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lambda-package-creation.md

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Lambda Package Creation Documentation

Overview

The create_lambda_package.sh script is responsible for creating the deployment package for the AWS Lambda function. This script automates the process of packaging the Python code and dependencies into a ZIP file that can be deployed to AWS Lambda.

Script Location

scripts/create_lambda_package.sh

Purpose

  • Creates a ZIP file containing the Lambda function code and dependencies
  • Calculates the SHA256 hash for Terraform's source code tracking
  • Excludes unnecessary files to keep the package size minimal
  • Ensures consistent packaging across different environments

How It Works

1. Package Creation Process

# Navigate to Lambda source directory
cd src/lambda

# Create ZIP file with all contents
zip -r ../../terraform/lambda_function.zip . -x "*.pyc" "__pycache__/*" "*.DS_Store"

2. Hash Calculation

The script calculates a SHA256 hash of the ZIP file for Terraform to track changes:

# macOS
SHA256_HASH=$(shasum -a 256 lambda_function.zip | cut -d' ' -f1 | base64)

# Linux
SHA256_HASH=$(sha256sum lambda_function.zip | cut -d' ' -f1 | base64)

3. File Structure

The resulting ZIP file contains:

lambda_function.zip
├── lambda_function.py    # Main Lambda handler
└── requirements.txt      # Python dependencies

Usage

Automated Usage (Recommended)

The script is automatically called during deployment:

./scripts/deploy.sh

Manual Usage

If you need to create the package manually:

# From project root
./scripts/create_lambda_package.sh

# Or using Makefile
make package

Output

The script outputs:

  • Package creation status
  • SHA256 hash for Terraform
  • Package size
  • File location

Example output:

Creating Lambda deployment package...
Zipping Lambda function...
Lambda package created: terraform/lambda_function.zip
SHA256 Hash: MTM5ZjIwZTlkOWE0NWU4YjA4MTk1MDhiOTc3MDkyNGI1MWM3OTNkNDc2YjU4N2JlOWRmZWU0ZjFiZDQ0ZTkyYgo=
Package size: 4.0K

Integration with Terraform

The Terraform configuration uses the generated package:

# In terraform/lambda.tf
locals {
  lambda_zip_path = "${path.module}/lambda_function.zip"
}

resource "aws_lambda_function" "todo_api" {
  filename         = local.lambda_zip_path
  source_code_hash = filebase64sha256(local.lambda_zip_path)
  # ... other configuration
}

Troubleshooting

Common Issues

  1. Permission Denied

    chmod +x scripts/create_lambda_package.sh

  2. ZIP Command Not Found

    • Ensure zip is installed on your system
    • On macOS: brew install zip
    • On Ubuntu: sudo apt-get install zip

  3. Hash Calculation Fails

    • The script automatically detects macOS vs Linux
    • Ensure shasum (macOS) or sha256sum (Linux) is available

Verification

To verify the package was created correctly:

# Check if file exists
ls -la terraform/lambda_function.zip

# View contents
unzip -l terraform/lambda_function.zip

# Verify hash
shasum -a 256 terraform/lambda_function.zip

Customization

Adding Dependencies

To include additional Python packages:

  1. Add to src/lambda/requirements.txt
  2. Install locally: pip install -r src/lambda/requirements.txt -t src/lambda/
  3. Run the package script

Excluding Files

To exclude additional file types, modify the zip command:

zip -r ../../terraform/lambda_function.zip . \
  -x "*.pyc" "__pycache__/*" "*.DS_Store" "*.log" "*.tmp"

Best Practices

  1. Keep it Minimal: Only include necessary files
  2. Version Control: Don't commit the ZIP file (it's in .gitignore)
  3. Consistent Environment: Use the same Python version as Lambda runtime
  4. Dependencies: Use requirements.txt for dependency management
  5. Testing: Verify the package works before deployment

Related Files

  • src/lambda/lambda_function.py - Main Lambda function code
  • src/lambda/requirements.txt - Python dependencies
  • terraform/lambda.tf - Terraform Lambda configuration
  • scripts/deploy.sh - Deployment script that calls this script
  • Makefile - Contains package target