Understanding histogram_quantile based on rate in Prometheus

Question

According to Prometheus documentation in order to have a 95th percentile using histogram metric I can use following query:

histogram_quantile(0.95, sum(rate(http         


        

Answer 1

You can refer to my reply here

Actually the rate() function is just used to specify the time window, the denominator has no effect in the computation of the pecentile value.

Answer 2

You have to use reset because counters can be reset, rate automatically considers resets and give you the right count for each second. Just remember that always use rate before using counters.

Answer 3

I believe this is the code for it in prometheus
The general idea is that you use the data in the buckets to extrapolate / approximate the quantiles Elasticsearch also does something similar (yet different/much simpler) in their rollup capabilities