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

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

I actually ended up writing a script in Python because I feel more comfortable in Python then Bash,

#!/usr/bin/env python

"""
ec2-autoscale-instance.py

Read Autoscale DNS from AWS

Sample config file,
{
    "access_key": "key",
    "secret_key": "key",
    "group_name": "groupName"
}
"""

from __future__ import print_function
import argparse
import boto.ec2.autoscale
try:
    import simplejson as json
except ImportError:
    import json

CONFIG_ACCESS_KEY = 'access_key'
CONFIG_SECRET_KEY = 'secret_key'
CONFIG_GROUP_NAME = 'group_name'


def main():
    arg_parser = argparse.ArgumentParser(description=
                                         'Read Autoscale DNS names from AWS')
    arg_parser.add_argument('-c', dest='config_file',
                            help='JSON configuration file containing ' +
                                 'access_key, secret_key, and group_name')
    args = arg_parser.parse_args()
    config = json.loads(open(args.config_file).read())
    access_key = config[CONFIG_ACCESS_KEY]
    secret_key = config[CONFIG_SECRET_KEY]
    group_name = config[CONFIG_GROUP_NAME]

    ec2_conn = boto.connect_ec2(access_key, secret_key)
    as_conn = boto.connect_autoscale(access_key, secret_key)

    try:
        group = as_conn.get_all_groups([group_name])[0]
        instances_ids = [i.instance_id for i in group.instances]
        reservations = ec2_conn.get_all_reservations(instances_ids)
        instances = [i for r in reservations for i in r.instances]
        dns_names = [i.public_dns_name for i in instances]
        print('\n'.join(dns_names))
    finally:
        ec2_conn.close()
        as_conn.close()


if __name__ == '__main__':
    main()

Gist

The answer at https://stackoverflow.com/a/12592543/20774 was helpful in developing this script.

Answer 3

You can use the describe-auto-scaling-instances cli command, and query for your autoscale group name.

Example:

aws autoscaling describe-auto-scaling-instances --region us-east-1 --query 'AutoScalingInstances[?AutoScalingGroupName==`YOUR_ASG`]' --output text

Hope that helps

Answer 4

You can also use below command to fetch private ip address without any jq/awk/sed/cut

$ aws autoscaling describe-auto-scaling-instances --region us-east-1 --output text \
--query "AutoScalingInstances[?AutoScalingGroupName=='ASG-GROUP-NAME'].InstanceId" \
| xargs -n1 aws ec2 describe-instances --instance-ids $ID --region us-east-1 \
--query "Reservations[].Instances[].PrivateIpAddress" --output text

courtesy this

Answer 5

for ruby using aws-sdk gem v2 First create ec2 object as this:

ec2 = Aws::EC2::Resource.new(region: 'region', credentials: Aws::Credentials.new('IAM_KEY', 'IAM_SECRET') )

instances = []

ec2.instances.each do |i|
   p "instance id---", i.id
   instances << i.id

end

This will fetch all instance ids in particular region and can use more filters like ip_address.

Answer 6

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.