Currently, Metricbeat monitors MongoDB instances using Mongo's serverStatus() report. This is the primary "data dump" of information regarding a particular Mongo instance.
In addition, Mongo has other useful reporting tools that I think the broader user base would like to leverage. For starters, I think it would be great if Metricbeat is optionally capable of reporting on db.stats().
DB.stats() provides more granular insight into the host's resources utilized by a particular Mongo database. The fields are as follows:
"AvgObjSize": int
"Collections": int
"DataSize": int
"Db": string
"FileSize": int
"IndexSize": int
"Indexes": int
"NumExtents": int
"Objects": int
"Ok": int
"StorageSize": int
Db.stats() metrics are important for evaluating the host's resource usage for a particular database, and is very useful in sharding decisions/architectures.
I've currently implemented db.stats() reporting in the Community Beat, mongobeat and would like input from the community on adding db.stats() aggregation as part of Metricbeat's MongoDB module
If you're interested in the conversation, please refer to Mongobeat's initial pull request which discusses db.stats() in part.