nodejs mysql connection pool

const mysql = require('mysql');

const pool = mysql.createPool({
  connectionLimit: 10,
  host: 'localhost',
  user: 'yourusername',
  password: 'yourpassword',
  database: 'yourdatabase'
});

pool.getConnection((err, connection) => {
  if (err) {
    if (err.code === 'PROTOCOL_CONNECTION_LOST') {
      console.error('Database connection was closed.');
    }
    if (err.code === 'ER_CON_COUNT_ERROR') {
      console.error('Database has too many connections.');
    }
    if (err.code === 'ECONNREFUSED') {
      console.error('Database connection was refused.');
    }
  }
  if (connection) {
    connection.release();
  }
  return;
});

module.exports = pool;

Explanation:

1. Require the 'mysql' module: Import the 'mysql' package to enable interaction with MySQL databases.

2. Create a Connection Pool: The createPool() method is used to create a pool of connections to the MySQL database. Parameters such as connectionLimit, host, user, password, and database are provided to configure the pool settings and connect to the specific database.

3. Handle Pool Connections:pool.getConnection() is used to retrieve a connection from the pool. It takes a callback function with parameters err (error) and connection. Inside the callback, error handling is performed. If there's an error, different error codes such as 'PROTOCOL_CONNECTION_LOST', 'ER_CON_COUNT_ERROR', or 'ECONNREFUSED' are checked and respective error messages are logged. If there's a connection, it's released back to the pool to be reused.

4. Export the Pool: The module.exports statement is used to export the created pool, making it available for use in other files/modules within the Node.js application.