Is there any way to observe each collection (or even one) in mongoDB? Now I think about timer to check document number or last Id, but maybe there is some possibility to implement mechanism like newDocumentAddedEvent?
There are no triggers in MongoDB (yet?), but if you're running a replica set (as you should), your app can pretend to be a catching-up secondary, tail the oplog collection and get information about new inserts/updates.
This is a very efficient approach (mongodb itself uses it for the replication).
来源：https://stackoverflow.com/questions/10754000/how-to-see-any-changes-new-row-in-mongodb