give index number to ec2 instances of auto scaling group

Question

i have an autoscaling group in AWS.

i want/need to be able to "number" those instances. i'll explain: lets say the ASG raise 5 instances. i want to be able to name those instance as follows: instance-name-0 instance-name-1 ... instance-name-4

is there any way to keep such numbering on the instances? (including when increasing/decreasing the desired count of the instances?)

and extra question of the same nature: how can i do that with a Spot Fleet? (give numbers to the instances, that will hold even after changes in the instances - including spot termination and change in scale)

i kinda believe that there is no such easy way to do what i want, or even hard way - without possible bugs and/or overhead, but i ask anyway - maybe i'll be surprised :)

thanks!

Answer 1

The simplest way to do this would be to create a EventBridge event rule that will apply whenever an instance is launched or terminated successfully. The event would look something like the below:

{
  "source": [
    "aws.autoscaling"
  ],
  "detail-type": [
    "EC2 Instance Launch Successful",
    "EC2 Instance Terminate Successful"
  ],
  "detail": {
    "AutoScalingGroupName": [
      "YOUR-ASG-NAME-HERE"
    ]
  }
}

By adding a target of a Lambda function whenever this event triggers you would be able to review the instances that exist and then apply the logic as you deem fit.

One thing I will mention about naming each instance is that it generally feeds into the concept of pets vs cattle.