Getting a list of instances in an EC2 auto scale group?

Question

Is there a utility or script available to retrieve a list of all instances from AWS EC2 auto scale group?

I need a dynamically generated list of production instance to hook into our deploy process. Is there an existing tool or is this something I am going to have to script?

Answer 1

Here is a bash command that will give you the list of IP addresses of your instances in an AutoScaling group.

for ID in $(aws autoscaling describe-auto-scaling-instances --region us-east-1 --query AutoScalingInstances[].InstanceId --output text);
do
aws ec2 describe-instances --instance-ids $ID --region us-east-1 --query Reservations[].Instances[].PublicIpAddress --output text
done

(you might want to adjust the region and to filter per AutoScaling group if you have several of them)

On a higher level point of view - I would question the need to connect to individual instances in an AutoScaling Group. The dynamic nature of AutoScaling would encourage you to fully automate your deployment and admin processes. To quote an AWS customer : "If you need to ssh to your instance, change your deployment process"

--Seb

Answer 2

The describe-auto-scaling-groups command from the AWS Command Line Interface looks like what you're looking for.

Edit: Once you have the instance IDs, you can use the describe-instances command to fetch additional details, including the public DNS names and IP addresses.