OpenTelemetry (OTel)

Production standards for instrumenting applications to achieve high-fidelity observability.

1. Distributed Tracing

• Trace Context Propagation: Always propagate the traceparent and tracestate headers across HTTP and RPC boundaries (using W3C Trace Context).
• Span Granularity: Create spans for logical units of work. Avoid creating spans for every single function call (which causes overhead). Focus on:
  • Incoming HTTP requests
  • Database queries
  • External API/LLM calls
  • Background task executions
• Semantic Conventions: Use standardized span attributes (e.g., http.method, http.status_code, db.system). Do not invent custom attribute names when standard ones exist.

2. Span Implementation Guidelines

• Status and Errors: explicitly set the span status to Error when an exception occurs, and record the exception object on the span.
• Payloads: Avoid logging sensitive PII or massive payloads in span attributes. Log structural identifiers (e.g., user.id, tenant.id).

// Example: Creating a Span in Node.js
tracer.startActiveSpan('database.query', (span) => {
  try {
    span.setAttribute('db.statement', queryText)
    const result = db.execute(queryText)
    span.setStatus({ code: SpanStatusCode.OK })
    return result
  } catch (error) {
    span.recordException(error)
    span.setStatus({ code: SpanStatusCode.ERROR, message: error.message })
    throw error
  } finally {
    span.end()
  }
})

3. Metrics

• RED Metrics: Focus on Rate (requests/sec), Errors (error rate), and Duration (latency distribution).
• Histograms over Summaries: Use Histograms for latency measurements to allow accurate percentile aggregations across distributed instances.

4. Exporters and Infrastructure

• OTLP Exporters: Always export telemetry using the OpenTelemetry Protocol (OTLP) via gRPC or HTTP to an OpenTelemetry Collector, rather than exporting directly to backend vendors (Datadog, Honeycomb) from the application.
• Batching: Use batch span processors (BatchSpanProcessor) in production to minimize performance overhead. Only use SimpleSpanProcessor for local debugging.

5. Cloudflare Workers Integration

• Trace Exporters: When running on Cloudflare Workers, standard OTLP exporters may fail due to runtime constraints. Use @microlabs/otel-cf-workers or specifically tailored fetch-based HTTP exporters for compatibility.
• Context Preservation: Always wrap the Worker's fetch handler or Scheduled handler using the telemetry wrapper to ensure trace context flows correctly through the V8 isolate.

6. Structured Logging

• Correlated Logs: Ensure all log lines emit the current trace_id and span_id. This allows bridging between logs and traces.
• JSON Format: Output logs in JSON format in production. Avoid unstructured string logging.