+  app.get('/health', async (req, res) => {
+    try {
+      if (mongoose.connection.readyState === 1) {
+        await mongoose.connection.db.admin().ping();
+        res.status(200).json({ status: 'healthy', database: 'connected' });
+      } else {
+        res.status(503).json({ status: 'unhealthy', database: 'disconnected' });
+      }
+    } catch (error) {
+      res.status(503).json({ status: 'unhealthy', database: 'error', error: error.message });
+    }
+  });
+
   // GET: Find a NutritionFact by pet_type
   app.get('/nutrition/:pet_type', async (req, res) => {
     try {
       const { pet_type } = req.params;
-      const fact = await NutritionFact.findOne({ pet_type });
+
+      // Validate input
+      if (!pet_type || typeof pet_type !== 'string') {
+        return res.status(400).json({ message: 'Invalid pet_type parameter' });
+      }
+
+      // Check database connection
+      if (mongoose.connection.readyState !== 1) {
+        return res.status(503).json({ message: 'Database connection unavailable' });
+      }
+
+      const fact = await NutritionFact.findOne({ pet_type: pet_type.toLowerCase() }).lean();
+
       if (!fact) {
-        return res.status(404).json({ message: 'nutrition fact not found for the given pet_type' });
+        return res.status(404).json({ 
+          message: `Nutrition information not found for pet type: ${pet_type}`,
+          available_types: ['cat', 'dog', 'lizard', 'snake', 'bird', 'hamster']
+        });
       }
+
       res.status(200).json(fact);
     } catch (error) {
-      req.log.error(error);
-      res.status(500).json({ message: 'failed to fetch nutrition fact', error });
+      req.log.error({ error: error.message, stack: error.stack }, 'Error fetching nutrition fact');
+
+      if (error.name === 'MongooseError' || error.name === 'MongoError') {
+        res.status(503).json({ message: 'Database service temporarily unavailable' });
+      } else {
+        res.status(500).json({ message: 'Internal server error' });
+      }
     }
   });
 
   // GET: Fetch all NutritionFacts
   app.get('/nutrition', async (req, res) => {
     try {
-      const facts = await NutritionFact.find();
+      // Check database connection
+      if (mongoose.connection.readyState !== 1) {
+        return res.status(503).json({ message: 'Database connection unavailable' });
+      }
+
+      const facts = await NutritionFact.find().lean();
       res.status(200).json(facts);
     } catch (error) {
-      res.status(500).json({ message: 'Failed to fetch nutrition facts', error });
+      req.log.error({ error: error.message, stack: error.stack }, 'Error fetching all nutrition facts');
+
+      if (error.name === 'MongooseError' || error.name === 'MongoError') {
+        res.status(503).json({ message: 'Database service temporarily unavailable' });
+      } else {
+        res.status(500).json({ message: 'Internal server error' });
+      }
     }
   });
 
-  const MONGO_URI = process.env.MONGO_URI || 'mongodb://127.0.0.1:27017/'
-  await mongoose.connect(MONGO_URI);
+  // Connect to MongoDB with retry logic
+  await connectWithRetry();
+
+  // Handle MongoDB connection events
+  mongoose.connection.on('error', (err) => {
+    console.error('MongoDB connection error:', err);
+  });
+
+  mongoose.connection.on('disconnected', () => {
+    console.warn('MongoDB disconnected. Attempting to reconnect...');
+  });
+
+  mongoose.connection.on('reconnected', () => {
+    console.log('MongoDB reconnected');
+  });
 
   const PORT = process.env.PORT || 3000;
-  app.listen(PORT, () => {
+  const server = 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}`);
+  });
+
+  // Graceful shutdown
+  process.on('SIGTERM', async () => {
+    console.log('SIGTERM received, shutting down gracefully');
+    server.close(() => {
+      mongoose.connection.close(false, () => {
+        console.log('MongoDB connection closed');
+        process.exit(0);
+      });
+    });
+  });
+
+  process.on('SIGINT', async () => {
+    console.log('SIGINT received, shutting down gracefully');
+    server.close(() => {
+      mongoose.connection.close(false, () => {
+        console.log('MongoDB connection closed');
+        process.exit(0);
+      });
+    });
   });
 }