mongodb - Expire a Collection in Mongo using Casbah EnsureIndex -

i attempting expire collection in mongo using casbah's ensureindex api.

based on document http://docs.mongodb.org/manual/tutorial/expire-data/

i using casbah's proposed ensureindex api

 collection.ensureindex(dbobject("status" -> 1, "expireafterseconds" -> 120)) 

to expire collection in 2 minutes ...

the collection not being evicted or expired.

am missing else here?

thanks

there couple things check:

1. were following docs t , tried create index on status field doesn't exist in documents? (had atleast ask...)
2. does status field contain dates? can theoretically mixed, documents date type considered expiration.
3. have checked collection indexes make sure index created?

to check index console run: db.collection.getindexes(). if index created successfully, double check have corresponding status fields in documents , proper dates.

adding index alone, doesn't create date field - need add documents or use existing date field not part of other index.

also note, docs:

ttl indexes expire data removing documents in background task runs every 60 seconds

so, if have 120 second expiration, bear in mind, possible documents remain 120 seconds 179 seconds, give or take, depending on when document expired , background task last ran.

edit: noted in comments - collection cannot removed based on ttl index, index expires documents in collection.