Too many connections Nodejs + mysql2/promise

Question

I am working in a proyect with nodejs + mysql2 and some times I got the error Too many connections.

My connection:

import {createPool, Pool} from 'mysql2/promise';

export async function connect(): Promise < any > {
  const connection: Pool = await createPool({
    host: 'localhost',
    port: 3306,
    user: 'root',
    password: '',
    database: 'mendozarq',
    connectionLimit: 10
  });
  return connection;
}

Controller:

import { Response, Request } from 'express';
import { FieldPacket, Pool } from 'mysql2/promise';

import { connect } from './../../classes/database';
import { Personal } from './../../models/personal.interface';

export const getAllPersonal = async (req: Request, res: Response) => {
    try {
        const conn: Pool = await connect();

        const [personal]: [any[], FieldPacket[]] = await conn.query('SELECT * FROM personal ORDER BY creadoEn DESC');
        conn.end();

        return res.status(200).json(personal);

    } catch (error) {
        return res.status(400).json({
            error
        });
    }
}

So, my question is I have to use createConnection instead of createPool or I just have to create one instance of my conn.

Answer 1

You should only be calling createPool once, then select from the pool every time thereafter.

So, it should look something like this. Create a constant that stores the pool. Then in the function if the pool already exists return the pool without calling createPool. If it doesn't exist, then you would call createPool and return the already created pool.

import {createPool, Pool} from 'mysql2/promise';

const globalPool: Pool | undefined = undefined;

export async function connect(): Promise <Pool> {

  // If the pool was already created, return it instead of creating a new one.
  if(typeof globalPool !== 'undefined') {
    return globalPool;
  }

  // If we have gotten this far, the pool doesn't exist, so lets create one.
  globalPool = await createPool({
    host: 'localhost',
    port: 3306,
    user: 'root',
    password: '',
    database: 'mendozarq',
    connectionLimit: 10
  });
  return globalPool;
}