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| − | = Horizon instance statistic query =
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| − | [http://paste.openstack.org/show/54676/ pastebin]
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| − | [http://people.redhat.com/~lsurette/OpenStack/Horizon%20Overview%20Pages_v1.0.pdf horizon pdf]
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| − | * 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.
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| − | * fact2: ceilometer does not have samples from the "instance" meter with counter_volume 0 for deleted instances obviously
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| − | * fact3: the state of the instance is not part of the metadata of the "instance" sample
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| − | == Problem 1 ==
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| − | So first you want to calculate avg(counter_volume) grouped by resource_id then make a sum(counter_volume) grouped by project_id.
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| − | 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.
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| − | == Problem 2 ==
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| − | 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.
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| − | == Problem with DISTINCT ==
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| − | SELECT count(*), project_id FROM ( SELECT DISTINCT resource_id, project_id FROM Meter) GROUP BY project_id
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| − | SELECT count(*), project_id FROM (SELECT avg(counter_volume), resource_id, project_id FROM Meter GROUP BY resource_id, project_id) GROUP BY project_id
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| − | ==>>
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| − | SELECT count(DISTINCT(resource_id, project_id)) FROM Meter GROUP BY project_id
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| − | * Only the count function is meaningful
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| − | * Only the instance meter can be aggregated this way
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| − | * Only the resource_id, project_id seems a valid DISTINCT parameter ???
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| − | = TODO =
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| − | Gauge VM state counter https://blueprints.launchpad.net/ceilometer/+spec/state-meter
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| − | Propose separate sub meter like instance:active, instance:stopped for clarity
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