mongodb - "replication oplog window" possibly reduced due to profiling - when profiling disabled no change?

Question

PROBLEM

I have a 3 member replica set (no sharding) running mongodb version 2.4.8.

Using MMS (Mongo Monitoring) I can see that on 7th July 2014 at 12:00 my "replication oplog window" dropped from 2777.78 hours to 68 hours at its lowest point.

Looking back at my log of changes on this date I can see database profiling was enabled that morning.

"db.setProfilingLevel(0)" to disable profiling was executed an hour ago on all collections and on all members of the replica set (PRIMARY FIRST).

QUESTION

An hour later my "replication oplog window" counter is still showing only 102 hours. Will this take time to increase again or should I be looking for another cause ?

Thank you Scott

Answer 1

OK, i think i know the answer. The OPLOG collection is a capped collection. It overwrites over time. The profile level was set to 2 for a short period of time logging all operations. I guess it will take time to overwrite these operations on a capped collection again and as a result increase the op log window.

Would be interested in anyone elses take on this issue.

Thank you.