Mongo river elasticsearch

hello,

I want to create river between Elasticsearch and mongo.
(http://www.codetweet.com/ubuntu-2/configuring-elasticsearch-mongodb/)
I have followed the whole procedure given in this link given above but still its not working for me. I want to create a replica set but it is giving me this error message
"> rs.initiate()
{
"info2" : "no configuration explicitly specified -- making one",
"errmsg" : "exception: bad --replSet config string format is: [/,,...]",
"code" : 13093,
"ok" : 0
}
".

Thankss in Advance,
please guys help me out.

Please keep it to one thread Elasticsearch river Monodb Error