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Last active December 9, 2022 10:24
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Promisified MySQL middleware for Node.js
const util = require('util')
const mysql = require('mysql')
const pool = mysql.createPool({
connectionLimit: 10,
host: 'localhost',
user: 'root',
password: 'password',
database: 'my_database'
// Ping database to check for common exception errors.
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()
// Promisify for Node.js async/await.
pool.query = util.promisify(pool.query)
module.exports = pool
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hoogw commented May 31, 2018

After I upgrade node -v to 9.6.1. I finally get it works.

  1. can you update your script by add:
    // node -v must > 8.x var util = require('util');

  2. you must use async function to be able to use await.


           var pool = require('./database')
       // node -v must > 8.x, --> async / await  
      router.get('/:template', async function(req, res, next) 
        try {
         var _sql_rest_url = 'SELECT * FROM arcgis_viewer.rest_url WHERE id='+ _url_id;
         var rows = await pool.query(_sql_rest_url)
             _url  = rows[0].rest_url // first record, property name is 'rest_url'
             if (_center_lat   == null) {_center_lat = rows[0].center_lat  }
             if (_center_long  == null) {_center_long= rows[0].center_long }
             if (_center_zoom  == null) {_center_zoom= rows[0].center_zoom }          
             _place = rows[0].place
     } catch(err) {
         throw new Error(err)


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hagemann commented Jun 7, 2018

Thanks for mentioning, @hoogw. The snippet has been amended on line 1.

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hoogw commented Jun 11, 2018

This is a very cool script, very easy and handy to use.

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birante commented Jul 9, 2018

Thanks a lot

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Thank you for this great script, it helped me in handling closed connections, and the promisify part helped keeping the code much cleaner than callback functions.

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ghost commented Sep 11, 2018


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scandar commented Nov 15, 2018

using pool.query after requiring in any other module throws this error
SyntaxError: await is only valid in async function

which i've handled by using an IIFE

(async function getbooks() {
  const res = await pool.query('SELECT * FROM books');

i don't know if this is the best way to handle this case :/

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kachar commented Dec 21, 2018

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me gustaría saber como realizar un servicio con este método de conexión para realizar un login

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kamalhm commented Mar 7, 2019

As usual... There's a lib for this


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rpf5573 commented Apr 26, 2019

pool.query = util.promisify(pool.query);

this code is not work on typescript.

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Thank you very very much. My Node.js MySQL application on heroku was frequently crashing. Looked all over for a fix and ended up finding your article on medium about using pool middleware. It worked perfectly and now my application does not crash anymore. Thanks again!!

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hagemann commented Jul 2, 2019

@umrgit123 Glad you found this middleware and that it solved your crashes! Thanks a lot for commenting, and I wish you lots of growth with your application.

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Otomakan commented Oct 30, 2019

For typescript you can do something like

import mysql, { Pool, QueryFunction } from 'mysql'
import { promisify } from 'util'

interface PromisifiedPool extends Omit<Pool, 'query'> {
    query: QueryFunction | Function;

const pool: PromisifiedPool = mysql.createPool({
    host: `${process.env.DB_HOST}`,
    user: `${process.env.DB_USER}`,
    password: `${process.env.DB_PASSWORD}`,
    database: `${process.env.DB_NAME}`

pool.query = promisify(pool.query)

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Thanks a lot. This is useful

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whenever i use await it shows 3 dot (...) below it meaning 'await' has no effect on the type of this expression.

i have used everything mentioned above

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zirtrex commented Nov 2, 2020

hi, how I add queryFormat to pool connections?

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Hi there,

I am using this database connection configuration but somehow it is throwing an error while fire the query.

import { pool } from '../../config/mysql-config';
public async insertRecords() {
  try {
    const SQL = `INSERT INTO ${tableName} (description, title)
      VALUES ("description", "title")`

    const result = await pool.query(SQL)
    return result
  } catch (error) {
    throw new Error(error);

Screenshot from 2021-05-24 11-29-29

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