Script to AWS Lambda?

Question

I have this bash script which lists all active EC2 instances across regions:

for region in `aws ec2 describe-regions --output text | cut -f3` do
 echo -e "\nListing Instances in region:'$region'..."
 aws ec2 describe-instances --region $region
done

I'd like to port this to a Lambda function on AWS. What would be the best approach today? Do I have to use a wrapper or similar? Node? I googled and found what looked like mostly workarounds.. but they were a couple of years old. Would appreciate an up-to-date indication.

• Mark B: This is such a tiny and simple piece of code it would probably be quicker to just rewrite it as a Python Lambda function instead of trying to get bash working in Lambda.

Answer 1

Two ways to do it:

1. Using custom runtimes and layers: https://github.com/gkrizek/bash-lambda-layer

2. 'Exec'ing from another runtime: https://github.com/alestic/lambdash

Answer 2

You should write it in a language that has an AWS SDK, such as Python.

You should also think about what the Lambda function should do with the output, since at the moment it just retrieves information but doesn't do anything with it.

Here's a sample AWS Lambda function:

import boto3
def lambda_handler(event, context):
 instance_ids = []
 # Get a list of regions 
 ec2_client = boto3.client('ec2')
 response = ec2_client.describe_regions()
 # For each region
 for region in response['Regions']:
 # Get a list of instances
 ec2_resource = boto3.resource('ec2', region_name=region['RegionName'])
 for instance in ec2_resource.instances.all():
 instance_ids.append(instance.id)
 # Return the list of instance_ids
 return instance_ids

Please note that it takes quite a bit of time to call all the regions sequentially. The above can take 15-20 seconds.