Mysql Pool Failsafe Connection

pool-connection.ts

import * as mysql from "mysql";
import {MysqlError, Pool, PoolConnection} from "mysql";
import {dbMysqlConf} from "./config";

const MAX_ATTEMPS = 10;
let attempts = 0;

export const managePoolConnection = (app:any) => new Promise((resolve: (status:string) => void, reject: (status:string) => void) => {

    let pool: Pool = mysql.createPool(dbMysqlConf);

    pool.getConnection((err: MysqlError, connection: PoolConnection) => {
        if (err) {
            attempts++;
            if (attempts > MAX_ATTEMPS) {
                reject(`Mysql Error: More than ${MAX_ATTEMPS}, cancelling. Error ${err.errno} :  ${err.sqlMessage}`)
            } else {
                setTimeout(() => {
                    managePoolConnection(app).then(resolve, reject)
                }, 2000);
            }
            return;
        } else {
            attempts = 0;

            (app as any).poolConnection = connection;

            connection.on('error', (err: MysqlError) => {

                console.log(`Mysql Error: Cannot establish a connection with the database.  (${err.code})`);

                switch (err.code) {
                    case "PROTOCOL_CONNECTION_LOST":
                        managePoolConnection(app).then(resolve, reject);
                        break;
                    case "PROTOCOL_ENQUEUE_AFTER_QUIT":
                        managePoolConnection(app).then(resolve, reject);
                        break;
                    case "PROTOCOL_ENQUEUE_AFTER_FATAL_ERROR":
                        managePoolConnection(app).then(resolve, reject);
                        break;
                    case "PROTOCOL_ENQUEUE_HANDSHAKE_TWICE":
                        //managePoolConnection.then(resolve, reject);
                        break;
                    default:
                        managePoolConnection(app).then(resolve, reject);
                        break;
                }
            });

            resolve(`Mysql: connection successful`);
        }

    });

});

Then in the index.ts (app is the express server but could be something else)

managePoolConnection(app).then(
    status => console.log(status),
    err => console.log(err)
);