metrics-lib 0.9.4

Latest local Criterion means (cargo bench --bench metrics_bench --all-features, Windows x86_64, Rust stable). Numbers are for the cached-handle hot-path pattern (hold an Arc<Counter> / Arc<Gauge> / … and call .inc() / .set() directly):

• Counter increment: ~1.5 ns/op
• Gauge set: ~0.4 ns/op
• Timer record: ~3 ns/op
• Histogram observe: ~10 ns/op (depends on bucket count)
• Memory: 64 bytes per metric (cache-aligned)

Calling metrics().counter("name").inc() per call (global lookup) is slower — it pays for an RwLock::read() + HashMap::get(&str) + Arc::clone(). The cached_vs_global Criterion group reports both numbers side-by-side; cache the Arc in hot loops.

Features

Core Metrics

• 🔢 Counters — atomic increment/decrement with overflow-safe try_* variants
• 📊 Gauges — IEEE 754 atomic floating-point with non-finite guards
• ⏱️ Timers — nanosecond precision with RAII guards and batch recording
• 📈 Rate Meters — tumbling-window rates with burst detection and API limiting
• 📐 Histograms (v0.9.3) — bucketed observations with sum/count + quantile estimation
• 🏷️ Labels (v0.9.3) — LabelSet with bounded cardinality cap (default 10 000)
• 💾 System Health — background-sampled CPU / memory / load / threads / FDs / health score (v0.9.4: zero-contention reads)

Telemetry & Exporters (v0.9.3+)

Five built-in exporters render the registry into the format your backend speaks:

All exporters honour LabelSet and MetricMetadata (help text + unit + kind) — # HELP / # TYPE / # UNIT lines, OTLP description / unit, StatsD tags.

End-to-end runnable demos: labels_demo, histogram_latency, prometheus_endpoint, statsd_push, otlp_push, snapshot_serde.

Advanced Features

• Hot-path lock-free — pure atomic operations on every increment/record/observe
• Async Native — first-class async/await support with zero-cost abstractions
• Resilience — circuit breakers, adaptive sampling, backpressure control
• Cross-Platform — Linux (/proc), macOS, Windows (sysinfo)
• Cache-Aligned — 64-byte alignment prevents false sharing

API Overview

For a complete reference with examples, see docs/API.md.

• Counter — ultra-fast atomic counters with batch and conditional ops
• Gauge — atomic f64 gauges with math ops, EMA, and min/max helpers
• Timer — nanosecond timers, RAII guards, and closure/async timing
• RateMeter — tumbling-window rate tracking and bursts
• Histogram — bucketed observations with sum/count and approximate quantiles (v0.9.3)
• LabelSet — labeled metric instances with bounded cardinality (v0.9.3)
• SystemHealth — CPU, memory, load, threads, FDs, health score
• Exporters — Prometheus, OpenMetrics, JSON snapshot, StatsD UDP, OTLP/HTTP+JSON (v0.9.3)
• Async support — AsyncTimerExt, AsyncMetricBatch
• Adaptive controls — sampling, circuit breaker, backpressure
• Prelude — convenient re-exports

Error handling: try_ variants

All core metrics expose non-panicking try_ methods that validate inputs and return Result<_, MetricsError> instead of panicking:

• Counter: try_inc, try_add, try_set, try_fetch_add, try_inc_and_get
• Gauge: try_set, try_add, try_sub, try_set_max, try_set_min
• Timer: try_record_ns, try_record, try_record_batch
• RateMeter: try_tick, try_tick_n, try_tick_if_under_limit

Error semantics:

• MetricsError::Overflow — arithmetic would overflow/underflow an internal counter.
• MetricsError::InvalidValue { reason } — non-finite or otherwise invalid input (e.g., NaN for Gauge).
• MetricsError::OverLimit — operation would exceed a configured limit (e.g., rate limiting helpers).

Example:

use metrics_lib::{init, metrics, MetricsError};

init();
let c = metrics().counter("jobs");
c.try_add(10)?;      // Result<(), MetricsError>
let r = metrics().rate("qps");
let allowed = r.try_tick_if_under_limit(1000.0)?; // Result<bool, MetricsError>

Panic guarantees: the plain methods (inc, add, set, tick, etc.) prioritize speed and may saturate or assume valid inputs. Prefer try_ variants when you need explicit error handling.

Installation

Add to your Cargo.toml:

[dependencies]
metrics-lib = "0.9.4"

# Optional features
metrics-lib = { version = "0.9.4", features = ["async"] }

# Full feature set (stable + async + serde)
metrics-lib = { version = "0.9.4", features = ["full"] }

Quick Start

use metrics_lib::{init, metrics};

// Initialize once at startup
init();

// Counters
metrics().counter("requests").inc();
metrics().counter("errors").add(5);

// Gauges
metrics().gauge("cpu_usage").set(87.3);
metrics().gauge("memory_gb").add(1.5);

// Timers - automatic RAII timing
{
    let _timer = metrics().timer("api_call").start();
    // Your code here - automatically timed on drop
}

// Or time a closure
let result = metrics().time("db_query", || {
    // Database operation
    "user_data"
});

// System health monitoring
let cpu = metrics().system().cpu_used();
let memory_gb = metrics().system().mem_used_gb();

// Rate metering
metrics().rate("api_calls").tick();

Telemetry & Exporters (v0.9.3+)

Five built-in exporters render the current registry state to popular backends. All exporters share label and metadata support.

use metrics_lib::{init, metrics, LabelSet, Unit};
use metrics_lib::exporters::{prometheus, openmetrics};

init();

// One-time metric descriptions feed `# HELP` / `# TYPE` / `# UNIT` lines.
metrics().registry().describe_counter(
    "http_requests",
    "Total HTTP requests",
    Unit::Custom("1"),
);

// Labeled metrics — `(name, labels)` is the identity.
let labels = LabelSet::from([("method", "GET"), ("status", "200")]);
metrics().counter_with("http_requests", &labels).inc();

// Render the registry to Prometheus text format.
let body = prometheus::render(metrics().registry());
// Or OpenMetrics:
let body_om = openmetrics::render(metrics().registry());

End-to-end examples live in examples/: labels_demo, histogram_latency, prometheus_endpoint, statsd_push, otlp_push, snapshot_serde.

Observability Quick Start

• Integration Examples: see docs/API.md#integration-examples
• Grafana dashboard (ready to import): observability/grafana-dashboard.json
• Prometheus recording rules: observability/recording-rules.yaml
• Kubernetes Service: docs/k8s/service.yaml
• Prometheus Operator ServiceMonitor: docs/k8s/servicemonitor.yaml
• Secured ServiceMonitor (TLS/Bearer): docs/k8s/servicemonitor-secured.yaml

Commands

# Import Grafana dashboard via API
curl -X POST \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <GRAFANA_API_TOKEN>" \
  http://<grafana-host>/api/dashboards/db \
  -d @observability/grafana-dashboard.json

# Validate Prometheus recording rules
promtool check rules observability/recording-rules.yaml

# Apply Kubernetes manifests
kubectl apply -f docs/k8s/service.yaml
kubectl apply -f docs/k8s/servicemonitor.yaml
# For secured endpoints
kubectl apply -f docs/k8s/servicemonitor-secured.yaml

Advanced Usage

Async Support

use std::time::Duration;
use metrics_lib::{metrics, AsyncMetricBatch, AsyncTimerExt};

// Async timing with zero overhead and typed result
let result: &str = metrics()
    .timer("async_work")
    .time_async(|| async {
        tokio::time::sleep(Duration::from_millis(10)).await;
        "completed"
    })
    .await;

// Batched async updates (flush takes &MetricsCore)
let mut batch = AsyncMetricBatch::new();
batch.counter_inc("requests", 1);
batch.gauge_set("cpu", 85.2);
batch.flush(metrics());

Examples

Run these self-contained examples to see the library in action:

• Quick Start

  • File: examples/quick_start.rs
  • Run:

    cargo run --example quick_start --release
    

• Streaming Rate Window

  • File: examples/streaming_rate_window.rs
  • Run:

    cargo run --example streaming_rate_window --release
    

• Axum Registry Integration (minimal web service)

  • File: examples/axum_registry_integration.rs
  • Run:

    cargo run --example axum_registry_integration --release
    

  • Endpoints:
    • GET /health — liveness probe
    • GET /metrics-demo — updates metrics (counter/gauge/timer/rate)
    • GET /export — returns a JSON snapshot of selected metrics

• Quick Tour

  • File: examples/quick_tour.rs
  • Run:

    cargo run --example quick_tour --release
    

• Async Batch + Timing

  • File: examples/async_batch_timing.rs
  • Run:

    cargo run --example async_batch_timing --release
    

• Token Bucket Rate Limiter

  • File: examples/token_bucket_limiter.rs
  • Run:

    cargo run --example token_bucket_limiter --release
    

• Custom Exporter (OpenMetrics-like)

  • File: examples/custom_exporter_openmetrics.rs
  • Run:

    cargo run --example custom_exporter_openmetrics --release
    

• Axum Middleware Metrics (minimal)

  • File: examples/axum_middleware_metrics.rs
  • Run:

    cargo run --example axum_middleware_metrics --release
    

• Contention & Admission Demo

  • File: examples/contention_admission.rs
  • Run:

    cargo run --example contention_admission --release
    

• CPU Stats Overview

  • File: examples/cpu_stats.rs
  • Run:

    cargo run --example cpu_stats --release
    

• Memory Stats Overview

  • File: examples/memory_stats.rs
  • Run:

    cargo run --example memory_stats --release
    

• Health Dashboard

  • File: examples/health_dashboard.rs
  • Run:

    cargo run --example health_dashboard --release
    

• Cache Hit/Miss

  • File: examples/cache_hit_miss.rs
  • Run:

    cargo run --example cache_hit_miss --release
    

• Broker Throughput

  • File: examples/broker_throughput.rs
  • Run:

    cargo run --example broker_throughput --release
    

More Real-World Examples (API Reference)

• Building a Custom Exporter — see docs/API.md → Building a Custom Exporter
• Memory Stats: total/used/free + percentages — see docs/API.md → Memory Stats
• Memory % used for an operation (estimate) — see docs/API.md → Memory % for an operation
• CPU Stats: total/used/free + percentages — see docs/API.md → CPU Stats
• CPU % used for an operation (estimate) — see docs/API.md → CPU % for an operation

Resilience Features

Running many examples quickly

For convenience, a helper script runs a curated set of non-blocking examples sequentially in release mode (skips server examples like Axum middleware):

bash tools/run_examples.sh

You can also pass a custom comma-separated list via EXAMPLES:

EXAMPLES="quick_start,quick_tour,cpu_stats" bash tools/run_examples.sh

use metrics_lib::{AdaptiveSampler, SamplingStrategy, MetricCircuitBreaker};

// Adaptive sampling under load
let sampler = AdaptiveSampler::new(SamplingStrategy::Dynamic {
    min_rate: 1,
    max_rate: 100,
    target_throughput: 10000,
});

if sampler.should_sample() {
    metrics().timer("expensive_op").record(duration);
}

// Circuit breaker protection
let breaker = MetricCircuitBreaker::new(Default::default());
if breaker.is_allowed() {
    // Perform operation
    breaker.record_success();
} else {
    // Circuit is open, skip operation
}

System Monitoring

let health = metrics().system();

println!("CPU: {:.1}%", health.cpu_used());
println!("Memory: {:.1} GB", health.mem_used_gb());
println!("Load: {:.2}", health.load_avg());
println!("Threads: {}", health.thread_count());

Benchmarks

Run the included benchmarks to see performance on your system:

# Basic performance comparison
cargo run --example benchmark_comparison --release

# Comprehensive benchmarks (Criterion)
cargo bench --bench metrics_bench --features meter

# Cross-platform system tests
cargo test --all-features

Interpreting Criterion Results

• Criterion writes reports to target/criterion/ with per-benchmark statistics and comparisons.
• Key numbers to watch: time: [low … mean … high] and outlier percentages.
• Compare runs over time to detect regressions. Store artifacts from CI for historical comparison.
• Benchmarks are microbenchmarks; validate with end-to-end measurements as needed.

CI Artifacts

• Pull Requests: CI runs a fast smoke bench and uploads criterion-reports with target/criterion.
• Nightly: The Benchmarks workflow runs full-duration benches on Linux/macOS/Windows and uploads artifacts as benchmark-results-<os>.
• You can download these artifacts from the GitHub Actions run page to compare results across commits.

Latest CI Benchmarks

View the latest nightly results and artifacts here:

Latest CI Benchmarks (Benchmarks workflow)

Benchmark history (GitHub Pages):

Benchmark History (gh-pages)

Sample Results (latest local run; Windows x86_64, Rust stable):

Counter Increment: 1.48 ns/op (676.36 M ops/sec)
Gauge Set:         0.40 ns/op (2500.31 M ops/sec)
Timer Record:      3.17 ns/op (314.99 M ops/sec)
Mixed Operations:  151.58 ns/op (6.60 M ops/sec)

Notes: Latest numbers taken from local Criterion means under target/criterion/**/new/estimates.json. Actual throughput varies by CPU and environment; use the GitHub Pages benchmark history for trends.

Methodology

• Tooling: Criterion with release builds.
• Flags for stability on local runs: cargo bench --bench metrics_bench --features meter -- -w 3.0 -m 5.0 -n 100 (increase on dedicated runners).
• Environment disclosure (example):
  • CPU: Apple M1 Pro (performance cores)
  • Rust: stable toolchain
  • Target: aarch64-apple-darwin
  • Governor: default (for CI use a performance governor where applicable)

See also: docs/zero-overhead-proof.md for assembly inspection and binary size analysis, and docs/performance-tuning.md for environment hardening.

Architecture

Lock-Free Design

• Atomic Operations: All metrics use Relaxed ordering for maximum performance
• Cache-Line Alignment: 64-byte alignment eliminates false sharing
• Compare-and-Swap: Lock-free min/max tracking in timers
• Thread-Local Storage: Fast random number generation for sampling

Memory Layout

#[repr(align(64))]
pub struct Counter {
    value: AtomicU64,           // 8 bytes
    // 56 bytes padding to cache line boundary
}

Zero-Cost Abstractions

• RAII Timers: Compile-time guaranteed cleanup
• Async Guards: No allocation futures for timing
• Batch Operations: Vectorized updates for efficiency

Testing

Comprehensive automated coverage includes:

• default features: 63 unit tests + 2 API smoke tests + 14 rustdoc tests
• all features: 110 unit tests + 3 API smoke tests + 17 rustdoc tests

# Run all tests
cargo test

# Test with all features
cargo test --all-features

# Run only bench-gated tests (feature-flagged and ignored by default)
cargo test --features bench-tests -- --ignored

# Run benchmarks (Criterion)
cargo bench --bench metrics_bench --features meter

# Check for memory leaks (with valgrind)
cargo test --target x86_64-unknown-linux-gnu

Cross-Platform Support

Tier 1 Support:

• ✅ Linux (x86_64, aarch64)
• ✅ macOS (x86_64, Apple Silicon)
• ✅ Windows (x86_64)

System Integration:

• Linux: /proc filesystem, sysinfo APIs
• macOS: mach system calls, sysctl APIs
• Windows: Performance counters, WMI integration

Graceful Fallbacks:

• Unsupported platforms default to portable implementations
• Feature detection at runtime
• No panics on missing system features

Performance Notes

Latest local Criterion means (Windows x86_64, Rust stable, release build, held Arc<Counter> / Arc<Gauge> / Arc<Timer> handle — see Methodology above):

Calling metrics().counter("name") on every increment is slower than holding the Arc — the global lookup costs an RwLock read + HashMap hit

• Arc::clone(). Cache the handle in hot loops. A side-by-side bench (global_metrics group in cargo bench) shows the realistic global-lookup cost for comparison.

A populated head-to-head comparison against metrics-rs, prometheus, and statsd will ship with the v1.0.0 release once equivalent test fixtures are in place.

Configuration

Feature Flags

# All stable features:
metrics-lib = { version = "0.9.4", features = ["all"] }

# Full build including async and serde:
metrics-lib = { version = "0.9.4", features = ["full"] }

# Minimal build (counter only):
metrics-lib = { version = "0.9.4", features = ["minimal"] }

Runtime Configuration

use metrics_lib::{init_with_config, Config};

let config = Config {
    max_metrics: 10000,
    update_interval_ms: 1000,
    enable_system_metrics: true,
};

init_with_config(config);

Contributing

We welcome contributions! Please see our Contributing Guide.

Development Setup

# Clone repository
git clone https://github.com/jamesgober/metrics-lib.git
cd metrics-lib

# Run tests
cargo test --all-features

# Run benchmarks
cargo bench --bench metrics_bench --features meter

# Check formatting and lints
cargo fmt --all -- --check
cargo clippy --all-features -- -D warnings

Links

• 📚 Documentation
• 📦 Crates.io
• 🐛 Issues
• 💬 Discussions

Guides

• Migrating from metrics-rs: docs/migrating-from-metrics-rs.md
• Performance Tuning: docs/performance-tuning.md
• Zero-Overhead Proof: docs/zero-overhead-proof.md
• API Stability Guarantees: docs/api-stability.md