one worker listen to event in nodejs

Question

I want to use Cluster module of nodejs but when event trigger,when the first worker capture it,other ones don't do anything.

var cluster     =   require('cluster')
    numCPUs     =   require('os').cpus().length;

if (cluster.isMaster){
    for (var i = 0; i < numCPUs; i++)
        cluster.fork();

    cluster.on('exit', function(worker, code, signal) {
        cluster.fork();
    });
} else {
    var redis   =   require('redis');
    var client  =   redis.createClient();
    client.on('message',function(channel,message){
        console.log(channel,message);
    });
    client.subscribe("CH_IP");    
}

The above code has below output

CH_IP {"LOC":"OTHER","PID":1,"SID":1}
CH_IP {"LOC":"OTHER","PID":1,"SID":1}
CH_IP {"LOC":"OTHER","PID":1,"SID":1}
CH_IP {"LOC":"OTHER","PID":1,"SID":1}
CH_IP {"LOC":"OTHER","PID":1,"SID":1}
CH_IP {"LOC":"OTHER","PID":1,"SID":1}
CH_IP {"LOC":"OTHER","PID":1,"SID":1}
CH_IP {"LOC":"OTHER","PID":1,"SID":1}

How to edit code to only run one console.log?

Answer 1

The fork method accepts an object of key/pair values, which gets added to the workers process environment. You can use this to identify each worker, and single out one to do the work:

if (cluster.isMaster){
    for (var i = 0; i < numCPUs; i++)
        cluster.fork({ workerId: i+1 });
    // etc...
} else {
    if(process.env.workerId == 1){
        // do stuff
    }
}