Am 22.09.25 um 07:50 schrieb Nguyễn Hữu Khôi:
> Hello,
>
> I would like to understand how the evaluation process works.
>
> For example, I have this rule:
>
> |openstack alarm create --name memory_use_test \ --type
> gnocchi_resources_threshold \ --metric memory.usage \ --threshold 102 \
> --comparison-operator gt \ --aggregation-method mean \ --granularity 60
> \ --evaluation-periods 3 \ --resource-id dca36039-c603-422c-8366-
> f6ba4e9539c3 \ --resource-type instance |
>
> Does this mean that when the |alarm-evaluator| service is running per a
> period, it will check the last 3 data points, each aggregated over 60
> seconds?
>
> Thank you. Regards.
>
>
> Nguyen Huu Khoi


The evaluation process is quite simple, it checks if a given condition
is met.

What you need to know is that the granularity here is used as parameter
for metrics stored in gnocchi
In plain English, this is asking for "give me the metrics you stored in
a 60 seconds granularity" and evaluate it over the last three periods.

Caution: If gnocchi does not have metrics stored in 60 seconds
granularity, but for example in 15 secs granularity, it will still
return "not enough data".

I blogged about this quite some time ago
https://matthias-runge.de/2021/12/06/debugging-openstack-metrics/
Matthias