Undefined "Connection" during database pooling in node js

Question

I am new to pooling in node js. I am trying to start a pool connection at crud_new_op.js file and export the connection to db_crud.js and log it in the console.

I tried different ways but i always get "undefined" for the connection that i export from the pool...

db_crud.js

var express = require('express');
var app = express();

var crud = require('./routes/crud_op_new.js');

app.get('/search',(req,res)=>{
console.log(crud.connection);
});

app.listen(8044);

crud_op_new.js

var mysql = require('mysql');

var conn = require('../config/db_config.js');

var db = conn.database;

var pool = mysql.createPool({
 connectionLimit : 100,
 host : db.host,
 user : db.user,
 password : db.password,
 database : db.database
});

pool.getConnection(function(err,connection){
 if(!err){
    exports.connection;
 }
 else {
    console.log("Error at pool creation");
 }
});

There i nothing wrong with database connection.

Adam · Accepted Answer · 2017-01-03 12:36:53Z

2

Why don't you just pass forward the pool.getConnection function?

// crud_op_new.js
exports.connection = pool.getConnection.bind(pool);

// db_crud.js
crud.connection(function (err, con) {
    if (err) throw err;
    console.log(con);
});

answered Jan 3, 2017 at 12:36

Adam

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1 Comment

digit Over a year ago

This should be the simplest way without passing any callback.

digit · Accepted Answer · 2017-01-03 12:31:47Z

0

You should return the connection

db_crud.js

var express = require('express');
var app = express();
var crud = require('./routes/crud_op_new.js');

app.get('/search',(req,res)=>{
 crud.connection(function (con) {
    console.log(con);
 });
});

app.listen(8044);

crud_op_new.js

var mysql = require('mysql');

var conn = require('../config/db_config.js');

var db = conn.database;

var pool = mysql.createPool({
 connectionLimit : 100,
 host : db.host,
 user : db.user,
 password : db.password,
 database : db.database
});

exports.connection = function (callback) {
  pool.getConnection(function(err,con){
    if(err) throw err;
    return callback(con);
  });
}

edited Jan 3, 2017 at 12:31

answered Jan 3, 2017 at 12:10

digit

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13 Comments

Adam Over a year ago

exports.connection() will still return undefined

digit Over a year ago

Nope. I have tried that. It will show connection object.

VisheshRaju Over a year ago

I am too getting same undefined

Adam Over a year ago

@digit, there is no return statement in your function which means i'll return undefined

digit Over a year ago

Oh. I just notice that you don't initiate connection. Where do you call create pool in db_crud.js

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