Cloned from launchpad blueprint https://blueprints.launchpad.net/ceilometer/+spec/exclude-low-sample-count.

Description:

Currently we have a potential scenario whereby an autoscaling alarm defined over an instance group, with the evaluation window & cooldown policy both on the short side, may fire prematurely if an outlier instance is one of just a small number reported as yet for the current period.

We should detect the case where the sample count is anomalously low for the most recent datapoints, based on say a variance of at least one standard deviation from the observed norm. In that case, the less reliable datapoint should be excluded from consideration for alarming.

Specification URL (additional information):

None