conn.js

const mysql = require('mysql');
const db_config = {
  host: process.env.DB_HOST,
  user: process.env.DB_USER,
  password: process.env.DB_PASS,
  database: process.env.DB_NAME
};

var con = mysql.createPool(db_config);

// Attempt to catch disconnects 
con.on('connection', function (connection) {
  console.log('DB Connection established');

  connection.on('error', function (err) {
    console.error(new Date(), 'MySQL error', err.code);
  });
  connection.on('close', function (err) {
    console.error(new Date(), 'MySQL close', err);
  });

});

module.exports = con;
// function handleDisconnect() {
//   console.log("\n New connection tentative...");
//   con = mysql.createConnection(db_config);
//   //- Destroy the current connection variable
//   //- Try to reconnect
//   con.connect(function (err){
//     if(err) {
//       console.log('error when connecting to db:', err);
//       setTimeout(handleDisconnect(), 2000);
//     }
//     else {
//       console.log("\n\t *** New connection established with the database. ***")
//     }
//   });

//   con.on('error', function(err) {
//     console.log('db error', err);
//     if(err.code === 'PROTOCOL_CONNECTION_LOST') { 
//       handleDisconnect(con);
//     } else if(err.code === "PROTOCOL_ENQUEUE_AFTER_QUIT"){
//         console.log("/!\\ Cannot establish a connection with the database. /!\\ ("+err.code+")");
//         handleDisconnect(con);
//     }
  
//     //- Fatal error : connection variable must be recreated
//     else if(err.code === "PROTOCOL_ENQUEUE_AFTER_FATAL_ERROR"){
//         console.log("/!\\ Cannot establish a connection with the database. /!\\ ("+err.code+")");
//         handleDisconnect();
//     }
  
//     //- Error because a connection is already being established
//     else if(err.code === "PROTOCOL_ENQUEUE_HANDSHAKE_TWICE"){
//         console.log("/!\\ Cannot establish a connection with the database. /!\\ ("+err.code+")");
//     }
  
//     //- Anything else
//     else{
//         console.log("/!\\ Cannot establish a connection with the database. /!\\ ("+err.code+")");
//         handleDisconnect();
//     }
//   });
// }

// handleDisconnect();

// module.exports = con;