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Simple message passing between cluster master and workers in Node.js
var cluster = require('cluster');
if (cluster.isWorker) {
console.log('Worker ' + process.pid + ' has started.');
// Send message to master process.
process.send({msgFromWorker: 'This is from worker ' + process.pid + '.'})
// Receive messages from the master process.
process.on('message', function(msg) {
console.log('Worker ' + process.pid + ' received message from master.', msg);
});
}
if (cluster.isMaster) {
console.log('Master ' + process.pid + ' has started.');
// Fork workers.
for (var i = 0; i < 2; i++) {
var worker = cluster.fork();
// Receive messages from this worker and handle them in the master process.
worker.on('message', function(msg) {
console.log('Master ' + process.pid + ' received message from worker ' + this.pid + '.', msg);
});
// Send a message from the master process to the worker.
worker.send({msgFromMaster: 'This is from master ' + process.pid + ' to worker ' + worker.pid + '.'});
}
// Be notified when worker processes die.
cluster.on('death', function(worker) {
console.log('Worker ' + worker.pid + ' died.');
});
}
@adrianseeley

thanks! great ref.

@jnovack

This won't work. var inside for?

worker will hold the last worker forked, not each one (specially inside the event callback).

@dazld

should work fine, as the variable is only being used inside that particular block. if it was leaking outside the block, then yes, it would be a problem (and should be in a closure, or have some kind of binding). nice example, thanks!

@ynkm169

how do u pass message between workers.....pass message to master makes master a bottleneck..............

@CubixSystem

Good example.
Need to replace this.pid for this.process.pid on newer Node versions.
Same for worker.pid

@chbdetta

Great example. Thanks a lot!

@danieldram
danieldram commented Jun 10, 2016 edited

can use os.cpus().length to get number of running workers if you do not know the exact number as indicated in the for loop.
(Be sure to var os = require('os') when using)

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