In icehouse, usuage of the MongoDB aggregation pipeline framework for statistics queries was dropped in favor of a plain ol' map-reduce, due to ungraceful out-of-memory conditions arising out of the sorting/filtering logic in the 2.2-era MongoDB aggregation pipeline. Since these issues have been apparently resolved in MongoDB 2.6, the aggregation pipeline has been reinstated. This needs to be verified by QE to ensure that the out-of-memory problems are indeed resolved.
Tried statistics call with 1 million of samples. Packages: ceilometer*-5.0.2-2.el7ost.noarch mongodb*-2.6.11-1.el7ost.x86_64
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHEA-2016-0603.html