Comment 13 for bug 1551667

We have two scenarios with and without batch enabled in Ceilometer:

* Without I think the oslo.messaging rabbit_qos_prefetch_count default (0 read ahead a ton of messages) is not good for ceilometer. It's configurable only since Newton.
  So even you reduce the executor threads if you queue is really big you can still have a high memory usage because of prefetching.

* With batch enabled oslo.messaging default are currently set as following:
  executor thread = 1 and prefetch = batch_size, so memory usage should be good in this case.