Eoghan Glynn 7b58c1c9ea Wider selection of aggregates for mongodb ...

Partially-addresses: BP wider-aggregate-range

Support for two new aggregation functions has been added:

  * stddev: population standard deviation (unparameterized)
  * cardinality: count of distinct values for a sample attribute
    (parameterized by attribute name)

For example in order to calculate the standard deviation of CPU util:

  GET /v2/meters/cpu_util/statistics?aggregate.func=stddev

  HTTP/1.0 200 OK
  [{"aggregate": {"stddev": 0.6858829535841072},
    "duration_start": "2014-01-30T11:13:23",
    "duration_end": "2014-01-31T16:07:13",
    "duration": 104030.0,
    "period": 0,
    "period_start": "2014-01-30T11:13:23",
    "period_end": "2014-01-31T16:07:13",
    "groupby": null,
    "unit": "%"}]

Or to calculate the number of distinct instances that existed for
each tenant contrasted with the total number of instance samples
for that tenant in each 15 min period:

  GET /v2/meters/instance/statistics?aggregate.func=cardinality&aggregate.param=resource_id
                                    &aggregate.func=count
                                    &groupby=project_id&period=900

  HTTP/1.0 200 OK
  [{"count": 19,
    "aggregate": {"count": 19.0, "cardinality/resource_id": 3.0},
    "duration": 328.478029,
    "duration_start": "2014-01-31T10:00:41.823919",
    "duration_end": "2014-01-31T10:06:10.301948",
    "period": 900,
    "period_start": "2014-01-31T10:00:00",
    "period_end": "2014-01-31T10:15:00",
    "groupby": {"project_id": "061a5c91811e4044b7dc86c6136c4f99"},
    "unit": "instance"},
   {"count": 22,
    "aggregate": {"count": 22.0, "cardinality/resource_id": 4.0},
    "duration": 808.00384,
    "duration_start": "2014-01-31T10:15:15",
    "duration_end": "2014-01-31T10:28:43.003840",
    "period": 900,
    "period_start": "2014-01-31T10:15:00",
    "period_end": "2014-01-31T10:30:00",
    "groupby": {"project_id": "061a5c91811e4044b7dc86c6136c4f99"},
    "unit": "instance"},
   {"count": 2,
    "aggregate": {"count": 2.0, "cardinality/resource_id": 2.0},
    "duration": 0.0,
    "duration_start": "2014-01-31T10:35:15",
    "duration_end": "2014-01-31T10:35:15",
    "period": 900,
    "period_start": "2014-01-31T10:30:00",
    "period_end": "2014-01-31T10:45:00",
    "groupby": {"project_id": "061a5c91811e4044b7dc86c6136c4f99"},
    "unit": "instance"}]

Test coverage is provided by the scenario test added in
next patch of this series.

Change-Id: Id3a37622f35d9a7d757c485b4d486b3f01cc6474

2014-03-04 14:29:19 +00:00

5.9 KiB

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