Debugging Node.js processes with cluster.fork()

Question

I've got some code that looks very much like the sample in the Cluster documentation at http://nodejs.org/docs/v0.6.0/api/cluster.html, to wit:

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

if (cluster.isMaster) {
  var i;
  // Master process
  for (i = 0; i < numCPUs; i++) {
    cluster.fork();
  }
  cluster.on('death', function (worker) {
    console.log('Worker ' + worker.pid + ' died');
  });
} else {
  // Worker process
  server.createServer({port: 80}, function(err, result) {
    if (err) {
      throw err;
    } else {
      console.log('Thread listening on port ' + result.port);
    }
  });
}

I've installed node-inspector and tried using both it and the Eclipse V8 plugin detailed at https://github.com/joyent/node/wiki/Using-Eclipse-as-Node-Applications-Debugger to debug my application, but it looks like I can't hook a debugger up to forked cluster instances to put breakpoints at the interesting server logic--I can only debug the part of the application that spawns the cluster processes. Does anybody know if I can in fact do such a thing, or am I going to have to refactor my application to use only a single thread when in debugging mode?

I'm a Node.js newbie, so I'm hoping there's something obvious I'm missing here.

Answer 1

var fixedExecArgv=[];
fixedExecArgv.push('--debug-brk=5859');
cluster.setupMaster({ 
  execArgv: fixedExecArgv 
});

Credit goes to Sergey's post.

I changed my server.js to fork only one worker mainly for testing this then added the code above the forking. This fixed the debugging issue for me. Thank you Sergey for explaining and providing the solution!!!