OpenTelemetry

OpenTelemetry is a vendor-neutral observability framework for generating, collecting, and exporting traces, metrics, and logs.

Documentation

• Docs: https://opentelemetry.io/docs/languages/js/

Key Capabilities

OpenTelemetry JS bundles capabilities that developers often reach for separate tools to cover:

• Auto-instrumentation: @opentelemetry/auto-instrumentations-node automatically instruments popular frameworks and libraries (Express, HTTP, gRPC, database clients) with zero code changes — no manual span creation needed for common libraries
• Resource detection: built-in detectors for cloud providers, containers, and process info via OTEL_NODE_RESOURCE_DETECTORS — no need for custom resource-tagging middleware
• Context propagation: W3C TraceContext and Baggage propagated automatically across async boundaries when using tracer.startActiveSpan — no manual context threading required

Best Practices

• Instrumentation must load before application code — For ESM projects, use node --import ./instrumentation.mjs. For CommonJS projects or the zero-code package (@opentelemetry/auto-instrumentations-node), use node --require @opentelemetry/auto-instrumentations-node/register (or --require ./instrumentation.js). Loading instrumentation after app code silently produces no-op spans with no errors thrown.
• Use BatchSpanProcessor in production, never SimpleSpanProcessor — the simple processor exports synchronously on every span end, adding latency to every request. BatchSpanProcessor is the correct choice for production; SimpleSpanProcessor is only appropriate for debugging.
• SDK initialization failure is silent — if the SDK is initialized too late or fails to initialize, OpenTelemetry returns no-op implementations and emits no errors. Always verify spans appear in your exporter before deploying.
• Always call span.end() — spans that are never ended are never exported. Wrap span bodies in try/finally to guarantee span.end() is called even on exceptions.
• Lower the default sample rate for production — the getting-started default captures 100% of traces. Set OTEL_TRACES_SAMPLER=parentbased_traceidratio and OTEL_TRACES_SAMPLER_ARG=0.1 (or equivalent SDK config) before going to production to avoid excessive collector and backend costs.