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Heat (OSS Project)

Heat is an orchestration (infrastructure automation) component of OpenStack that provisions and manages composite cloud applications using declarative templates.

  • Template-driven orchestration of cloud resources (infrastructure automation)
  • Support for OpenStack-native Heat Orchestration Template (HOT) format (configuration as code)
  • Management of stacks that group interdependent resources into a single lifecycle unit (cloud resource management)
  • Integration with core OpenStack services such as compute, networking, and storage (cloud platform integration)
  • Autoscaling, dependency handling, and update mechanisms for template-defined resources (cloud operations automation)

More About Heat (OSS Project)

Heat is the orchestration (infrastructure automation) project within OpenStack that enables users to describe and manage composite cloud applications and infrastructure using declarative templates. It provides a framework where application infrastructure is defined as code and instantiated as a stack of OpenStack resources, enabling repeatable deployments and lifecycle management across an OpenStack cloud.

The core concept in Heat is the stack (cloud resource management), which is a collection of OpenStack resources such as servers, networks, subnets, volumes, and security groups, managed as a single logical entity. Stacks are defined through templates that specify resources, their properties, dependencies, and outputs. Heat interprets these templates and communicates with underlying OpenStack services to create, update, or delete the corresponding resources in the correct order, based on declared dependencies.

Heat uses the Heat Orchestration Template format, or HOT (configuration as code), as its primary template language. HOT is a YAML-based, declarative template syntax tailored for OpenStack resources and orchestration behavior. Templates can include parameters, conditions, resource groups, mappings, and outputs. They can also reference intrinsic functions to handle value substitution, attribute lookups, and resource dependency resolution, allowing template authors to model complex topologies and configuration logic.

Operationally, Heat provides capabilities such as stack updates, rollbacks, and autoscaling (cloud operations automation). Users can update an existing stack by providing an updated template, and Heat computes the changes required to move the running stack to the new desired state. Autoscaling is enabled by defining scaling policies and alarms that adjust resource counts based on metrics or external signals. Heat also manages resource cleanup on stack deletion and tracks stack state for auditing and troubleshooting.

In enterprise environments, Heat is used to standardize and codify infrastructure deployments on OpenStack (cloud platform integration). Infrastructure and application teams can maintain vetted templates in source control, use them to instantiate development, test, and production environments, and integrate stack operations into Continuous Integration and Continuous Deployment (CI/CD) pipelines and IT automation workflows. Heat’s interaction with core OpenStack APIs provides a consistent orchestration layer for compute, networking, and storage resources within the OpenStack ecosystem.

From a directory and taxonomy perspective, Heat is categorized as an orchestration engine and Infrastructure-as-Code (IaC) tool for OpenStack clouds (infrastructure automation). It operates alongside other OpenStack services to provide template-based provisioning, multi-resource dependency management, and lifecycle control for cloud-native and traditional workloads deployed on OpenStack-based infrastructure.