Node.js: Cannot call method release of undefined (MySql) - mysql

Question

So great part of this is that this same code works on my development machine.
I'm trying to deploy it to the production server, and i'm getting this error:
Cannot call method release of undefined.
This works on my box, so why is that not working in production is what confuses me.
I downloaded the code with all the modules, then tried to do npm install, and still manually deploy express and mysql, but no luck.
The infringing line is:
connection.release();
If i rem that line, then it will just hang on anything trying to call connection.
The code:
process.env.TZ = 'UTC';
var express = require("express");
var mysql = require('mysql');
var pool = mysql.createPool({
connectionLimit : 100, //important
host : 'localhost',
user : 'thedbuser',
password : 'thedbpass',
database : 'thedatabase',
debug : false,
timezone: 'utc'
});
var app = express();
function get_data(req,res) {
pool.getConnection(function(err,connection){
if (err) {
connection.release();
res.json({"code" : 100, "status" : "Error in connection database"});
return;
}
console.log('connected as id ' + connection.threadId);
var id = Number(req.param("id"));
connection.query("select * from thetable WHERE id = ?" , [id], function(err,rows){
connection.release();
if(!err) {
res.json(rows);
}
});
connection.on('error', function(err) {
res.json({"code" : 100, "status" : "Error in connection database"});
return;
});
});
}
app.get("/id",function(req,res){
get_data(req,res);
});
app.listen(3000);

Answer 1

pool.getConnection(function(err,connection){
if (err) {
connection.release();
res.json({"code" : 100, "status" : "Error in connection database"});
return;
}
So inside the if (err) block means there was an error. The node.js generic callback API semantic is when an err is passed to the callback function, the success/result variable is not guaranteed to also be provided. In this case, since there was an error getting a connection, no connection object is passed to the callback - because the error prevented the connection from happening correctly. Thus you can probably safely just delete the connection.release() line but if you know there is a case where both err and connection will both be passed (I suspect there is no such case), you could guard your call to connection.release() with an if (connection) block or a logical operator like connection && connection.release()