SetUp MongoDB Replication/Two way syncing Between two AWS Instances

Hi, I read many articles about mongodb master to slave or master to master architecture. We have two servers, each server has MongoDB Installed, My requirements is to have Master to master similar system, in which if Primary server is not working somehow, the route53 redirect all requests to DB Server2 . So has to be in SYNC between these two server. And whatever data gets collected ton DB Server2, it should automatically get synced with DB Server1 , as soon as it is available... this is just my proposition..If you are AWS expert, please let me know some open source and better solution for achieving the same.