Add a Prometheus-compatible Histogram function, and convert the vmrange label to the le label

[greyireland]

No description provided.

[clementnuss]

any news here ? what can be done to help get this PR merged ?

[hagen1778]

Hello @greyireland @clementnuss!
I don't think it is a good idea to convert VictoriaMetrics histograms in Prometheus histograms because the former histograms are sparse with dynamic buckets. While standard Prometheus histograms are static and the whole logic for processing Prometheus histograms relies on that logic. For example, if instance A will produce 10 buckets for query latency histogram, and instance B will produce 11 buckets - the aggregation of 99th latency percentile for instance A and B will be calculated incorrectly.
So in fact, this change will result into confusion and incorrect processing results. Prometheus standard histograms should have static buckets across all application instances.

[Neal]

@hagen1778 that's a good point and in that case it may make more sense to add Prometheus style static buckets based Histogram in order to be fully compatible.

[vtolstov]

@Neal @greyireland do you plan to create fully prometheus compatible variant? my use-case - i don't like prometheus because it have many allocations with protobuf based structure creating, encoding...
but can't use vm metrics because on upper level i have only prometheus.
So i need fully compatible prometheus histogram support with predefined buckets across all services