The OpenStack Orchestration service, a tool for orchestrating clouds, automatically configures and deploys resources in stacks. The deployments can be simple, such as deploying WordPress on Ubuntu with an SQL back end, or complex, such as starting a server group that auto scales by starting and stopping using real-time CPU loading information from the Telemetry service.

Orchestration stacks are defined with templates, which are non-procedural documents. Templates describe tasks in terms of resources, parameters, inputs, constraints, and dependencies. When the Orchestration service was originally introduced, it worked with AWS CloudFormation templates, which are in the JSON format.

The Orchestration service also runs Heat Orchestration Template (HOT) templates that are written in YAML. YAML is a terse notation that loosely follows structural conventions (colons, returns, indentation) that are similar to Python or Ruby. Therefore, it is easier to write, parse, grep, generate with tools, and maintain source-code management systems.

Orchestration can be accessed through a CLI and RESTful queries. The Orchestration service provides both an OpenStack-native REST API and a CloudFormation-compatible Query API. The Orchestration service is also integrated with the OpenStack dashboard to perform stack functions through a web interface.

For more information about using the Orchestration service through the command line, see the Heat Command-Line Interface reference.