Which component is responsible for handling auto-scaling policies in OpenStack?

The component responsible for handling auto-scaling policies in OpenStack is Heat. Heat is the orchestration service in OpenStack that allows users to define the infrastructure and services they want to deploy in a template format. This includes not only the initial provisioning of resources but also the management and scaling of those resources according to defined policies.

With Heat, users can set up auto-scaling rules that monitor resource usage and automatically expand or contract the infrastructure as needed. This means that if a particular application instance reaches its maximum capacity, Heat can launch new instances to distribute the load, thereby ensuring optimal performance without manual intervention. Heat essentially integrates with other OpenStack components to coordinate and manage these scaling actions.

The other components mentioned serve different purposes within the OpenStack ecosystem. For example, Ceilometer is primarily focused on telemetry and gathering usage statistics, Nova is responsible for managing compute resources and instances, while Neutron deals with networking services. Therefore, while all these components play critical roles in an OpenStack environment, it is Heat that specifically handles auto-scaling, making it the correct answer to this question.