Install Yarn and NodeJS on AWS Elastic Beanstalk EC2 Instance with Amazon Linux Ruby Platform, prior to precompiling assets for a Rails app

yarn.config

# vim: set ft=yaml:
# @see https://gist.github.com/sealocal/0cd468ba4f12cdada436aebe534b40da
---
files:
  '/opt/elasticbeanstalk/hooks/appdeploy/pre/09_yarn_install.sh':
    mode: '000775'
    owner: root
    group: users
    content: |
      #!/bin/bash

      EB_APP_STAGING_DIR=$(/opt/elasticbeanstalk/bin/get-config container -k app_staging_dir)
      EB_APP_USER=$(/opt/elasticbeanstalk/bin/get-config container -k app_user)

      if [[ $(which yarn 2>&1 > /dev/null) != 0 ]]; then
        # Consider that the EC2 instance is managed by AWS Elastic Beanstalk.
        # Changes made via SSH WILL BE LOST if the instance is replaced by auto-scaling.
        # QUESTION: Will this script be run on new instances that are created by auto-scaling?
        # QUESTION: Should installation be moved to a rake task?

        sudo wget https://dl.yarnpkg.com/rpm/yarn.repo -O /etc/yum.repos.d/yarn.repo
        file /etc/yum.repos.d/yarn.repo

        if [[ $(node --version) != 'v6.10.0' ]]; then
          # Download the Node v6 setup script
          curl --location https://rpm.nodesource.com/setup_6.x > /home/ec2-user/node_install.sh
          # Confirm that it downloaded
          file /home/ec2-user/node_install.sh
          # Run the Node v6 setup script
          sudo bash /home/ec2-user/node_install.sh
          # Install nodejs
          sudo yum install -y nodejs
          node --version
        fi

        # install yarn
        sudo yum install -y yarn
        yarn --version
      fi

      cd $EB_APP_STAGING_DIR
      yarn install
commands:
  01_remove_old_yarn_script:
    command: 'rm -f /opt/elasticbeanstalk/hooks/appdeploy/pre/*yarn*.bak'