AWS Lambda Logging Layer with CDK (TypeScript)

This project demonstrates how to build and deploy a reusable logging layer for AWS Lambda using TypeScript, AWS CDK, and Node.js Lambda Layers. It includes two Lambda functions (createBlog, getBlogs) that use the shared logging logic via a Lambda Layer.

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🔧 Features

• Reusable Lambda Layer for logging and error tracking
• Higher-order function wrapper (withLogger) for structured logs
• Type-safe using AWS Lambda types (APIGatewayProxyEvent, etc.)
• CDK-defined infrastructure (Lambdas, Layer, API Gateway)
• Clean, scalable project structure

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📁 Project Structure

.
├── bin/                            # CDK app entry point
│   └── aws-lambda-layer-logger.ts
├── stacks/                         # CDK Stack
│   └── aws-lambda-layer-logger-stack.ts
├── src/
│   ├── lambdas/                    # Lambda functions
│   │   ├── createBlog.ts
│   │   └── getBlogs.ts
│   └── layers/
│       └── logger/                 # Shared logging Layer
│           ├── logger.ts
│           ├── withLogger.ts
│           ├── package.json
│           └── tsconfig.json
├── package.json
├── tsconfig.json
└── cdk.json

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🚀 Usage

1. Install dependencies

npm install

2. Build the logging layer (from src/layers/logger/)

cd src/layers/logger
npm install     # If using dependencies
npm run build   # Compile TypeScript to JS (outputs to dist/)

3. Deploy the stack

# Run this in the root project directory
cdk deploy

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✨ Example: Logging Wrapper

export const withLogging = (handler) => async (event, context) => {
  logger.info("Lambda Invoked", { ... });
  try {
    const result = await handler(event, context);
    logger.info("Lambda Succeeded", { statusCode: result.statusCode });
    return result;
  } catch (error) {
    logger.error("Lambda Failed", { error });
    throw error;
  }
};

Use it in your handler like:

export const handler = withLogging(async (event) => { ... });

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🧪 Endpoints

Method	Path	Lambda	Description
GET	/blog	getBlogs	Returns a list of blogs
POST	/blog	createBlog	Creates a new blog entry

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📖 Logs in CloudWatch

Structured logs include context:

{
  "level": "info",
  "msg": "Lambda Invoked",
  "requestId": "abc-123",
  "functionName": "CreateBlogFunction",
  "path": "/blog",
  "httpMethod": "POST"
}

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🧠 Why Use a Lambda Layer for Logging?

• Centralized, DRY logging logic
• Consistent structure across all functions
• Easier debugging and log querying
• Cleaner business logic in handlers