added retry logic on DB after fail

.gitignore

@@ -0,0 +1 @@
+mysql-db

backend/Dockerfile

@@ -1,20 +1,15 @@
-# Use the official Node.js 20 image as the base image
-FROM node:20
+FROM node 
 
-# Set the working directory in the container
 WORKDIR /app
 
-# Copy the package.json and package-lock.json files to the container
 COPY package*.json ./
 
-# Install the dependencies
 RUN npm install
 
-# Copy the rest of the application's source code to the container
 COPY . .
 
-# Expose the port that the application listens on
 EXPOSE 3000
 
-# Start the Node.js application
-CMD [ "npm", "start" ]
+CMD ["npm", "start"]
+
+

backend/server.js

@@ -1,99 +1,91 @@
 const express = require("express");
 const mysql = require("mysql2");
-var cors = require("cors");
+const cors = require("cors");
 const bodyParser = require("body-parser");
 
-// Create the Express app
 const app = express();
 app.use(cors());
 app.use(bodyParser.json());
 
-// Create a connection to the MySQL database
+// MySQL connection config
 const mysqlConfig = {
-  host: process.env.DB_HOST || "db",
+  host: process.env.DB_HOST || "mysql",
   port: process.env.DB_PORT || "3306",
   user: process.env.DB_USER || "root",
   password: process.env.DB_PASSWORD || "pass123",
   database: process.env.DB_NAME || "appdb",
 };
 
-let con = null;
-const databaseInit = () => {
+let con;
+
+// Try connecting with retry logic (useful when DB takes time to start)
+const connectWithRetry = (attempt = 1) => {
+  console.log(`Attempting to connect to DB... (try ${attempt})`);
   con = mysql.createConnection(mysqlConfig);
+
   con.connect((err) => {
     if (err) {
-      console.error("Error connecting to the database: ", err);
-      return;
+      console.error("❌ DB connection failed:", err.message);
+      // Try again after 3 seconds
+      setTimeout(() => connectWithRetry(attempt + 1), 3000);
+    } else {
+      console.log("✅ Connected to MySQL database");
+      initDatabase(); // Create DB and table if missing
     }
-    console.log("Connected to the database");
   });
 };
 
-const createDatabase = () => {
-  con.query("CREATE DATABASE IF NOT EXISTS appdb", (err, results) => {
-    if (err) {
-      console.error(err);
-      return;
-    }
-    console.log("Database created successfully");
-  });
-};
+// Initialize DB and table
+const initDatabase = () => {
+  con.query("CREATE DATABASE IF NOT EXISTS appdb", (err) => {
+    if (err) return console.error("Error creating DB:", err.message);
+    console.log("✅ Database ensured");
 
-const createTable = () => {
-  con.query(
-    "CREATE TABLE IF NOT EXISTS apptb (id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(255))",
-    (err, results) => {
-      if (err) {
-        console.error(err);
-        return;
-      }
-      console.log("Table created successfully");
-    }
-  );
+    // Switch to database
+    con.changeUser({ database: "appdb" }, (err) => {
+      if (err) return console.error("Error switching DB:", err.message);
+
+      con.query(
+        `CREATE TABLE IF NOT EXISTS apptb (
+          id INT AUTO_INCREMENT PRIMARY KEY,
+          name VARCHAR(255)
+        )`,
+        (err) => {
+          if (err) console.error("Error creating table:", err.message);
+          else console.log("✅ Table ensured");
+        }
+      );
+    });
+  });
 };
 
-// GET request
+// Routes
 app.get("/user", (req, res) => {
-  databaseInit();
   con.query("SELECT * FROM apptb", (err, results) => {
     if (err) {
-      console.error(err);
+      console.error("Error fetching data:", err);
       res.status(500).send("Error retrieving data from database");
     } else {
       res.json(results);
     }
   });
 });
 
-// POST request
 app.post("/user", (req, res) => {
-  con.query(
-    "INSERT INTO apptb (name) VALUES (?)",
-    [req.body.data],
-    (err, results) => {
-      if (err) {
-        console.error(err);
-        res.status(500).send("Error retrieving data from database");
-      } else {
-        res.json(results);
-      }
+  const { data } = req.body;
+  con.query("INSERT INTO apptb (name) VALUES (?)", [data], (err, results) => {
+    if (err) {
+      console.error("Error inserting data:", err);
+      res.status(500).send("Error inserting data");
+    } else {
+      res.json(results);
     }
-  );
-});
-
-app.post("/dbinit", (req, res) => {
-  databaseInit();
-  createDatabase();
-  res.json("Database created successfully");
-});
-
-app.post("/tbinit", (req, res) => {
-  databaseInit();
-  createTable();
-  res.json("Table created successfully");
+  });
 });
 
-// Start the server
+// Start server
 app.listen(3000, () => {
-  console.log("Server running on port 3000");
+  console.log("🚀 Server running on port 3000");
+  connectWithRetry(); // Start DB connection with retry logic
 });
+

docker-compose.yml

@@ -1,41 +1,47 @@
 version: "3.8"
 
 services:
-  db: # Defines the 'db' service for MySQL database
-    image: mysql:8.0 # Uses the MySQL 8.0 Docker image
-    environment: # Sets environment variables for the database configuration
-      - MYSQL_DATABASE=appdb # Specifies the name of the database
-      - MYSQL_PASSWORD=pass123 # Sets the password for the MySQL user
-      - MYSQL_ROOT_PASSWORD=pass123 # Sets the root password for MySQL
+  mysql:
+    restart: always
+    image: mysql
+    environment:
+      - MYSQL_DATABASE=appdb
+      - MYSQL_PASSWORD=pass123
+      - MYSQL_ROOT_PASSWORD=pass123
     networks:
-      - sameNetworkAsMysql # Connects the service to the 'sameNetworkAsMysql' network
-    ports:
-      - 3307:3306 # Maps the container's port 3306 to the host's port 3307
+      - project-net
     volumes:
-      - ./script.sql:/docker-entrypoint-initdb.d/script.sql
+      - ./mysql-db:/var/lib/mysql
+    healthcheck:
+      test: ["CMD-SHELL", "mysqladmin ping -h localhost -uroot -ppass123 || exit 1"]
+      interval: 10s
+      retries: 5
+      start_period: 30s
 
-  api: # Defines the 'api' service for the backend API
-    build: # Builds the backend API using the provided Dockerfile
-      context: ./backend # Specifies the build context directory for the backend
-      dockerfile: Dockerfile # Specifies the Dockerfile to use for building the backend
+  backend:
+    build:
+      context: ./backend
     ports:
-      - 3000:3000 # Maps the container's port 3000 to the host's port 3000
+      - "3000:3000"
     networks:
-      - sameNetworkAsMysql # Connects the service to the 'sameNetworkAsMysql' network
+      - project-net
     depends_on:
-      - db # Specifies that the 'api' service depends on the 'db' service
+      mysql:
+        condition: service_healthy   
 
-  frontend: # Defines the 'frontend' service for the frontend app
-    restart: on-failure # Restarts the container if it fails
-    build: # Builds the frontend app using the provided Dockerfile
-      context: ./frontend # Specifies the build context directory for the frontend
+  frontend:
+    restart: on-failure
+    build:
+      context: ./frontend
     ports:
-      - 3001:3000 # Maps the container's port 3000 to the host's port 3001
+      - "3001:3000"
     networks:
-      - sameNetworkAsMysql # Connects the service to the 'sameNetworkAsMysql' network
+      - project-net
     depends_on:
-      - api # Specifies that the 'frontend' service depends on the 'api' service
+      - backend
+
 
 networks:
-  sameNetworkAsMysql: # Defines the 'sameNetworkAsMysql' network
-    driver: bridge # Specifies the network driver as 'bridge'
+  project-net:
+volumes:
+  mysql-db:

frontend/Dockerfile

@@ -1,23 +1,15 @@
-# Use the official Node.js 20 image as the base image
-FROM node:20
+FROM node 
 
-# Set the working directory in the container
 WORKDIR /app
 
-# Copy the package.json and package-lock.json files to the container
 COPY package*.json ./
 
-# Install the dependencies
 RUN npm install
 
-# Copy the rest of the application's source code to the container
-COPY . .
+COPY . . 
 
-# Build the React.js application
 RUN npm run build
 
-# Expose the port that the application listens on
 EXPOSE 3001
 
-# Start a simple web server to serve the built React.js files
 CMD [ "npx", "serve", "-s", "build" ]