Running commands upon creation of instances using AWS Elastic Beanstalk

Question

I've been looking at various methods to run commands upon creation of EC2 instances using Elastic Beanstalk on AWS. I've been given different methods to do this through AWS Tech Support, including life cycle hooks, custom AMI's, and .ebextensions. I've been having issues getting the first 2 methods (life cycle hooks and custom AMIs) to work with EB.

I'm currently using .ebextensions to run commands upon deploy, but not sure if there's a way to run a set of commands upon creation only instead of every time I deploy code. For instance, I have a file .ebextensions/03-commands.config that contains the following code:

container_commands:
  01_npm_install:
    command: "npm install -g -f npm@latest"

However, I only want this code to run upon instance creation, not every time I deploy, as it currently does. Does anyone know a way to accomplish this?

Thanks in advance!

Answer 1

I would recommend creating an idempotent script in your application that leaves a marker file on the instance in some location say /var/myapp/marker using something like mkdir -p /var/myapp-state/; touch /var/myapp-state/marker on successful execution. That way in your script you can check that if the marker file exists you can make your script a no-op.

Then you can call your script from container commands but it will be a no-op everytime because on first successful execution it will create the marker file and subsequent executions will be no-ops.