Opentelemetry Rust

OpenTelemetry Rust Instrumentation

Expert guidance for instrumenting Rust applications with OpenTelemetry using the official Rust SDK and manual instrumentation.

Quick Start

Install Dependencies

Add to your Cargo.toml:

[dependencies]
opentelemetry = "0.27"
opentelemetry-sdk = "0.27"
opentelemetry-otlp = "0.27"
tokio = { version = "1", features = ["full"] }

Initialize OpenTelemetry

use opentelemetry::{global, KeyValue};
use opentelemetry_sdk::Resource;
use opentelemetry_sdk::trace::SdkTracerProvider;
use opentelemetry_otlp::{SpanExporter, WithExportConfig};

fn init_tracer() -> SdkTracerProvider {
    let exporter = SpanExporter::builder()
        .with_http()
        .build()
        .expect("Failed to create exporter");
    
    let provider = SdkTracerProvider::builder()
        .with_batch_exporter(exporter)
        .with_resource(Resource::builder()
            .with_service_name("my-service")
            .build())
        .build();
    
    global::set_tracer_provider(provider.clone());
    provider
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let tracer_provider = init_tracer();
    
    // Your application code here
    
    tracer_provider.shutdown()?;
    Ok(())
}

Core Instrumentation Patterns

Creating Spans

use opentelemetry::{
    global,
    trace::{TraceContextExt, Tracer},
    KeyValue,
};

fn process_request(user_id: &str) -> Result<(), Box<dyn std::error::Error>> {
    let tracer = global::tracer("my-service");
    
    tracer.in_span("process-request", |cx| {
        let span = cx.span();
        span.set_attribute(KeyValue::new("user.id", user_id.to_string()));
        
        // Do work
        match do_work() {
            Ok(_) => {
                span.set_attribute(KeyValue::new("result", "success"));
                Ok(())
            }
            Err(e) => {
                span.record_error(&e);
                Err(e)
            }
        }
    })
}

Manual Span Creation and Management

use opentelemetry::trace::{Span, Status, Tracer};

fn manual_span_example() {
    let tracer = global::tracer("my-service");
    let mut span = tracer.start("manual-span");
    
    span.set_attribute(KeyValue::new("custom.attribute", "value"));
    
    // Do work
    
    span.set_status(Status::Ok);
    span.end();
}

Context Propagation

use opentelemetry::Context;

fn parent_operation() {
    let tracer = global::tracer("my-service");
    
    tracer.in_span("parent", |parent_cx| {
        // Context automatically propagates to child
        child_operation(parent_cx);
    });
}

fn child_operation(cx: &Context) {
    let tracer = global::tracer("my-service");
    let _child_span = tracer.start_with_context("child", cx);
    
    // Do work
}

HTTP Instrumentation

HTTP Server (with Axum)

use axum::{Router, routing::get};
use tower_http::trace::TraceLayer;

async fn handler() -> &'static str {
    "Hello, World!"
}

#[tokio::main]
async fn main() {
    let app = Router::new()
        .route("/", get(handler))
        .layer(TraceLayer::new_for_http());
    
    let listener = tokio::net::TcpListener::bind("0.0.0.0:3000")
        .await
        .unwrap();
    axum::serve(listener, app).await.unwrap();
}

HTTP Client (with reqwest)

For HTTP clients, you'll need to manually propagate context:

use opentelemetry::global;
use opentelemetry::trace::{TraceContextExt, Tracer};
use opentelemetry_http::HeaderInjector;
use reqwest::Client;

async fn make_request(url: &str) -> Result<String, Box<dyn std::error::Error>> {
    let tracer = global::tracer("my-service");
    
    tracer.in_span("http-request", |cx| async move {
        let mut headers = reqwest::header::HeaderMap::new();
        
        // Inject trace context into headers
        global::get_text_map_propagator(|propagator| {
            propagator.inject_context(&cx, &mut HeaderInjector(&mut headers));
        });
        
        let client = Client::new();
        let response = client.get(url)
            .headers(headers)
            .send()
            .await?;
        
        response.text().await
    }).await
}

Integration with Tracing Crate

The tracing crate is the recommended approach for logging and structured diagnostics in Rust. OpenTelemetry integrates seamlessly with it:

Setup with Tracing

[dependencies]
tracing = "0.1"
tracing-subscriber = "0.3"
opentelemetry-appender-tracing = "0.27"

use opentelemetry_appender_tracing::layer::OpenTelemetryTracingBridge;
use opentelemetry_sdk::logs::SdkLoggerProvider;
use tracing_subscriber::prelude::*;
use tracing::{info, error};

fn init_logs() -> SdkLoggerProvider {
    let exporter = opentelemetry_otlp::LogExporter::builder()
        .with_http()
        .build()
        .expect("Failed to create log exporter");
    
    let provider = SdkLoggerProvider::builder()
        .with_batch_exporter(exporter)
        .with_resource(Resource::builder()
            .with_service_name("my-service")
            .build())
        .build();
    
    let layer = OpenTelemetryTracingBridge::new(&provider);
    tracing_subscriber::registry().with(layer).init();
    
    provider
}

fn main() {
    let logger_provider = init_logs();
    
    info!("Application started");
    error!(error.kind = "database", "Connection failed");
    
    logger_provider.shutdown().expect("Failed to shutdown logger");
}

Metrics

Creating Metrics

use opentelemetry::{global, KeyValue};
use opentelemetry::metrics::Counter;

fn setup_metrics() {
    let meter = global::meter("my-service");
    
    // Counter
    let counter = meter
        .u64_counter("http.requests")
        .with_description("Total HTTP requests")
        .build();
    
    counter.add(1, &[
        KeyValue::new("http.method", "GET"),
        KeyValue::new("http.status", 200),
    ]);
    
    // Histogram
    let histogram = meter
        .f64_histogram("http.request.duration")
        .with_unit("ms")
        .with_description("HTTP request duration")
        .build();
    
    histogram.record(150.5, &[
        KeyValue::new("http.method", "GET"),
    ]);
    
    // UpDownCounter
    let active_connections = meter
        .i64_up_down_counter("http.active_connections")
        .with_description("Number of active connections")
        .build();
    
    active_connections.add(1, &[]);  // Connection opened
    active_connections.add(-1, &[]); // Connection closed
}

Async/Observable Metrics

use opentelemetry::metrics::ObservableGauge;
use std::sync::Arc;
use std::sync::atomic::{AtomicU64, Ordering};

fn setup_async_metrics() {
    let meter = global::meter("my-service");
    let memory_usage = Arc::new(AtomicU64::new(0));
    let memory_usage_clone = memory_usage.clone();
    
    let _gauge = meter
        .u64_observable_gauge("process.memory.usage")
        .with_description("Current memory usage")
        .with_unit("bytes")
        .with_callback(move |observer| {
            let value = memory_usage_clone.load(Ordering::Relaxed);
            observer.observe(value, &[]);
        })
        .build();
}

Complete Initialization

Initializing All Signals

use opentelemetry::{global, KeyValue};
use opentelemetry_sdk::{
    logs::SdkLoggerProvider,
    metrics::SdkMeterProvider,
    trace::SdkTracerProvider,
    Resource,
};
use opentelemetry_otlp::{LogExporter, MetricExporter, SpanExporter, WithExportConfig};
use std::sync::OnceLock;

fn get_resource() -> Resource {
    static RESOURCE: OnceLock<Resource> = OnceLock::new();
    RESOURCE
        .get_or_init(|| {
            Resource::builder()
                .with_service_name("my-service")
                .with_service_version("1.0.0")
                .build()
        })
        .clone()
}

fn init_traces() -> SdkTracerProvider {
    let exporter = SpanExporter::builder()
        .with_http()
        .build()
        .expect("Failed to create trace exporter");
    
    SdkTracerProvider::builder()
        .with_batch_exporter(exporter)
        .with_resource(get_resource())
        .build()
}

fn init_metrics() -> SdkMeterProvider {
    let exporter = MetricExporter::builder()
        .with_http()
        .build()
        .expect("Failed to create metric exporter");
    
    SdkMeterProvider::builder()
        .with_periodic_exporter(exporter)
        .with_resource(get_resource())
        .build()
}

fn init_logs() -> SdkLoggerProvider {
    let exporter = LogExporter::builder()
        .with_http()
        .build()
        .expect("Failed to create log exporter");
    
    SdkLoggerProvider::builder()
        .with_batch_exporter(exporter)
        .with_resource(get_resource())
        .build()
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let tracer_provider = init_traces();
    global::set_tracer_provider(tracer_provider.clone());
    
    let meter_provider = init_metrics();
    global::set_meter_provider(meter_provider.clone());
    
    let logger_provider = init_logs();
    
    // Your application code here
    
    // Shutdown all providers
    tracer_provider.shutdown()?;
    meter_provider.shutdown()?;
    logger_provider.shutdown()?;
    
    Ok(())
}

Sampling

Probability Sampler

use opentelemetry_sdk::trace::{Sampler, SamplerResult};

let provider = SdkTracerProvider::builder()
    .with_sampler(Sampler::TraceIdRatioBased(0.1)) // Sample 10%
    .with_batch_exporter(exporter)
    .with_resource(get_resource())
    .build();

Parent-Based Sampler

let provider = SdkTracerProvider::builder()
    .with_sampler(Sampler::ParentBased(Box::new(
        Sampler::TraceIdRatioBased(0.1)
    )))
    .with_batch_exporter(exporter)
    .with_resource(get_resource())
    .build();

Async Runtime Integration

OpenTelemetry Rust works seamlessly with Tokio and other async runtimes:

use tokio::task;

async fn async_operation() {
    let tracer = global::tracer("my-service");
    
    tracer.in_span("async-parent", |cx| async move {
        // Spawn async task with context
        let handle = task::spawn(async move {
            let tracer = global::tracer("my-service");
            tracer.in_span("async-child", |_cx| async move {
                // Do async work
            }).await;
        });
        
        handle.await.unwrap();
    }).await;
}

Best Practices

1. Use the global providers - Set global tracer/meter providers for easy access
2. Always shutdown - Call shutdown() on all providers before application exit
3. Use batch exporters - Batch exporters provide better performance than simple exporters
4. Resource attributes - Always set service.name and other identifying attributes
5. Integrate with tracing - Use the tracing crate for structured logging
6. Context propagation - Use in_span for automatic context management
7. Error handling - Use span.record_error() to capture errors
8. Semantic conventions - Follow OpenTelemetry semantic conventions for attribute names
9. Lazy initialization - Use OnceLock or Lazy for resource initialization
10. Async-aware - Ensure context propagation works correctly with async/await

Advanced Topics

For detailed examples covering HTTP services, database instrumentation, microservices patterns, and complex scenarios, see references/examples.md.

Troubleshooting

Spans not appearing

• Verify exporter endpoint is accessible
• Check that shutdown() is called on tracer provider
• Ensure global tracer provider is set
• Check batch exporter timeout settings

Context not propagating

• Use in_span for automatic context management
• Pass context explicitly when needed
• Verify async context propagation with task::spawn

Performance issues

• Use batch exporters instead of simple exporters
• Adjust batch size and timeout settings
• Implement appropriate sampling
• Consider using AlwaysOff sampler for high-throughput scenarios

Compilation errors

• Ensure compatible versions of OpenTelemetry crates
• Check minimum Rust version (1.75+)
• Verify all required features are enabled

Key Dependencies

• opentelemetry - Core API
• opentelemetry-sdk - SDK implementation
• opentelemetry-otlp - OTLP exporter (HTTP and gRPC)
• opentelemetry-stdout - Stdout exporter for development
• opentelemetry-appender-tracing - Integration with tracing crate
• opentelemetry-semantic-conventions - Semantic conventions
• opentelemetry-http - HTTP utilities for propagation

Framework Integrations

• Axum: Use tower-http with TraceLayer
• Actix-web: Community instrumentation available
• Rocket: Manual instrumentation recommended
• Tonic (gRPC): Interceptor-based instrumentation

Resources

• OpenTelemetry Rust Docs
• OpenTelemetry Rust GitHub
• OpenTelemetry Rust Examples
• Tracing Crate

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