Open Stack

Hi!

Excuse me, if the following question/problem is a basic one, already known problem, 
or even a bad setup on my side.

I just noticed that the most CPU consuming process in an idle 
OpenStack cluster is ceilometer-collector. When there are only 
10-15 samples/minute, it just constantly eats about 15-20% CPU. 

I started to debug, and noticed that it epoll()s constantly with a zero 
timeout, so it seems it just polls for events in a tight loop. 
I found out that the _maybe_ the python side of the problem is 
oslo_messaging.get_notification_listener() with the eventlet executor.
A quick search showed that this function is only used in aodh_listener and
ceilometer_collector, and both are using relatively high CPU even if they're
just 'listening'. 

My skills for further debugging is limited, but I'm just curious why this listener
uses so much CPU, while other executors, which are using eventlet, are not that
bad. Excuse me, if it was a basic question, already known problem, or even a bad
setup on my side.

Br,
György