Interesting usage of the MongoDB oplog to replace the lack of storage notifications:
ElasticSearch has a built in feature of Rivers, which are essentially plugins for specific services to constantly stream in new updates for indexing. Unfortunately, there’s no MongoDB River (probably due to the lack of built-in database triggers), so I did some research and realized that I could use the MongoDB oplog to continually capture updates to our main databases.
Kristina Chodorow has two posts—here and here—detailing what’s stored in the oplog.
Original title and link: Real-Time Search With MongoDB and Elasticsearch ( ©myNoSQL)