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histogram_metrics_helper: support native histogram

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approx_exponential_histogram uses similar logic to Prometheus native
histogram, to allow Prometheus sending its data in a native histogram
format it needs to report schema and min id (id of the first bucket).

This patch update to_metrics_histogram to set those optional parameters,
leaving it to the Prometheus to decide in what format the histogram will
be reported.

Signed-off-by: Amnon Heiman <amnon@scylladb.com>
This commit is contained in:
Amnon Heiman
2024-01-09 16:09:01 +02:00
parent fc9bd2de03
commit 95d1146fea
1 changed files with 3 additions and 1 deletions
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4
utils/histogram_metrics_helper.hh
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@@ -19,10 +19,12 @@
template<uint64_t Min, uint64_t Max, size_t Precision>
seastar::metrics::histogram to_metrics_histogram(const utils::approx_exponential_histogram<Min, Max, Precision>& hist) {
seastar::metrics::histogram res;
static constexpr size_t MIN_ID = log2ceil(Min) * Precision + 1;
static constexpr size_t Schema = log2floor(Precision);
res.buckets.resize(hist.size() - 1);
uint64_t cummulative_count = 0;
res.sample_sum = 0;
res.native_histogram = seastar::metrics::native_histogram_info{Schema, MIN_ID};
for (size_t i = 0; i < hist.NUM_BUCKETS - 1; i++) {
auto& v = res.buckets[i];
v.upper_bound = hist.get_bucket_lower_limit(i + 1);