Bin Scripts (Build, Deploy, & More)

Lamby will install a few bash scripts during the install task.

$ ./bin/rake -r lamby lamby:install

Essentially these are wrappers sam build and sam deploy CLI commands. Please read the AWS SAM CLI Command Reference for full details on what SAM can do. Details of our wrappers and potential hot spots (⚠️) are below.

Lastly, think of these scripts as starting points! You should add to or adjust each to meet your needs. Well maintained build and deploy scripts will help you maintain good CI/CD practices no matter if they are used from your personal machine or in a more mature system like AWS CodePipeline.


This makes use of the sam build command along with the --use-container option to ensure gems with native extensions are built for AWS' Linux platform. A short description of each section:

  1. Sets up a pristine build environment.
  2. The SAM build. Uses lambci/docker-lambda containers.
  3. [HOOK] Section for Environments & Configuration options.
  4. [HOOK] Section for Asset Hosts & Precompiling options.
  5. Clean unneeded build artifacts like vendor gems & other un-needed files. Limits.
set -e

# Clean any previous bundle/builds.
rm -rf ./.aws-sam/build

# Ensure native extensions built for platform.
sam build --use-container

# [HOOK] Environments & Configuration

# [HOOK] Asset Hosts & Precompiling

# Clean un-needed artifacts.
pushd ./.aws-sam/build/RailsFunction/
rm -rf .aws-sam \
  .git \
  log \
  test \

⚠️ Does your Gemfile have private gems on GitHub?

If so, the SAM containerized build will have auth issues accessing them. One solution we like requires adding this line prior to the sam build command.

bundle config --local GITHUB__COM "$(git config github.token):x-oauth-basic"

It sets a Bundler config so the container can use your personal GitHub OAuth token. Make sure to set that up using this GitHub help article. Lastly, add this line to your Gemfile and switch all private gems to use this github source via HTTPS vs the git protocol. Most newer Rails Gemfiles do this already.

git_source(:github) { |repo| "{repo}.git" }

⚠️ Git Bundled Gems & Large Packages Sizes?

Using gems from Git sources can easily increase your Lambda's package size which is limited to 250MB. We recommend cleaning gem's .git directories from within the build's vendor/bundle directory. Add this prior to the last popd in the build script.

find vendor/bundle/ruby/2.5.0 \
  -type d \
  -name ".git" \
  -mindepth 2 \
  -maxdepth 2 \
  -exec rm -rf {} \;


Uses both the sam package and sam deploy commands to create or update your Lambda's CloudFormation stack in AWS. During the Lamby install, we will personalize this script and change any occurrence of APPNAMEHERE to the name of your Rails application.

set -e

export RAILS_ENV=${RAILS_ENV:="production"}
export CLOUDFORMATION_BUCKET=${CLOUDFORMATION_BUCKET:="lamby.cloudformation.$(whoami)"}


sam package \
  --region ${AWS_DEFAULT_REGION} \
  --template-file ./.aws-sam/build/template.yaml \
  --output-template-file ./.aws-sam/build/packaged.yaml \
  --s3-prefix "APPNAMEHERE-${RAILS_ENV}"

sam deploy \
  --template-file ./.aws-sam/build/packaged.yaml \
  --capabilities "CAPABILITY_IAM" \
  --parameter-overrides \

⚠️ CloudFormation Bucket

Your Lambda code needs to be packaged and uploaded to an S3 bucket prior to being deployed. Typically this single bucket is used for all your application stacks and is organized into "subdirectories" using the --s3-prefix option. It is a great idea for you to change this to something that makes sense for you! If you have the AWS CLI installed, creating a bucket is a simple command like so. You can then use this as the default value for the CLOUDFORMATION_BUCKET above in all your deploy scripts.

$ aws s3 mb

⚠️ Deploying to Multiple Environments?

Feel free to make more per-environment deploy scripts. For example bin/deploy-staging may look like this. The AWS_PROFILE is an useful environment variable that helps you manage different AWS accounts via all CLI tools. Learn more about AWS Environment Variables.

set -e
export RAILS_ENV="staging"
export AWS_PROFILE="staging"
Lamby 🆕 Application Load Balancer ALB Support     GitHub