Node.js MySQL connection not connecting but no errors are shown

Question

I am new to Node and have been using it for just over a week now, everything's fine until I tried to connect to a MySQL database and I'm having no luck.

I have installed the necessary files;

npm install mysql

and my code is as follows;

const mySQL = require('mysql');

const mySQLCon = mySQL.createConnection({
    host: "localhost",
    user: "username",
    password: "password",
    database: "databaseName"
});

function connectTest() {
    mySQLCon.connect(function(err) {
        if(err){
            console.log(err.code);
            console.log(err.fatal);
        }
    });
    console.log(mySQLCon.state);
    sSQL = "SELECT sField FROM tblName WHERE iID = 1";
    mySQLCon.query(sSQL, function(err, rows, fields) {
        if(err){
            console.log("An error ocurred performing the query.");
            return;
        }
        if (rows.length > 0) {
            console.log(rows[0].sField);
        } else {
            console.log("No Records found!");
        }
    });
    mySQLCon.end(function(){
        // The connection has been closed
    });
}

connectTest()

I'm using;

console.log(mySQLCon.state);

To see what the state of the connection is and it says 'disconnected'.

I don't get any errors when this runs it just doesn't do anything.

The database is on a remote PC, however I am using the same credentials to successfully connect to the database in other ways from this computer without any problems (navicat).

I tried running the code on the local database computer to see if that was the issue and it did the same thing, didn't connect and no errors.

Any help would be appreciated because I am totally lost without any errors to guide me and I'm doing what I think is correct!

Thanks

@D C you can refer my boilerplate , you can clear understanding about node and mysql connection – — yogesh agrawal
– yogesh agrawal, Commented Jan 10, 2018 at 17:15

halfer · Accepted Answer · 2020-08-18 15:30:36Z

2

There is two possibilities.

First of all, the connection is asynchronous, you should wait the connection to be explicitly over to do anything else.

Example:

mySQLCon.connect(function(err) {
    if(err){
        console.log(err.code);
        console.log(err.fatal);

        return;
    }

   console.log(mySQLCon.state);
   sSQL = "SELECT sField FROM tblName WHERE iID = 1";
   mySQLCon.query(sSQL, function(err, rows, fields) {
       if(err){
           console.log("An error ocurred performing the query.");
           return;
       }
       if (rows.length > 0) {
           console.log(rows[0].sField);
       } else {
           console.log("No Records found!");
       }
   });
   mySQLCon.end(function(){
       // The connection has been closed
   });
});

So the first possibility is that you never get any error because there is a timeout attached to the connection. So until the time is reached the function is going to hang.

It seems that you can change the timeout using the option connectTimeout: 1000000.

Second possibility is that it actually connect, and because you have no console.log telling you that you don't know. I refer you to the asynchronous problem I described to you just before.

edited Aug 18, 2020 at 15:30

halfer

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answered Jan 10, 2018 at 17:09

Orelsanpls

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6 Comments

yogesh agrawal Over a year ago

@D C you can refer my boilerplate , you can clear understanding about node and mysql connection

D C Over a year ago

Thanks Grégory, I appreciate your time to help me out, I had my code all inside the connect function in a previous test because I thought that it was due to node running it asyncronously. I've just reverted it back to what you suggested, and now when I run it it doesn't do anything inside that connect function, no error at all and it doesn't write the connection state into the console either, so it never gets to that line of code.

Orelsanpls Over a year ago

@DC so my guess is that it's trying to connect, and because it cannot succeed, it hang until the connection timeout get reached. To be sure about it, change the timeout to a small value like 5 sec. If that's the timeout you gonna have an error.

D C Over a year ago

@GrégoryNEUT Thanks, I tried the timeout and it makes no difference to how my code runs, it still appears to do nothing, is there anyway to step through the code?

D C Over a year ago

@GrégoryNEUT I think the problem is definitely because the code is continuing on and executing before my connection and recordset results are being returned, how can I get it to stop and wait until it has received those records?

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