Implement MongoDB TTL

[richardwilly98]

TTL should be implemented by the river

Please let me know if this feature would be useful.

[1] - http://docs.mongodb.org/manual/tutorial/expire-data/ [2] - http://www.elasticsearch.org/guide/reference/mapping/ttl-field/

[oakio]

It works now, because:

When the TTL thread is active, you will see delete operations in the output of db.currentOp() or in the data collected by the database profiler. (see: https://docs.mongodb.org/manual/core/index-ttl/#delete-operations)

but the ideal would be to have a TTL in ES and Mongodb