Node.js cluster get master PID

Node.js cluster get master PID

I used following cluster code to fork multiple process for my node app.
if (cluster.isMaster) {
require('os').cpus().forEach(function () {
cluster.fork();
});
cluster.on('exit', function (worker, code, signal) {
cluster.fork();
});
} else if (cluster.isWorker) {
logger.log.info('Worker server started on port %d (ID: %d, PID: %d)',
app.get('port'), cluster.worker.id, cluster.worker.process.pid);
}
the output is:
Thu Sep 05 2013 20:30:03 GMT-0700 (PDT) - info: Worker server started on
port 3000 (ID: 1, PID: 606)
Thu Sep 05 2013 20:30:03 GMT-0700 (PDT) - info: Worker server started on
port 3000 (ID: 2, PID: 607)
Thu Sep 05 2013 20:30:03 GMT-0700 (PDT) - info: Worker server started on
port 3000 (ID: 5, PID: 610)
Thu Sep 05 2013 20:30:03 GMT-0700 (PDT) - info: Worker server started on
port 3000 (ID: 3, PID: 608)
Thu Sep 05 2013 20:30:03 GMT-0700 (PDT) - info: Worker server started on
port 3000 (ID: 4, PID: 609)
Thu Sep 05 2013 20:30:03 GMT-0700 (PDT) - info: Worker server started on
port 3000 (ID: 6, PID: 611)
Thu Sep 05 2013 20:30:03 GMT-0700 (PDT) - info: Worker server started on
port 3000 (ID: 8, PID: 613)
Thu Sep 05 2013 20:30:03 GMT-0700 (PDT) - info: Worker server started on
port 3000 (ID: 7, PID: 612)
There is 8 worker processes but when I checked process using pgrep, I saw 9
$ pgrep -l node
613 node
612 node
611 node
610 node
609 node
608 node
607 node
606 node
605 node
so one process extra must be master process and how do I print out the
master process IP?
Thanks