Hello Gist

test.js

var sys = require('sys');
var exec = require('child_process').exec;
var zookeeper = require('node-zookeeper-client');

var root_shard_path = '/shard1';
var replSet = "arbiter";

function exists(client){
	client.exists(root_shard_path, 
				    function(event){
				  	console.log('Got event : %s.', event);
				  	exists(client, path);
				  },
				  	function(error, stat){
				  		if(error){
				  			console.log('Failed to check existence of node : %s due to : %s.', path, error );
				   		}

				   		if(stat){
				   			replication(client, root_shard_path, replSet);
				   		} else{
				   			shard(client, root_shard_path);
				   			replication(client, root_shard_path, replSet);
				   		}
				   		return;
				  } 
	);
}

function replication(client, path, replSet){
	client.create(path + "/" + replSet, new Buffer(''), zookeeper.CreateMode.EPHEMERAL, function(err, path){
		if(err){
			console.log('Failed to create node : %s due to %s', shard, err);
		}else{
			console.log('Node : %s is successfully created', shard );
		}
		return;
	});
}

function start() {

  var client = zookeeper.createClient('localhost:2181');

	client.once('connected', function () {
        exists(client);
	});

	client.connect();

    exec("mongod --port 20017 --dbpath /data/db/replSet_Arbiter --replSet Mongo_study --smallfiles --noprealloc --nojournal --logpath /data/db/replSet_Log/mongo-replSet_Arbiter.log", function(err, stdout, stderr) {
        console.log(stdout);
        client.close();
    });
}

start();