Interlude: Getting Your Machine Ready

Before You Begin: Setup Checklist

Before we dive into building Lambda functions, make sure your local environment is ready to run Dockerized Ruby code.

You'll need the following tools installed:

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🐳 1. Docker

Docker lets you run containers locally, which is how we'll package and test your Lambda functions.

• Install Docker Desktop:
  https://www.docker.com/products/docker-desktop/
• After installation, run this command in your terminal to verify:

docker --version
# Example output: Docker version 24.0.2, build cb74dfc

If that works, you're good.

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🧰 2. Ruby + Bundler (Locally)

You'll want to be able to test and write Ruby code outside of Docker, too.

• Install Ruby (preferably 3.x)
  • If you're on macOS and use Homebrew:

    brew install ruby

  • Or use a Ruby version manager like rbenv or asdf
• Then install Bundler:

  gem install bundler

Check it with:

ruby -v
# ruby 3.2.x

bundle -v
# Bundler version 2.x

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🧪 3. Optional: Docker Compose (For Local Dev)

Docker Compose lets you run multiple containers or test environments with one file.

Most Docker Desktop installations already include docker-compose. Check with:

docker-compose --version
# or
docker compose version

If you see a version number, you're set.

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🗂 4. Directory Setup

Create a directory for your Lambda function. For example:

mkdir my_lambda_function
cd my_lambda_function

You'll be copying files like function.rb, Dockerfile, and Gemfile into this directory.

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With this setup, you'll be able to:

• Build your Docker image
• Run it locally
• Push it to AWS later

Once these steps are done, feel free to jump right into the rest of Chapter 3.