node.js won't connect to mysql

Question

Code:

var mysql = require('mysql');
var db_config = require('./db-config.json');

var connection = mysql.createConnection({
  host: db_config.host,
  user: db_config.user,
  port: db_config.port,
  password: db_config.password,
  database: db_config.database
});

connection.connect(function(err){
  if (!err) {
    console.log("Database is connected... \n\n");
  } else {
    console.log("Error connecting database \n\n" + err);
  }
});

connection.query('select 1+1 as solution', function(err, rows, fields){
  if(err) throw err;
  console.log('The solution is: ', rows[0].solution);

});

connection.end();

and my ./db-config.json is

{
"host": "**.*.**.***",
"user": "***",
"port": "13306",
"password": "****",
"database": "***"
}

and error is Error connecting database

Error: Connection lost: The server closed the connection.
C:\project\Nodejs\my-app\routes\db\dbtest.js:21
if(err) throw err;
^

Error: Connection lost: The server closed the connection.
at Protocol.end            (C:\project\Nodejs\node_modules\mysql\lib\protocol\Protocol.js:113:13)
at Socket.<anonymous>    (C:\project\Nodejs\node_modules\mysql\lib\Connection.js:109:28)
at emitNone (events.js:111:20)
at Socket.emit (events.js:208:7)
at endReadableNT (_stream_readable.js:1055:12)
at _combinedTickCallback (internal/process/next_tick.js:138:11)
at process._tickCallback (internal/process/next_tick.js:180:9)
--------------------
at Protocol._enqueue    (C:\project\Nodejs\node_modules\mysql\lib\protocol\Protocol.js:145:48)
at Protocol.handshake    (C:\project\Nodejs\node_modules\mysql\lib\protocol\Protocol.js:52:23)
at Connection.connect (C:\project\Nodejs\node_modules\mysql\lib\Connection.js:130:18)
at Object.<anonymous> (C:\project\Nodejs\my-app\routes\db\dbtest.js:12:12)
at Module._compile (module.js:643:30)
at Object.Module._extensions..js (module.js:654:10)
at Module.load (module.js:556:32)
at tryModuleLoad (module.js:499:12)
at Function.Module._load (module.js:491:3)
at Function.Module.runMain (module.js:684:10)

This is very strange because this database is already used in another program and its works just fine. I think the code itself is the problem because my local mysql has no problem.

I just start learning nodejs & express and at stuck at this very basic stage. Any help is appreciated.

Answer 1

You are ending the connection to the DB before the callbacks do their job.

var mysql = require('mysql');
var db_config = require('./db-config.json');

var connection = mysql.createConnection({
  host: db_config.host,
  user: db_config.user,
  port: db_config.port,
  password: db_config.password,
  database: db_config.database
});

connection.connect(function(err){
  if (err) {
    console.log("Error connecting database \n\n" + err);
    throw err
  } 
  connection.query('select 1+1 as solution', function(err, rows, fields){
    if(err) throw err;
    console.log('The solution is: ', rows[0].solution);
    connection.end();
    });
});

Callbacks don't execute immediately, they are asynchronous. Your code is getting to connection.end() before it has done all the async operations.