domain-cluster-example.js

var cluster = require('cluster');
var PORT = +process.env.PORT || 1337;

if (cluster.isMaster) {
  // In real life, you'd probably use more than just 2 workers,
  // and perhaps not put the master and worker in the same file.
  cluster.fork();
  cluster.fork();

  cluster.on('disconnect', function(worker) {
    console.error('disconnect!');
    cluster.fork();
  });

} else {
  // the worker
  var domain = require('domain');

  var server = require('http').createServer(function(req, res) {
    var d = domain.create();
    d.on('error', function(er) {
      console.error('error', er.stack);

      // note: we're in dangerous territory now!
      try {
        // make sure we close down within 30 seconds
        var killtimer = setTimeout(function() {
          process.exit(1);
        }, 30000);
        // But don't keep the process open just for that!
        killtimer.unref();

        // stop taking new requests.
        server.close(function() {
          console.error('server no longer listening');
        });

        // let the master know we're through.  This will trigger a
        // 'disconnect' in the cluster master, and then it will fork
        // a new worker.
        cluster.worker.disconnect();

        // try to send an error to the request that triggered the problem
        res.statusCode = 500;
        res.setHeader('content-type', 'text/plain');
        res.end('Oops, there was a problem!\n');
      } catch (er2) {
        // oh well?
        console.error('Error sending 500!', er2.stack);
      }
    });

    // because req and res were created before this domain existed,
    // we need to explicitly add them.
    d.add(req);
    d.add(res);

    // Now run the handler function.
    d.run(function() {
      handleRequest(req, res);
    });
  });
  server.listen(PORT);
}

function handleRequest(req, res) {
  switch(req.url) {
    case '/error':
      setTimeout(function() {
        // this is the error
        flerb.bark();
      });
      break;
    default:
      res.end('ok');
  }
}