@@ -48,14 +48,22 @@ func NewMetrics(reg prometheus.Registerer, normMean, normDomain float64) *metric
4848 },
4949 []string {"service" },
5050 ),
51- // The same as above, but now as a histogram, and only for the normal
52- // distribution. The buckets are targeted to the parameters of the
53- // normal distribution, with 20 buckets centered on the mean, each
54- // half-sigma wide.
51+ // The same as above, but now as a histogram, and only for the
52+ // normal distribution. The histogram features both conventional
53+ // buckets as well as sparse buckets, the latter needed for the
54+ // experimental native histograms (ingested by a Prometheus
55+ // server v2.40 with the corresponding feature flag
56+ // enabled). The conventional buckets are targeted to the
57+ // parameters of the normal distribution, with 20 buckets
58+ // centered on the mean, each half-sigma wide. The sparse
59+ // buckets are always centered on zero, with a growth factor of
60+ // one bucket to the text of (at most) 1.1. (The precise factor
61+ // is 2^2^-3 = 1.0905077...)
5562 rpcDurationsHistogram : prometheus .NewHistogram (prometheus.HistogramOpts {
56- Name : "rpc_durations_histogram_seconds" ,
57- Help : "RPC latency distributions." ,
58- Buckets : prometheus .LinearBuckets (normMean - 5 * normDomain , .5 * normDomain , 20 ),
63+ Name : "rpc_durations_histogram_seconds" ,
64+ Help : "RPC latency distributions." ,
65+ Buckets : prometheus .LinearBuckets (normMean - 5 * normDomain , .5 * normDomain , 20 ),
66+ NativeHistogramBucketFactor : 1.1 ,
5967 }),
6068 }
6169 reg .MustRegister (m .rpcDurations )
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