Welcome to session four: Auto Scaling Scaling Configuration. In this session, we will cover creating a scaling configuration, querying a scaling configuration, and deleting a scaling configuration. Creating a new scaling configuration can be done in two ways. The first is from the Scaling Groups page in the console by selecting the Add Scaling Configuration link. Or second, from within a Scaling Group page by selected the Configuration Source tab.

Selecting the Configuration Source tab allows more options. You can create scaling configurations by selecting a Launch Template. Selecting Scaling Configuration gives the options of creating, importing, and exporting the scaling configuration, and Update Image Task is where you can create custom images and replace instances in an existing scaling configuration.

A scaling configuration defines the configuration of the ECS instances which will be added to the scaling group by any scaling activities that are triggered. Auto Scaling automatically adds ECS instances into scaling groups according to the active scaling configuration. You can modify scaling configuration after it's created.

ECS instances created by the new scaling configuration will still work as expected, and you can create up to 10 scaling configurations for one scaling group. However, only one scaling configuration can be active at any time. In the Scaling Groups console page, select the Configuration Source Tab to see any scaling configurations that have been created and check the status column to see the status.

Scaling configurations have the following lifecycle states. There's just two: Active and Not Effective or Inactive. The scaling group will use a scaling configuration that is in an active state to create or remove ECS instances from the group. Not effective or inactive scaling configurations are still part of the group, but they're not used to create ECS instances. To change the active configuration, select the Apply link in the Actions column.

Deleting a scaling configuration. You cannot delete a scaling configuration if it is in an active state and the scaling group cannot contain instances which were created by the scaling configuration that you want to delete. For example, if a scaling group has two ECS instances in it that were created from the current scaling configuration that I want to delete, then first I need to remove those instances. I can then disable the scaling configuration and finally, once it's disabled, I'll be able to delete it.

That concludes this session on Auto Scaling Scaling Configuration. In the next session, I will demonstrate how to create and activate a scaling group.