Metrics Aggregations: custom stats functions, script stats, user-defined metrics, custom metrics


(Jin Huang) #1

Hi people,

Can someone provide some detailed information on how to extend the sets of
currently available metrics in the aggregation framework?

For now, Elasticsearch provides support for the metrics: count, min, max,
avg, sum, sum_of_squares, variance, and std_deviation. How can I define my
own?

I understand that there might some hard constraints on the type of metrics
could be defined. But it would be nice if someone can provide a simple
example of how to write my own.

Here is a couple of suggested examples that I would want to know how to
write:

  1. I want to calculate all the n-th central moments, with n=2,3,4,..10. By
    the way, Elasticsearch already provides the 2nd central moment, i.e. square
    of the standard deviation.
  2. I want to get the second order statics. That is, I want to the second
    smallest number.

In general, I would like to know what kind of custom aggregator is easy to
write? If the above examples require a deep dive into some of the source
codes, please DO! I don't mind if the answer runs 10 pages long as long as
someone can provide me with some pointers on how to get started.

Thanks,
Jin

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(system) #2