NodeJS|Cluster: How to send data from master to all or single child/workers?

Question

I have working (stock) script from node var cluster = require('cluster'); var http = require('http'); var numReqs = 0; if (cluster.isMaster) { // Fork workers. for (var i = 0; i < 2; i++) { var worker = cluster.fork(); worker.on('message', function(msg) { if (msg.cmd && msg.cmd == 'notifyRequest') { numReqs++; } }); } setInterval(function() { console.log("numReqs =", numReqs); }, 1000); } else { // Worker processes have a http server. http.Server(function(req, res) { res.writeHead(200); res.end("hello world\n"); // Send message to master process process.send({ cmd: 'notifyRequest' }); }).listen(8000); } In the above script I can send data from worker to master process with ease. But how to send data from master to the worker/workers? With examples, if it possible. JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

Because cluster.fork is implemented on top of child_process.fork, you can send messages from a master to the worker by using worker.send({ msg: 'test' }), and from a worker to a master by process.send({ msg: 'test' });. You receive the messages like so: worker.on('message', callback) (from worker to master) and process.on('message', callback); (from master to worker). Here's my full example, you can test it by browsing http://localhost:8000/ Then the worker will send a message to the master and the master will reply: var cluster = require('cluster'); var http = require('http'); var numReqs = 0; var worker; if (cluster.isMaster) { // Fork workers. for (var i = 0; i < 2; i++) { worker = cluster.fork(); worker.on('message', function(msg) { // we only want to intercept messages that have a chat property if (msg.chat) { console.log('Worker to master: ', msg.chat); worker.send({ chat: 'Ok worker, Master got the message! Over and out!' }); } }); } } else { process.on('message', function(msg) { // we only want to intercept messages that have a chat property if (msg.chat) { console.log('Master to worker: ', msg.chat); } }); // Worker processes have a http server. http.Server(function(req, res) { res.writeHead(200); res.end("hello world\n"); // Send message to master process process.send({ chat: 'Hey master, I got a new request!' }); }).listen(8000); }