OpenTelemetry

CNCF vendor-neutral standard for generating and exporting telemetry. Instrument once, route anywhere.

Three Signals

• Traces — a request’s path across services as a tree of spans (timing, attributes, status).
• Metrics — counters, gauges, histograms.
• Logs — correlated to traces via trace/span IDs.

Architecture

flowchart LR
  A[App + OTel SDK] -->|OTLP| C[OTel Collector]
  C --> J[Tracing backend: Jaeger / X-Ray / Tempo]
  C --> P[Metrics: Prometheus]
  C --> L[Logs backend]

• API + SDK — API is stable; SDK does sampling, batching, export.
• Instrumentation — auto (HTTP, DB, frameworks) vs manual (custom spans for business logic).
• Collector — receive → process (batch, filter, enrich) → export. Swap vendors without re-instrumenting.
• OTLP — the wire protocol. Exporters: Jaeger, Prometheus, AWS X-Ray (via ADOT), Datadog, …
• Context propagation — W3C traceparent header stitches spans across process boundaries.
• Semantic conventions — standard attribute names (http.request.method, db.system).

Node.js zero-code instrumentation

npm i @opentelemetry/api @opentelemetry/auto-instrumentations-node
 
# Local check: print spans to stdout
OTEL_SERVICE_NAME=my-svc OTEL_TRACES_EXPORTER=console \
OTEL_METRICS_EXPORTER=none OTEL_LOGS_EXPORTER=none \
node --require @opentelemetry/auto-instrumentations-node/register app.js
 
# Real backend: OTLP to a collector
OTEL_SERVICE_NAME=my-svc OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318 \
node --require @opentelemetry/auto-instrumentations-node/register app.js

Inbound http and outbound fetch/undici calls appear as spans with no code changes. Exporter batches flush on a timer (OTEL_BSP_SCHEDULE_DELAY, default 5000 ms) and on SIGTERM; process.exit() skips the flush.

Pairs with Prometheus for metrics; feeds the four golden signals in the Production Readiness Checklist.