Struct LabeledHistogram 

pub struct LabeledHistogram<L: LabelEnum> { /* private fields */ }

A histogram indexed by an enum label, providing O(1) dimensional metrics.

Each label variant has its own histogram with independent buckets.

Example

use fast_telemetry::{LabeledHistogram, LabelEnum};

#[derive(Copy, Clone, Debug)]
enum Endpoint { Api, Auth, Static }

impl LabelEnum for Endpoint {
    const CARDINALITY: usize = 3;
    const LABEL_NAME: &'static str = "endpoint";

    fn as_index(self) -> usize { self as usize }
    fn from_index(index: usize) -> Self {
        match index {
            0 => Self::Api, 1 => Self::Auth, _ => Self::Static,
        }
    }
    fn variant_name(self) -> &'static str {
        match self {
            Self::Api => "api", Self::Auth => "auth", Self::Static => "static",
        }
    }
}

let histogram: LabeledHistogram<Endpoint> = LabeledHistogram::with_latency_buckets(4);
histogram.record(Endpoint::Api, 150);    // 150µs
histogram.record(Endpoint::Auth, 2000);  // 2ms

// Iteration for export
for (label, buckets, sum, count) in histogram.iter() {
    println!("{}={}: count={}", Endpoint::LABEL_NAME, label.variant_name(), count);
}

Implementations

impl<L: LabelEnum> LabeledHistogram<L>

pub fn new(bounds: &[u64], shard_count: usize) -> Self

Create a labeled histogram with custom bucket boundaries.

Each label variant gets its own histogram with these boundaries.

pub fn with_latency_buckets(shard_count: usize) -> Self

Create a labeled histogram with default latency buckets (microseconds).

Buckets: 10µs, 50µs, 100µs, 500µs, 1ms, 5ms, 10ms, 50ms, 100ms, 500ms, 1s, 5s, 10s

pub fn record(&self, label: L, value: u64)

Record a value in the histogram for the given label.

pub fn get(&self, label: L) -> &Histogram

Get the histogram for a specific label (for detailed inspection).

pub fn iter(&self) -> impl Iterator<Item = (L, Vec<(u64, u64)>, u64, u64)> + '_

Iterate over all label/histogram data for export.

Returns (label, cumulative_buckets, sum, count) for each variant.

Trait Implementations

impl<L: LabelEnum> DogStatsDExport for LabeledHistogram<L>

fn export_dogstatsd( &self, output: &mut String, name: &str, tags: &[(&str, &str)], )

Export this metric to the output string in DogStatsD format.

impl<L: LabelEnum> OtlpExport for LabeledHistogram<L>

fn export_otlp( &self, metrics: &mut Vec<Metric>, name: &str, description: &str, time_unix_nano: u64, )

impl<L: LabelEnum> PrometheusExport for LabeledHistogram<L>

fn export_prometheus(&self, output: &mut String, name: &str, help: &str)

Export this metric to the output string.