Revision as of 13:07, 28 January 2014

Horizon instance statistic query: pastebin horizon pdf

• fact1: "instance" meter reports 1 if the instance is _allocated_ regardless of the state of the instance. Except if the VM is in error state, in that case "instance" meter does not report sample.
• fact2: ceilometer does not have samples from the "instance" meter with counter_volume 0 for deleted instances obviously
• fact3: the state of the instance is not part of the metadata of the "instance" sample

Problem 1

So first you want to calculate avg(counter_volume) grouped by resource_id then make a sum(counter_volume) grouped by project_id. The avg(counter_volume) will produce invalid result for example if we have 6 measurement in an hour but the instance was running only half of the time, as we will have only 3 samples instead of 6 so the avg will be 1 instead of 1/2 due to fact2. If it is not a problem to get 1 instead of 1/2 for this case then you can use distinct instead of avg. The other possibility is to make the measurement period available on the API and just get sum(counter_volume) from the statistics API and then on the client side calculate the avg for the known period.

Problem 2

Your query with two group bys cannot be expressed in one SELECT statement. We have to translate the first avg (or distinct) step to a subquery of the second step. Our original idea for complex query statistic will allow multiple group bys but we haven't planned to allow such group bys that needs subqueries.