I'm creating a promise based API. Everything works fine if I make one request at a time, but, if 2 or more requests hit the server within a second of each other, I get the following error
Error: Cannot enqueue Quit after invoking quit
The odd thing is, I get a valid and correct results returned to API requests, but, clearly something is wrong.
I've created a small project on gitHub. You can check it out, I've created an SQL seeder with 2 users so you can just copy paste the query into your database (the seeder even creates a new database)
The project is small, just put your database credentials in the the configs/mysql.js file, then run the file node multiple_sends.js
You'll see that the correct answer is returned, but node blows errors.
I don't think the error is in the mysql module. The reason is, if I take the code from my model and create a CLI script, no errors are returned, mysql doesn't issue any warnings
// models/user.js
let mysql = require('mysql');
let configs = {
host : '127.0.0.1',
user : 'root',
password : 'something',
database : 'demo'
}
/**
* This constructor function is responsible for running queries against
* the mysql database
*/
function Users()
{
// These are PRIVATE variables, they can only be accessed within this class
let mysql_connection = null;
this.getUserByEmail = function(email)
{
let parent = this;
mysql_connection = mysql.createConnection(configs);
return this.mysqlConnect()
.then((connectionId) =>
{
console.log(`getUserByEmail: connection id: ${connectionId}`);
let sql = 'SELECT user_id, first_name, last_name, upassword, email, '
+ 'birthday, roles FROM users WHERE email = ?';
return parent.runQuery(sql, [email]);
})
.then((results) =>
{
if (results.resultSet.length === 0) {
return null;
}
let resultSet = results.resultSet[0];
// return our result to the calling method.
return (resultSet);
})
.catch(error => {
throw error;
})
}
/**
* Run this method when trying to connect to the database
* @param Object error
* @return Promise
*/
this.mysqlConnect = function()
{
return new Promise(function(resolve, reject)
{
mysql_connection.connect(function(error)
{
if (error) {
console.log('Error making connection', error);
throw "Failed connection to database";
}
// we don't have to return anything, this is just to show that Promises
// can return
resolve(mysql_connection.threadId);
});
});
}
/**
* use this method for running selects
* @param string query - well formed query
* @return Promise
*/
this.runQuery = function(query, params)
{
return new Promise(function(resolve, reject)
{
mysql_connection.query(query, params, function(error, results, fields)
{
mysql_connection.end((err) => {
if (err) {
console.log('error terminating connection: ', mysql_connection.threadId);
console.log('error ', err);
}
});
if (error) {
reject(error);
}
resolve({resultSet: results, fieldSet: fields});
});
});
}
}
module.exports = Users;
Here is script which calls the model
//main.js
let Users = require ('./models/user');
function getUser1Info()
{
user1.getUserByEmail('original.logger@example.com')
.then(userData1 => {
let ctime = new Date();
console.log(ctime.getTime(), 'user data: ', userData1.user_id)
})
.catch((error) => {
console.log('error!', error);
});
}
function getUser2Info()
{
user2.getUserByEmail('billy.b.parker@example.com')
.then(userData2 => {
let ctime = new Date();
console.log(ctime.getTime(), 'user data: ', userData2.user_id)
})
.catch((error) => {
console.log('error!', error);
});
}
let user1 = new Users();
let user2 = new Users();
setTimeout(() => {
getUser1Info();
}, 1000);
setTimeout(() => {
getUser2Info();
}, 999);
This code un-modified from the models/user.js in my API. This leads me to believe that the way I'm creating models in Express is fundamentally broken.
Any help is appreciated
