[openstack-dev] [Ceilometer]Cumulative metrics resetting

Adrian Turjak adriant at catalyst.net.nz
Wed Jan 29 23:12:32 UTC 2014

A question about this bug:

In the billing program we are currently writing we've partly accounted 
for resetting of values in a given period for the cumulative metrics, 
but since we need high accuracy especially for metrics like 
network.incoming/outgoing, we are likely to lose chargeable data if 
someone resets a VM, or a VM goes down.

10min pipeline interval, a reset/shutdown happens 7 mins after the last 
poll. The data for those 7 mins is gone. Even terminating a VM will mean 
we lose the data in that last interval.

Fixing the bug so resets don't happen is likely a lot of work, and I 
have a feeling will require work in Nova, and probably won't account for 
the terminate case.

On the other hand, would it be possible to setup a notification based 
metric that updates cumulative metrics, or triggers a poll right before 
the reset/shutdown/suspension/terminate, so we have an entry right 
before it resets and don't lose any data? This would pretty much solve 
the issue, and as long as it is documented that the cumulative metrics 
reset, this would solve most problems.

Since the 'process_notification' function only gets passed a 'message', 
I don't know if there is a way to pull the needed data out from nova 
using only what is in the message though.

Any thoughts, or suggestions as to where to start experimenting?

-Adrian Turjak

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