added tester

backend/services/database.js

@@ -1,16 +1,42 @@
 import mysql from "mysql2";
 import dotenv from "dotenv";
+import dns from "dns/promises";
 dotenv.config();
 
+// Validate required envs early
+const required = ["DB_HOST", "DB_USER", "DB_PASSWORD", "DB_NAME"];
+for (const k of required) {
+  if (!process.env[k]) {
+    throw new Error(`Missing required env var: ${k}`);
+  }
+}
+
 const pool = mysql
   .createPool({
     host: process.env.DB_HOST,
     user: process.env.DB_USER,
     password: process.env.DB_PASSWORD,
     database: process.env.DB_NAME,
+    waitForConnections: true,
+    connectionLimit: 10,
+    queueLimit: 0,
   })
   .promise();
 
+// Optional: resolve host and test a connection at startup for clearer errors
+(async () => {
+  try {
+    await dns.lookup(process.env.DB_HOST);
+    const conn = await pool.getConnection();
+    conn.release();
+  } catch (e) {
+    console.error(
+      `Database connectivity check failed for host "${process.env.DB_HOST}":`,
+      e.code || e.message
+    );
+  }
+})();
+
 export const loginFunc = async (username, password) => {
   const [result] = await pool.query(
     "SELECT * FROM users WHERE username = ? AND password = ?",