OpenTelemetry Prometheus Text Exporter

A high-performance OpenTelemetry metrics exporter that converts metrics to Prometheus text exposition format.

Features

• High Performance: ~2.5-3x faster than existing implementations with ~2.0-2.5 million time series per second throughput
• Memory Optimized: Minimal allocations and memory footprint
• Prometheus Compliant: Generates valid Prometheus text exposition format
• Configurable: Flexible options for metric naming, units, and metadata
• Minimal Dependencies: Small dependency footprint with only essential crates (smartstring for optimization)

Supported Metric Types

• ✅ Gauges: All numeric types → Prometheus Gauge
• ✅ Sums: Cumulative+Monotonic → Counter, Cumulative+Non-monotonic → Gauge
• ✅ Histograms: All numeric types → Prometheus Histogram family
• ❌ Exponential Histograms: Currently unsupported (not supported by the Prometheus text exposition format)

Installation

Add this to your Cargo.toml:

[dependencies]
opentelemetry-prometheus-text-exporter = "0.1.0"
opentelemetry = "0.30"
opentelemetry_sdk = "0.30"

Quick Start

use opentelemetry::{KeyValue, metrics::MeterProvider};
use opentelemetry_sdk::metrics::SdkMeterProvider;
use opentelemetry_prometheus_text_exporter::PrometheusExporter;

// Create exporter with default configuration
let exporter = PrometheusExporter::new();

// Set up metrics provider
let provider = SdkMeterProvider::builder()
    .with_resource(
        opentelemetry_sdk::Resource::builder_empty()
            .with_attribute(KeyValue::new("service.name", "my-service"))
            .with_attribute(KeyValue::new("service.version", "1.0.0"))
            .build()
    )
    .with_reader(exporter.clone())
    .build();

// Create and use meters
let meter = provider.meter("my-meter");
let counter = meter.u64_counter("requests_total").build();
counter.add(1, &[KeyValue::new("method", "GET")]);

// Export metrics to Prometheus format
let mut output = Vec::new();
exporter.export(&mut output).unwrap();
println!("{}", String::from_utf8(output).unwrap());

Configuration Options

The exporter supports extensive configuration through the builder pattern:

use opentelemetry_prometheus_text_exporter::PrometheusExporter;

let exporter = PrometheusExporter::builder()
    .without_units()              // Disable unit suffixes in metric names
    .without_counter_suffixes()   // Disable _total suffixes on counters
    .without_target_info()        // Disable target_info metric from resources
    .without_scope_info()         // Disable otel_scope_info metrics
    .build();

Configuration Details

Output Format

The exporter generates standard Prometheus text exposition format:

# HELP target_info Target metadata
# TYPE target_info gauge
target_info{service_name="my-service",service_version="1.0.0"} 1
# HELP requests_total Total number of requests
# TYPE requests_total counter
requests_total{method="GET"} 1

Performance

This implementation is optimized for high-throughput scenarios:

• Throughput: ~2.0-2.5 million time series per second
• Memory: Minimal allocations and memory footprint
• Scaling: Linear performance with metric count and cardinality
• Overhead: Minimal configuration impact (< 5% difference between options)

Benchmarks

Run benchmarks to measure performance on your system:

# Quick benchmark
cargo bench --bench serialize -- --quick

# Full benchmark suite
cargo bench --bench serialize

# Compare against opentelemetry-prometheus
cargo bench --bench comparison

Why This Crate?

This crate was created to provide:

1. Better Performance: Significantly faster than existing OpenTelemetry Prometheus exporters
2. Text Format Focus: Specifically designed for Prometheus text exposition format
3. Memory Efficiency: Optimized memory usage patterns
4. API Compatibility: Drop-in replacement for existing exporters

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.

Links

• Repository
• Documentation
• Crates.io
• OpenTelemetry
• Prometheus