pool.end() kills connection.query() in promise mode

I am working on server that handles several requests asynchronously. Found the problem when close the app gracefully while mysql query is still running. To stop the app, I call pool.end() created by mysql.createPool({}).promise();. But looks like, pool.end() just closes the pool without checking that some connections from the pool are still running. Connection query throws the exception with Error: Pool is closed. Or I do something wrong or inappropriate. Any suggestions?

Exception is:

D:\server\node_modules\mysql2\lib\pool.js:57
          return cb(new Error('Pool is closed.'));
                    ^
Error: Pool is closed.
    at D:\server\node_modules\mysql2\lib\pool.js:57:21
    at PoolConnection.<anonymous> (D:\server\node_modules\mysql2\lib\connection.js:777:13)
    at Object.onceWrapper (node:events:628:26)
    at PoolConnection.emit (node:events:513:28)
    at ClientHandshake.<anonymous> (D:\server\node_modules\mysql2\lib\connection.js:121:14)
    at ClientHandshake.emit (node:events:513:28)
    at ClientHandshake.execute (D:\server\node_modules\mysql2\lib\commands\command.js:49:10)
    at PoolConnection.handlePacket (D:\server\node_modules\mysql2\lib\connection.js:456:32)
    at PacketParser.onPacket (D:\server\node_modules\mysql2\lib\connection.js:85:12)
    at PacketParser.executeStart (D:\server\node_modules\mysql2\lib\packet_parser.js:75:16)
Node.js v18.12.0
Process finished with exit code 1

Here is simple test to reproduce:

'use strict';
const mysql = require('mysql2');
let pool;
// ---------------------------------------------------------------------
const start = () => {
  pool = mysql.createPool({host: 'localhost', user: '', password: ''})
  .promise();
}
// ---------------------------------------------------------------------
const stop = () => {
  if (pool) {
    pool.end();
    pool = undefined;
  }
}
// ---------------------------------------------------------------------
const query = (sql, params) => {
  let connection;
  return pool
  .getConnection()
  .then((conn) => {
    connection = conn;
    return connection.query(sql, params);
  })
  .then(([rows, fields]) => {
    connection.release();
    console.log('Rows', rows, fields);
  })
  .catch((ex) => {
    throw ex;
  });
}
// ---------------------------------------------------------------------
// Run
start();
query('SELECT 1');
stop();

My code is bit more sophisticated. I can have several complex queries executing in the pool and some queries waiting in a pool queue. But the root of the problem is the same.

If I wrap stop() in setTimeout() with short delay:

...

setTimeout(() => {
  stop();
}, 100)

the test finishes normally with exit code 0.

I am using:

Product	Version
mysql2:	2.3.3
nodejs:	18.12.0
mysql:	8.0.31
OS:	Windows 10

[sergru]

I took the liberty to implement the workaround to my issue. Here is my changes in mysql2/promise.js, mysql2/lib/pool.js, and test script repro-exception.js . In this implementation there are no exceptions Error: Pool is closed anymore, and all asynchronous calls of query() and stop() executed as expected. The log of all calls added for debug purposes.

Files from mysql2:

• mysql2/promise.js
• mysql2/lib/pool.js

Test file:

• test/repro-exception.js

Kill .txt extra extension when download files. Somehow .js files are not allowed to be dropped in github.

Search for ADDED: to see all my changes in 2 mysql2 files.

[sergru]

I can make repro.js for this scenario if you like. But the simple test I sent first reproduce the exact problem.