I have created an ECS cluster, and deployed a 2-container task using a Service (during Service create I associate the Application Load Balancer – using target group of type IP – to it),
this works fine (I can access my DNS URL and it loads as expected).

I am now trying to use an AutoScalingGroup for automatically scaling instances (cluster autoscaling), based on CPU utilization.

I have created the ASG (desired instance count=1, max=4), but now need to create a dynamic scaling policy, based on CPU utilization.

If average instance CPU usage is over 50%, I want the ASG to add more instances using simple scaling.
(and if ave usage falls under 40, scale back in to min desired count again).

When I click on Create Cloudwatch alarm I get the following: Step 1 (I then click ‘Select Metric’):

My question is basically – what metric do I need to select to achieve the above CPU usage scaling?