If a layer has auto healing enabled, AWS OpsWorks Stacks automatically replaces the layer’s failed instances:
The “auto-scaled” word in the options actually refers to Automatic load-based scaling in OpsWorks and not the actual EC2 Auto Scaling group. Please see the reference below from the official AWS Documentation to view the difference between these two :
Automatic load-based scaling uses load metrics that are averaged across all running instances. If the metrics remain between the specified thresholds, AWS OpsWorks Stacks does not start or stop any instances. With auto healing, on the other hand, AWS OpsWorks Stacks automatically starts a new instance with the same configuration when an instance stops responding. The instance may not be able to respond due to a network issue or some problem with the instance.
For example, suppose that your CPU upscaling threshold is 80%, and then one instance stops responding.
If auto healing is disabled, and the remaining running instances are able to keep average CPU utilization below 80%, AWS OpsWorks Stacks does not start a new instance. It starts a replacement instance only if the average CPU utilization across the remaining instances exceeds 80%.
If auto healing is enabled, AWS OpsWorks Stacks starts a replacement instance irrespective of the load thresholds.
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Jon Bonso @ Tutorials Dojo