Node js + Mysql : cannot enqueue because of fatal errors

Question

I'm running a application with node js (more specifically express js) and I save some datas with a mysql client.

It perfectly works for some time with no issue but then all of suddden I get these erros:

Trace: Cannot enqueue Quit after fatal error. at Protocol._validateEnqueue (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\protocol\Protocol.js:218:11) at Protocol._enqueue (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\protocol\Protocol.js:135:13) at Protocol.quit (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\protocol\Protocol.js:88:23) at PoolConnection.end (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\Connection.js:255:18) at Pool._purgeConnection (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\Pool.js:259:16) at PoolConnection._removeFromPool (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\PoolConnection.js:70:8) at PoolConnection. (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\PoolConnection.js:29:12) at emitOne (events.js:77:13) at PoolConnection.emit (events.js:169:7) at PoolConnection.Connection._handleProtocolError (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\Connection.js:439:8) Trace: Cannot enqueue Query after fatal error. at Protocol._validateEnqueue (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\protocol\Protocol.js:218:11) at Protocol._enqueue (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\protocol\Protocol.js:135:13) at PoolConnection.query (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\Connection.js:214:25) at Object.fetchDatas (C:\nodejs\twelve-coiffure\public\javascripts\twelvebase.js:94:12) at C:\nodejs\twelve-coiffure\routes\index.js:7:7 at Layer.handle [as handle_request] (C:\nodejs\twelve-coiffure\node_modules\express\lib\router\layer.js:95:5) at next (C:\nodejs\twelve-coiffure\node_modules\express\lib\router\route.js:131:13) at Route.dispatch (C:\nodejs\twelve-coiffure\node_modules\express\lib\router\route.js:112:3) at Layer.handle [as handle_request] (C:\nodejs\twelve-coiffure\node_modules\express\lib\router\layer.js:95:5) at C:\nodejs\twelve-coiffure\node_modules\express\lib\router\index.js:277:22 C:\nodejs\twelve-coiffure\public\javascripts\twelvebase.js:26 throw(message); ^

Error: Cannot enqueue Query after fatal error. at Protocol._validateEnqueue (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\protocol\Protocol.js:199:16) at Protocol._enqueue (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\protocol\Protocol.js:135:13) at PoolConnection.query (C:\nodejs\twelve-coiffure\node_modules\mysql\lib\Connection.js:214:25) at Object.fetchDatas (C:\nodejs\twelve-coiffure\public\javascripts\twelvebase.js:94:12) at C:\nodejs\twelve-coiffure\routes\index.js:7:7 at Layer.handle [as handle_request] (C:\nodejs\twelve-coiffure\node_modules\express\lib\router\layer.js:95:5) at next (C:\nodejs\twelve-coiffure\node_modules\express\lib\router\route.js:131:13) at Route.dispatch (C:\nodejs\twelve-coiffure\node_modules\express\lib\router\route.js:112:3) at Layer.handle [as handle_request] (C:\nodejs\twelve-coiffure\node_modules\express\lib\router\layer.js:95:5) at C:\nodejs\twelve-coiffure\node_modules\express\lib\router\index.js:277:22

The problem is that I really can't find where the issue comes from in my code, and I don't even know why sometimes in works and sometimes not.

Here is my code to start the database:

var mysql = require('mysql');
var dbPool = mysql.createPool({
 connectionLimit: 50,
 waitForConnections: true,
 queueLimit: 0,
 host: '*my host*',
 user: '*me*',
 password: '*my password*',
 database: '*heroku database*',
 wait_timeout:28800,
 connect_timeout:10,
 debug:true
});

dbPool.getConnection(function(err, connection) {
 if (err) throw (err);

 var db = connection;

 fetchDatas = function(callback) {

    // openDatabase();

    var servicesFemmes, servicesHommes, products;

    db.query("SELECT * FROM servicesFemmes", function(err, servicesFemmes, fields) {

        if (err) {
            callback(sendError(err));
        } else {

            db.query("SELECT * FROM servicesHommes", function(err, servicesHommes, fields) {
                if (err) {
                    callback(sendError(err));
                } else {
                    db.query("SELECT * FROM produits", function(err, products, fields) {
                        if (err) {
                            callback(sendError(err));
                        } else {
                            db.query("SELECT * FROM carousel", function(err, carousel, fields) {
                                if (err) {
                                    callback(sendError(err));
                                } else {
                                    callback(null, servicesFemmes, servicesHommes, products, carousel);
                                }
                            });
                        }
                    });
                }
            });
        }
    });
}
}
}

Of course I'm calling fetchDatas() from another file to get all the datas to display.

You probably want to use a promise library here like what Sequelize offers because this is already in "callback hell". — tadman
do you ever release the connection so that it can be reused again by the pool? + where does the db object come from? shouldn't that be the connection object instead? — Johannes Merz
ok @tadman I'm probably going to use that real soon if I don't find a solution here. I just wanted to keep simple (I had start with sqlite3 but it wasn't compatible with heroku hosting) since it's juste a simple page for a small shop. — Arthur Feldman
@Johannes Merz well I do release the connection for every other sql functions I use but with this one I have a message that says the connection is already released so I figured out it was already done somewhere else (can't find exactly where). And for the db object yes sorry I'm going to edit the post: I missed the line "var db = connection" — Arthur Feldman
@tadman I finally went with your advice and used Sequelize. That was perfect and solved my issues. Thank you — Arthur Feldman

Arthur Feldman Arthur Feldman · Accepted Answer · 2016-08-23T23:31:05

Finally, I gave up on plain MYSQL and started using Sequelize instead. Here is my code (which finally works):

var mysql = require('mysql');
var Sequelize = require('sequelize');

var sequelize = new Sequelize('database name', 'username', 'password', {
host: 'your host url',
dialect: 'mysql',

pool: {
    max: 10,
    min: 0,
    idle: 3000
}
});


//Models' creation
var servicesHommes = sequelize.define('servicesHommes', {
 nom: {
     type: Sequelize.STRING,
     field: 'nom'
 },
 cheveuxLongs: {
     type: Sequelize.STRING,
     field: 'cheveuxLongs'
 },
 cheveuxCourts: {
     type: Sequelize.STRING,
     field: 'cheveuxCourts'
 }
}, {
 freezeTableName: true
});

var servicesFemmes = sequelize.define('servicesFemmes', {
nom: {
    type: Sequelize.STRING,
    field: 'nom'
},
cheveuxLongs: {
    type: Sequelize.STRING,
    field: 'cheveuxLongs'
},
cheveuxCourts: {
    type: Sequelize.STRING,
    field: 'cheveuxCourts'
}
}, {
freezeTableName: true
});

var carousel = sequelize.define('carousel', {
 photo: {
     type: Sequelize.STRING,
     field: 'photo'
 }
});

var produits = sequelize.define('produits', {
  marque: {
     type: Sequelize.STRING,
     field: 'marque'
  },
  nom: {
    type: Sequelize.STRING,
    field: 'nom'
  },
  photo: {
    type: Sequelize.STRING,
    field: 'photo'
  }
}, {
freezeTableName: true
});

synchronizeBdd = function(callback) {

sequelize.sync().then(function() {
//any function querying the database should be placed here in this callback


    fetchDatas = function(callback) {

        servicesFemmes.findAll().then(function(femmes) {
            servicesHommes.findAll().then(function(hommes) {
                produits.findAll().then(function(products) {
                    carousel.findAll().then(function(carousels) {
                        callback(null, femmes, hommes, products, carousels);
                    })
                })
            })
        });
    }

    //end of sync()
    exports.fetchDatas = fetchDatas;
    callback();
});
}

exports.synchronize = synchronizeBdd;

Then I have another file calling my function "synchronize" exported on the last line of previous snippet ("exports.synchronize = synchronizeBdd"):

var bdd = require('fileWithSequelizeInstantiation')

bdd.synchronize(function() {
 //here I call the functions related to my database. In my case: bdd.fetchDatas()
})

Node js + Mysql : cannot enqueue because of fatal errors

2 Answers