Node.js connection pool produces infinite loop on error

I recently upgraded my generic-pool package to version 3 that makes use of promises - a concept I probably don't understand enough. I have managed to get it working, despite some unexpected differences in operation.

The problem I have is when I start testing error conditions. I have purposely set the password wrong, and when testing, I get an infinite loop of "connection failed" errors - indicating something is triggering the create function despite the error. I assume I have either configured the pool incorrectly, or I am acquiring improperly.

Generic pool factory:

const poolFactory = {
  create: function() {
    return new Promise(function(resolve, reject) {
      var client = mysql.createConnection({
        host: config.host,
        user: config.user,
        password: config.pass,
      });
      client.connect(function(err) {
        if (err != null) {
          log.write('ERROR', "Connection Error: MySQL: " + err.message);
          reject(err);
        } else {
          log.write('INFO', "MySQL Connection created.");
          resolve(client);
        }
      });

    })
  },
  destroy: function(client) {
    return new Promise(function(resolve) {
      client.end(function(err) {
        if (err != null) {
          log.write('ERROR', "DB Error: MySQL: " + err.message);
        } else {
          log.write('INFO', "Database connection closed.");
          resolve();
        }
      });
    })
  }
}

const cp = genericPool.createPool(poolFactory);

Test query that triggers the connection error:

cp.acquire().then(
  function(client) {
    client.query('USE ' + config.db, function(err, results, fields) {
      if (err != null) {
        log.write('ERROR', "DB test error: MySQL: " + err.message);
      } else {
        log.write('INFO', "MySQL connection tested successfully.");
        cp.release(client)
      }
    });
  }).catch(function(err) {
  cp.release(client);
  log.write('ERROR', "Pool Error: " + err.message);
});

My error log fills up with a million lines of:

 Connection Error: MySQL: ER_ACCESS_DENIED_ERROR: Access denied for user 'user'@'localhost' (using password: YES)

I am expecting a single error because I am testing error conditions. What am I doing wrong to get the infinite loop? I thought the reject(err) was supposed to put the promise in a state where it would not answer any more queries?

Can anyone point me in the right direction?

As always - thank-you very much!

EDIT: Here is a complete script that illustrate the problem if anyone cares to see the problem first hand! The console fills up with "ERROR MySQL Connection Error: ER_ACCESS_DENIED_ERROR: Access denied for user 'devUser'@'localhost' (using password: YES)". Thanks again.

// Test App to show logging issue

var pool = require('generic-pool'),
  mysql = require('mysql')

var config = {
  port: 8880,
  host: 'localhost',
  user: 'devUser',
  pass: 'wrong-pass',
  db: 'node-app-db'
}

const poolConfig = {
  max: 3
};

const poolFactory = {
  create: function() {
    return new Promise(function(resolve, reject) {
      var client = mysql.createConnection({
        host: config.host,
        user: config.user,
        password: config.pass,
      });
      client.connect(function(err) {
        if (err != null) {
          console.log('ERROR', "MySQL Connection Error: " + err.message);
          reject(err);
        } else {
          console.log('USAGE', "MySQL Connection created. " + cp.size + " of " + config.poolSize + " connections to DB in use.");
          resolve(client);
        }
      });

    })
  },
  destroy: function(client) {
    return new Promise(function(resolve) {
      client.end(function(err) {
        if (err != null) {
          console.log('ERROR', "DB Error: MySQL: " + err.message);
        } else {
          console.log('USAGE', "Database connection closed. Pool contains ' + cp.size + ' more connections.");
          resolve();
        }
      });
    })
  }
}

const cp = pool.createPool(poolFactory, poolConfig);

cp.acquire().then(
  function(client) {
    client.query('USE ' + config.db, function(err, results, fields) {
      if (err != null) {
        console.log('ERROR', "DB test error: MySQL: " + err.message);
      } else {
        console.log('READY', "MySQL connection tested successfully. DataServer ready for connections.");
        cp.release(client)
      }
    });
  }).catch(function(err) {
  cp.release(client);
  console.log('ERROR', "Pool Error: " + err.message);
});