MongoDB - Finding Slow Operations

db.currentOp()
db.currentOp({"secs_running" : { "$gt" : 2 }})

currentOp.client can give you the IP and Port of where the query originated from.
(in our case, we have many Services....... this can help isolate commands coming from a specific Service)

http://docs.mongodb.org/manual/reference/method/db.currentOp/#db.currentOp