AWS CloudWatch is the service responsible for publishing metrics for auto scaling. It plays a central role in monitoring the performance of AWS resources and applications. CloudWatch collects and tracks metrics, which can then be used to trigger actions in Auto Scaling Groups, such as scaling in or scaling out based on demand.
When configured, Auto Scaling can use the metrics provided by CloudWatch to determine when to add or remove instances. For example, if the CPU usage of instances in an Auto Scaling Group exceeds a certain threshold, CloudWatch can signal the Auto Scaling service to launch additional instances to handle the increased load.
The integration between CloudWatch and Auto Scaling ensures that applications can automatically adjust to the conditions of demand, facilitating efficient resource management and cost control in cloud environments.