@pauloferreira25/aws-lambda-logger

Structured, console.log-based logger built for AWS Lambda — no worker threads, no transport machinery that doesn't survive a frozen execution environment. Correlation id propagation via AsyncLocalStorage, so every log line inside a request carries it automatically, with no need to thread it through every function call by hand.

Why not pino

pino's default transport (thread-stream) runs on a worker thread. That model fits a long-running server; it doesn't fit Lambda, where the execution environment can be frozen or torn down between invocations and CloudWatch already captures stdout directly. This package writes one JSON line per log call, synchronously, with no background thread.

Install

npm install @pauloferreira25/aws-lambda-logger

Usage

import { makeLogger, runWithCorrelationId } from '@pauloferreira25/aws-lambda-logger'

const log = makeLogger({ config: { level: 'debug' } })

export const handler = (event, context) =>
  runWithCorrelationId({
    correlationId: context.awsRequestId,
    run: async () => {
      log.debug({ context: { event }, message: 'handler' })
      // every log call inside this run — including ones made deep inside
      // repository/service functions built at module load time — carries
      // the same correlationId automatically.
    },
  })

OpenTelemetry trace correlation

Every log line automatically includes traceId and spanId when an OpenTelemetry span is active — no wiring required beyond having the application's own OTel setup in place (e.g. the AWS Distro for OpenTelemetry Lambda layer, or a manually configured SDK). This package only depends on @opentelemetry/api, the lightweight, side-effect-free API surface — it never registers a global tracer or context manager itself. If the application hasn't configured OpenTelemetry at all, traceId/spanId are simply omitted; nothing breaks.

correlationId and traceId/spanId serve different purposes and both can appear on the same line: correlationId identifies one Lambda invocation, traceId identifies a trace that may span multiple services.

API

• makeLogger({ config: { level } }) — returns a Log with debug, info, warn, error, each taking { context, message }. Calls below the configured level are silently dropped.
• runWithCorrelationId({ correlationId, run }) — runs run with correlationId bound for its entire async duration, including anything it awaits transitively. Concurrent calls never leak into each other.
• getCorrelationId() — reads the correlationId bound by the nearest enclosing runWithCorrelationId, or undefined if none is active.
• getOtelTraceContext() — reads { traceId, spanId } from the active OpenTelemetry span, or undefined if none is active or OpenTelemetry isn't configured.

License

Not yet decided — add a LICENSE file and the license field in package.json before publishing.