logging-setup

Lambda Logger Setup & Best Practices

Overview

Lambda observability requires structured logging, distributed tracing, and metrics. AWS Lambda Powertools provides a unified approach for TypeScript. Powertools 2.31+ adds event handler tracer middleware for HTTP routes and improved Parameters error handling.

Dependencies

pnpm add @aws-lambda-powertools/logger @aws-lambda-powertools/tracer @aws-lambda-powertools/metrics

Logger Setup

Configuration

// src/shared/logger/index.ts

import { Logger } from "@aws-lambda-powertools/logger";

export const logger = new Logger({
  serviceName: process.env.SERVICE_NAME ?? "real-estate-api",
  logLevel: (process.env.LOG_LEVEL as "DEBUG" | "INFO" | "WARN" | "ERROR") ?? "INFO",
  persistentLogAttributes: {
    environment: process.env.ENVIRONMENT ?? "development",
    version: process.env.VERSION ?? "unknown",
    // Multi-tenant real estate: set tenantId per request via logger.appendKeys({ tenantId })
    ...(process.env.TENANT_ID && { tenantId: process.env.TENANT_ID }),
  },
});

// Re-export for convenience
export type { Logger } from "@aws-lambda-powertools/logger";

Usage in Handlers

// src/functions/create-listing/handler.ts

import type { APIGatewayProxyHandler } from "aws-lambda";
import { logger } from "@/shared/logger";

export const handler: APIGatewayProxyHandler = async (event, context) => {
  // Add Lambda context to all logs
  logger.addContext(context);

  // Add request-specific context (tenantId from auth for multi-tenant real estate)
  logger.appendKeys({
    correlationId: event.headers["x-correlation-id"],
    path: event.path,
    method: event.httpMethod,
    ...(event.requestContext?.authorizer?.claims?.sub && {
      tenantId: event.requestContext.authorizer.claims["custom:tenantId"],
    }),
  });

  logger.info("Processing create listing request");

  try {
    const body = JSON.parse(event.body ?? "{}");

    logger.debug({ body }, "Request body parsed");

    const result = await listingService.create(body);

    if (!result.success) {
      logger.warn({ error: result.error }, "Listing creation failed");
      return { statusCode: 400, body: JSON.stringify(result.error) };
    }

    logger.info({ listingId: result.data.id }, "Listing created successfully");

    return { statusCode: 201, body: JSON.stringify(result.data) };
  } catch (error) {
    logger.error({ err: error }, "Unexpected error in create listing handler");
    throw error;
  }
};