This script lists the Auto Scaling groups in an AWS account that have the "eks:cluster-name" tag matching the specified value, along with the number of instances in each group and the oldest launch time of those instances.

asg_view.sh

#!/bin/bash

# Filename: asg_view.sh
#
# Description: This script lists the Auto Scaling groups in an AWS account that have the "eks:cluster-name" tag 
#              matching the specified value, along with the number of instances in each group and the oldest 
#              launch time of those instances. It uses the AWS CLI to query the necessary information.
#
# Usage: ./asg_view.sh   <cluster_name>   <region>   <profile>
#
# Parameters:
#   <cluster_name> - The value of the "eks:cluster-name" tag to filter Auto Scaling groups by.
#   <region> - The AWS region to run the AWS CLI commands in.
#   <profile> - The AWS CLI profile to use for authentication.

cluster_name=$1
region=$2
profile=$3

export AWS_DEFAULT_REGION=$region
export AWS_PROFILE=$profile

# Get the list of Auto Scaling groups with the "eks:cluster-name" tag
asg_list=$(aws autoscaling describe-auto-scaling-groups --query "AutoScalingGroups[?contains(Tags[?Key=='eks:cluster-name'].Value, '$cluster_name')].AutoScalingGroupName" --output text)

for asg_name in $asg_list; do
  # Get the instance IDs of the instances in the Auto Scaling group
  instance_ids=$(aws autoscaling describe-auto-scaling-groups --auto-scaling-group-names $asg_name --query 'AutoScalingGroups[].Instances[].InstanceId' --output text)

  # Get the launch time of the instances and find the oldest launch time
  if [ -n "$instance_ids" ]; then
    oldest_launch_time=$(aws ec2 describe-instances --instance-ids $instance_ids --query 'Reservations[].Instances[].LaunchTime' --output text | sort | cut -d$'\t' -f 1)
  else
    oldest_launch_time=null
  fi

  # Highlight the oldest launch time if it's more than 2 days old
  if [ "$oldest_launch_time" != "null" ]; then
    launch_time_seconds=$(date -j -f '%Y-%m-%dT%H:%M:%S' "$oldest_launch_time" +%s 2>/dev/null)  # redicect to /dev/null to silence warning `Warning: Ignoring 6 extraneous characters in date string (+00:00)`
    now_seconds=$(date +%s)
    if (( ($now_seconds - ${launch_time_seconds:-0}) > (2 * 24 * 60 * 60) )); then
      oldest_launch_time=$(date -j -r "$launch_time_seconds" +"%Y-%m-%dT%H:%M:%S")
      oldest_launch_time="⚠️ $oldest_launch_time"
    fi
  fi

  # Get the number of instances in the Auto Scaling group
  instance_ids__arr=($instance_ids)
  instances_count=${#instance_ids__arr[@]}

  # Print the ASG name, the number of instances, and the oldest launch time
  echo "AutoScalingGroupName: $asg_name, OldestInstanceLaunchTime: $oldest_launch_time, InstancesCount: $instances_count"
done

unset AWS_DEFAULT_REGION
unset AWS_PROFILE