OpenStack Heat -- Orchestration Service

Introduction

Heat is OpenStack's native orchestration engine. It implements infrastructure-as-code through HOT (Heat Orchestration Template) files -- YAML documents that declaratively describe cloud resources and their relationships. Heat creates, updates, and deletes collections of resources (called "stacks") as atomic units, handling dependency ordering, rollback on failure, and lifecycle management automatically.

Heat is to OpenStack what CloudFormation is to AWS and Deployment Manager is to GCP. The critical difference: HOT templates are portable across any OpenStack deployment, and Heat's resource type registry is extensible -- operators can register custom resource types without modifying the core service. For users familiar with Terraform, Heat serves a similar role but is integrated directly into the OpenStack control plane, meaning it has native access to all OpenStack APIs without external provider configuration.

The stack lifecycle follows a state machine: CREATE_IN_PROGRESS, CREATE_COMPLETE, CREATE_FAILED, UPDATE_IN_PROGRESS, UPDATE_COMPLETE, UPDATE_FAILED, DELETE_IN_PROGRESS, DELETE_COMPLETE, DELETE_FAILED. Each state transition is atomic -- either all resources in a stack reach the target state or the stack rolls back to the previous known-good state.

Deploy

Heat deployment via Kolla-Ansible requires enabling the service in globals.yml:

# /etc/kolla/globals.yml
enable_heat: "yes"