Rollup & aggregation
- Aggregation: aggregate datapoints with different tags grouped by a query into 1 datapoint
- Rollup: roll up datapoints with the same tags in a rollup interval to reduce datapoints to show by a query.
- By default, an hour long query shows a point every twenty seconds, while a four hour graph shows a point every minute.
Rollup interval: enforced vs custom
When graphing, Datadog sets a limit on the number of points per timeseries. To retain visual clarity, a series can have up to 1500 points. To respect this limit, Datadog rolls up datapoints automatically, defaulting to the avg method, effectively displaying the average of all datapoints within a time interval for a given metric.
Queries for COUNT and RATE type metrics have the .as_count() modifier appended automatically in the UI, which sets the rollup method used to sum and disables interpolation.
- For “Count” metric type, effect of
as_count()is disables any interpolation and sets the time aggregator to SUM. - For “Gauge” metric type,
as_count()andas_rate()have no effect.
DDSketch
Computing Accurate Percentiles with DDSketch