confusion on how asg decides to scale with a mixed instance policy and multiple overrides

[dss010101]

I have code that looks like below. When i apply this, initially there is one instance type of t3.micro created. When it scales, the next instance is still t3.micro. and if it scales once more the max capacity, that instance is still t3.micro.

What i would expect is the first instance would use the 'default' template, which should be t2.micro.
I would then want the next to be the first override, which is t3.micro.
lastly, on the 3rd scale up event, ideally i would like to see the 2nd override go into effect - which would be t3a.small.

How does this work and how would i achieve what im looking for above?

resource "aws_launch_template" "default" {
  name                   = "default-template"
  vpc_security_group_ids = var.security_group_ids
  image_id               = var.default.ami
  instance_type          ="t2.micro"
  key_name               = aws_key_pair.auth_key.id
  user_data              = base64encode(var.default.user_data)
}

resource "aws_launch_template" "scaleup" {
  name                   = "scaleup-template"
  vpc_security_group_ids = var.security_group_ids
  image_id               = var.scaleup.ami
  instance_type          = "t2.small"
  key_name               = aws_key_pair.auth_key.id
  user_data              = base64encode(var.scaleup.user_data)
}


resource "aws_autoscaling_group" "asg" {
  name                      = "asg"
  vpc_zone_identifier  = [var.subnet_ids]
  min_size                  = 1
  max_size                  = 3
  desired_capacity          = 1

  mixed_instances_policy {
    launch_template {
      launch_template_specification {
        launch_template_id = aws_launch_template.default.id
      }
      override {
        instance_type     = "t3.micro"
        weighted_capacity = "1"
        launch_template_specification {
          launch_template_id = aws_launch_template.scaleup.id
        }
      }
      override {
        instance_type     = "t3a.small"
        weighted_capacity = "1"
      }
    }
  }
}

[tim-finnigan]

Hi @dss010101 — it looks like the snippet you provided is using Terraform rather than the AWS CLI. You may want to reach out here instead: https://www.terraform.io/community. For general AWS questions you could also try the re:Post forums: https://repost.aws/.

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.