Monstache: realtime MongoDB to ElasticSearch replication

connector allows one to select the fields which are replicated but monstache goes a bit further by integrating the Otto embedded javascript engine. This allows for modifying or adding fields in addition to dropping at the collection level. It appears connector's field option is global to all collections. monstache also has a stateful mode (using the resume flag) which allows one to replay only the events missed since the last run. Another alternative is transporter from compose which is also has the Otto engine and is written in Go. However, monstache is a single purpose tool while transport is a more generic tool.