Why does the order of my gets change how the program works?

Question

I encountered a weird bug when doing a quick coding assignment.

Here is my code. Lets call this 'A'

//Grab all the animals from the database
WebApp.get('/all',(req,res) =>
    {
        const connection = mysql.createConnection({
            host : 'localhost',
            user : 'root',
            password : '1234', //Enter your password here 
            // I found that mySQL 8.0 uses a new default authent plugin whereas 5.7 uses a different one, If you get a ER_NOT_SUPPORTED_AUTH_MODE error from the response, try referring to this post to alter your root password. (https://stackoverflow.com/questions/50373427/node-js-cant-authenticate-to-mysql-8-0)
            database: 'animals'
        });

        const query = "SELECT * FROM animals";
        connection.query(query, (err, rows, fields) => 
        {
            if (err) 
            {
                console.error('error : ' + err.stack);
                res.sendStatus(500);
                return;
            }
            console.log("Fetched animals successfully");
            //console.log(rows); // Use this for error checking to see if a authent problem occurs.
            res.json(rows);
        });
    });

and this 'B'

//Grab a selected animal from the database given a valid Id.
WebApp.get('/:id',(req,res) =>
    {
        console.log("Fetching user with id: " + req.params.id);

        const connection = mysql.createConnection({
            host : 'localhost',
            user : 'root',
            password : '1234', //Enter your password here 
            // I found that mySQL 8.0 uses a new default authent plugin whereas 5.7 uses a different one, If you get a ER_NOT_SUPPORTED_AUTH_MODE error from the response, try referring to this post to alter your root password. (https://stackoverflow.com/questions/50373427/node-js-cant-authenticate-to-mysql-8-0)
            database: 'animals'
        });

        const animalId = req.params.id;
        const query = "SELECT * FROM animals WHERE id = ?";
        connection.query(query, [animalId], (err, rows, fields) => 
        {
            if (err) 
            {
                console.error('error : ' + err.stack);
                res.sendStatus(500);
                return;
            }
            console.log("Fetched animals successfully");
            //console.log(rows); // Use this for error checking to see if a authent problem occurs.
            res.json(rows);
        });
    });

For some reason, if I put A before B it works, and I get successful results from my queries. However, if I put B before A, B will return successfully, but A will return '[]'. Anyone know why?

Thanks for any help!

score 0 · Answer 1 · answered Apr 22 '20 at 23:59

Have you tried terminating the connection after each request, or considered using a connection pool? I am not familiar with nodeJS integration with MySQL, but in SQLServer, it is best to use ConnectionPool, when asynchronously making database requests.

Why does the order of my gets change how the program works?

1 Answers1