Comment 0 for bug 1506877

Currently in MOS Ceilometer use a javascript map-reduce command for getting a statistics requests. It works slow and only one Map-Reduce job can work on replicaset at a certain time.
So, it limit ceilometer usage for production usage.

We can improve situation with using aggregation pipeline instead of Map-Reduce. It doesn't block database and works more better than MR, but it need a MongoDB >= 2.6.

We have already backported it to MOS 7.0 in CR: https://review.fuel-infra.org/#/c/11049/