节点js和mysql模块连接握手错误

Question

I've been trying around getting this mess of libs in js working with, i've been using Codeigniter for years and now i came upfront with needing to use mysql in node, but it's very mess and tricky since the connections are being my main problem.

So i'm making an adapter to make basic operations and using promise or not, it still gives me this error after making the first query.

"Cannot enqueue Quit after invoking quit." 

Well usually we open con, query and close and by doing that or even not closing it throws always. So my doubt is, what am i doing wrong or what do i need to add?

const mysql  = require('mysql')

let con = mysql.createConnection({
    host: "XXXXX",
    user: "XXX",
    password: "XXX",
    database: "XXX"
});;

con.on('error', function(err) {
    console.log("[mysql error]",err);
});

con.on('close', (err) => {
    console.log("Mysql closed connection");
})

/**
 * Executes a simple query with a given sql command and notifies when is complete
 * 
 * @param {string} sql
 * @param {function} callback
 * 
 * @return {object|json}
 */
executeSimpleQuery = (sql, args) =>
{
    return new Promise( (resolve, reject) => {
        con.connect( (err) => {
            con.query( sql, args, (err, rows) => {
                if (err) return reject(err);
                resolve(rows);
            })
        })
    })
}

/**
 * Closes a connection
 */
close = () =>
{
    return new Promise( ( resolve, reject ) => {
        con.end( err => {
            if ( err )
                return reject( err );
            resolve();
        } );
    } );
}

/**
 * Executes a simple query with a given sql command and notifies when is complete
 * 
 * @param {string} sql
 * @param {function} callback
 * 
 * @return {object|json}
 */
executeSimpleQueryx = (sql, callback) => 
{
    if (con.state !== "authenticated")
    {
        con.connect( (err) => {
            if (err) console.log("mysql error - " + err);
            console.log("Connection was been established in a simple query");
            con.query(sql, (err,result) => {
                if (err) throw err;
                callback(result);

            })
        });
    }
}

And i'm calling the function like this

adapter.executeSimpleQuery(`SELECT id from Users WHERE email= "${email}" LIMIT 1`)
        .then( rows => {
            console.log("We got row data--");
            console.log( JSON.stringify( rows ))
            callback(rows[0].id !== "undefined" ? rows[0].id : null)
        })
        .then( rows => {
            console.log("Closing db con..")
            return adapter.close()
        }, err => {
            return adapter.close().then( () => {throw err})
        })
        .catch( err => {
            console.log("EX rasise" + err)
        })

Answer 1

return adapter.close().then( () => {throw err})

Even if it closed correctly you are throwing an error. Print some error message first in success to check if this is the cause.

Note: Better use pool connection on connect and release after each query. It will save overhead of creating and deleting connection and make queries work faster. CI in php internally manages that.