NodeJS - How to pass a mysql connection from main to child process? - mysql

Question

I tried the following server+worker code but it simply did not work.
server.js:
var net = require('net');
var mysql = require('mysql');
var cp = require('child_process');
var serverPort=20460;
var connection = mysql.createConnection({
database : 'test',
host : 'localhost',
user : 'root',
password : ''
});
var server = net.createServer(function (socket){
socket.on('data',function(data){
console.log("Server received: ",data);
var child = cp.fork('./worker');
child.send({'connection': connection});
});
});
connection.connect(function(err, two){
if (!err) {
server.listen(serverPort);
}
});
worker.js:
process.on('message', function(obj) {
//Will add more code to it later...
console.log("CHILD::Received: ",obj);
});
Gives me the following error at the child process' console.log():
JSON.stringify, avoid TypeError: Converting circular structure to JSON
Any suggestions ?

Answer 1

The way I'd do it is to have worker.js be the real "app" and the server.js just sets up the clustering. I've not tested this, but something along the lines of this:
// worker.js
var connection = require('./db');
var net = require('net');
var server = net.createServer(function (socket){
socket.on('data',function(data){
console.log("Server received: ",data);
connection.connect();
connection.query(/* your query here for inserting data */);
connection.end();
});
});
// db.js
var mysql = require('mysql');
var serverPort=20460;
var connection = mysql.createConnection({
database : 'test',
host : 'localhost',
user : 'root',
password : ''
});
module.exports = connection;
// server.js
var cluster = require('cluster');
var numCPUs = require('os').cpus().length;
if (cluster.isMaster) {
// Fork workers.
for (var i = 0; i < numCPUs; i++) {
cluster.fork();
}
cluster.on('exit', function(worker, code, signal) {
console.log('worker ' + worker.process.pid + ' died');
});
} else {
require('./worker');
}
For bonus points, you could use something like node-pool to create a connection pool, and have the db module return a connection from the pool instead.