Cannot enqueue Handshake after invoking quit

Question

I have implemented the following code:

module.exports = {
    getDataFromUserGps: function(callback)
    {
        connection.connect();
        connection.qu         


        

Answer 1

I think this issue is similar to mine:

1. Connect to MySQL
2. End MySQL service (should not quit node script)
3. Start MySQL service, Node reconnects to MySQL
4. Query the DB -> FAIL (Cannot enqueue Query after fatal error.)

I solved this issue by recreating a new connection with the use of promises (q).

mysql-con.js

'use strict';
var config          = require('./../config.js');
var colors          = require('colors');
var mysql           = require('mysql');
var q               = require('q');
var MySQLConnection = {};

MySQLConnection.connect = function(){
    var d = q.defer();
    MySQLConnection.connection = mysql.createConnection({
        host                : 'localhost',
        user                : 'root',
        password            : 'password',
        database            : 'database'
    });

    MySQLConnection.connection.connect(function (err) {
        if(err) {
            console.log('Not connected '.red, err.toString().red, ' RETRYING...'.blue);
            d.reject();
        } else {
            console.log('Connected to Mysql. Exporting..'.blue);
            d.resolve(MySQLConnection.connection);
        }
    });
    return d.promise;
};

module.exports = MySQLConnection;

mysqlAPI.js

var colors          = require('colors');
var mysqlCon        = require('./mysql-con.js');
mysqlCon.connect().then(function(con){
   console.log('connected!');
    mysql = con;
    mysql.on('error', function (err, result) {
        console.log('error occurred. Reconneting...'.purple);
        mysqlAPI.reconnect();
    });
    mysql.query('SELECT 1 + 1 AS solution', function (err, results) {
            if(err) console.log('err',err);
            console.log('Works bro ',results);
    });
});

mysqlAPI.reconnect = function(){
    mysqlCon.connect().then(function(con){
      console.log("connected. getting new reference");
        mysql = con;
        mysql.on('error', function (err, result) {
            mysqlAPI.reconnect();
        });
    }, function (error) {
      console.log("try again");
        setTimeout(mysqlAPI.reconnect, 2000);
    });
};

I hope this helps.

Answer 2

SOLUTION: to prevent this error(for AWS LAMBDA):

In order to exit of "Nodejs event Loop" you must end the connection, and then reconnect. Add the next code to invoke the callback:

connection.end( function(err) {
        if (err) {console.log("Error ending the connection:",err);}

       //  reconnect in order to prevent the"Cannot enqueue Handshake after invoking quit"

         connection = mysql.createConnection({
                host     : 'rds.host',
                port     :  3306,
                user     : 'user',
               password : 'password',
               database : 'target database'

               });
        callback(null, {
            statusCode: 200,
            body: response,

        });
    });

Answer 3

According to:

• Fixing Node Mysql "Error: Cannot enqueue Handshake after invoking quit.":

  http://codetheory.in/fixing-node-mysql-error-cannot-enqueue-handshake-after-invoking-quit/

TL;DR You need to establish a new connection by calling the createConnection method after every disconnection.

and

Note: If you're serving web requests, then you shouldn't be ending connections on every request. Just create a connection on server startup and use the connection/client object to query all the time. You can listen on the error event to handle server disconnection and for reconnecting purposes. Full code here.

---

From:

• Readme.md - Server disconnects:

  https://github.com/felixge/node-mysql#server-disconnects

It says:

Server disconnects

You may lose the connection to a MySQL server due to network problems, the server timing you out, or the server crashing. All of these events are considered fatal errors, and will have the err.code = 'PROTOCOL_CONNECTION_LOST'. See the Error Handling section for more information.

The best way to handle such unexpected disconnects is shown below:

function handleDisconnect(connection) {
  connection.on('error', function(err) {
    if (!err.fatal) {
      return;
    }

    if (err.code !== 'PROTOCOL_CONNECTION_LOST') {
      throw err;
    }

    console.log('Re-connecting lost connection: ' + err.stack);

    connection = mysql.createConnection(connection.config);
    handleDisconnect(connection);
    connection.connect();
  });
}

handleDisconnect(connection);

As you can see in the example above, re-connecting a connection is done by establishing a new connection. Once terminated, an existing connection object cannot be re-connected by design.

With Pool, disconnected connections will be removed from the pool freeing up space for a new connection to be created on the next getConnection call.

---

I have tweaked the function such that every time a connection is needed, an initializer function adds the handlers automatically:

function initializeConnection(config) {
    function addDisconnectHandler(connection) {
        connection.on("error", function (error) {
            if (error instanceof Error) {
                if (error.code === "PROTOCOL_CONNECTION_LOST") {
                    console.error(error.stack);
                    console.log("Lost connection. Reconnecting...");

                    initializeConnection(connection.config);
                } else if (error.fatal) {
                    throw error;
                }
            }
        });
    }

    var connection = mysql.createConnection(config);

    // Add handlers.
    addDisconnectHandler(connection);

    connection.connect();
    return connection;
}

Initializing a connection:

var connection = initializeConnection({
    host: "localhost",
    user: "user",
    password: "password"
});

Minor suggestion: This may not apply to everyone but I did run into a minor issue relating to scope. If the OP feels this edit was unnecessary then he/she can choose to remove it. For me, I had to change a line in initializeConnection, which was var connection = mysql.createConnection(config); to simply just

connection = mysql.createConnection(config);

The reason being that if connection is a global variable in your program, then the issue before was that you were making a new connection variable when handling an error signal. But in my nodejs code, I kept using the same global connection variable to run queries on, so the new connection would be lost in the local scope of the initalizeConnection method. But in the modification, it ensures that the global connection variable is reset This may be relevant if you're experiencing an issue known as

Cannot enqueue Query after fatal error

after trying to perform a query after losing connection and then successfully reconnecting. This may have been a typo by the OP, but I just wanted to clarify.

Answer 4

inplace of connection.connect(); use -

if(!connection._connectCalled ) 
{
connection.connect();
}

if it is already called then connection._connectCalled =true,
& it will not execute connection.connect();

note - don't use connection.end();

Answer 5

Do not connect() and end() inside the function. This will cause problems on repeated calls to the function. Make the connection only

var connection = mysql.createConnection({
      host: 'localhost',
      user: 'node',
      password: 'node',
      database: 'node_project'
    })

connection.connect(function(err) {
    if (err) throw err

});

once and reuse that connection.

Inside the function

function insertData(name,id) {

  connection.query('INSERT INTO members (name, id) VALUES (?, ?)', [name,id], function(err,result) {
      if(err) throw err
  });


}

Answer 6

You can use debug: false,

Example: //mysql connection

var dbcon1 = mysql.createConnection({
      host: "localhost",
      user: "root",
      password: "",
      database: "node5",
      debug: false,
    });