Crate fast_telemetry 

Fast, thread-sharded counters and histograms for high-performance telemetry.

OpenTelemetry counters use atomic operations with global synchronization, which causes cache-line bouncing across cores. This crate provides thread-local sharded counters that:

• Increment with no cross-thread contention (just a thread-local write)
• Are cache-line padded to avoid false sharing (using crossbeam’s CachePadded)
• Aggregate on read (sum all shards)

Labeled Metrics

For dimensional metrics (counters/gauges/histograms broken down by label), use the Labeled* types with a LabelEnum implementation. These provide O(1) lookup via array indexing instead of HashMap lookups.

use fast_telemetry::{LabeledCounter, LabelEnum};

#[derive(Copy, Clone, Debug)]
enum HttpMethod { Get, Post, Put, Delete }

impl LabelEnum for HttpMethod { /* ... */ }

let counter: LabeledCounter<HttpMethod> = LabeledCounter::new(4);
counter.inc(HttpMethod::Get);  // O(1) array index, no hashing

Re-exports

pub use span::CompletedSpan;

pub use span::Span;

pub use span::SpanAttribute;

pub use span::SpanCollector;

pub use span::SpanEvent;

pub use span::SpanId;

pub use span::SpanKind;

pub use span::SpanStatus;

pub use span::SpanValue;

pub use span::TraceId;

pub use span::current_span_id;

pub use span::current_trace_id;

Modules

otlp

span

Standalone distributed tracing for fast-telemetry.

Structs

Counter

A sharded atomic counter.

Distribution

Exponential histogram distribution for high-performance metric recording.

DynamicCounter

Counter keyed by runtime label sets.

DynamicCounterSeries

A reusable handle to a dynamic-label counter series.

DynamicDistribution

Distribution keyed by runtime label sets.

DynamicDistributionSeries

A reusable handle to a dynamic-label distribution series.

DynamicGauge

Gauge keyed by runtime label sets.

DynamicGaugeI64

Signed integer gauge keyed by runtime label sets.

DynamicGaugeI64Series

A reusable handle to a dynamic-label i64 gauge series.

DynamicGaugeSeries

A reusable handle to a dynamic-label gauge series.

DynamicHistogram

Histogram keyed by runtime label sets.

DynamicHistogramSeries

A reusable handle to a dynamic-label histogram series.

DynamicLabelSet

Canonicalized runtime label set.

Gauge

A cache-padded atomic gauge for point-in-time measurements.

GaugeF64

A cache-padded atomic gauge for floating-point point-in-time measurements.

Histogram

A fixed-bucket histogram with thread-sharded counters.

LabeledCounter

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

LabeledGauge

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

LabeledHistogram

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

Enums

Temporality

Aggregation temporality used during export.

Traits

DogStatsDExport

Trait for exporting a metric in DogStatsD format.

LabelEnum

Trait for label enums used with LabeledCounter, LabeledGauge, etc.

OtlpExport

Trait for exporting a metric as OTLP protobuf Metric messages.

PrometheusExport

Trait for exporting a metric in Prometheus text exposition format.

Functions

advance_cycle

Advance the eviction cycle by 1 and return the new value.

current_cycle

Get the current eviction cycle.

Derive Macros

DeriveLabel

Derive macro for implementing LabelEnum on enums.

ExportMetrics

Derive macro for exporting metrics in Prometheus, DogStatsD, and OTLP formats.