Orchestration is an orchestration engine that provides the possibility to launch multiple composite cloud applications based on templates in the form of text files that can be treated like code. A native Heat Orchestration Template (HOT) format is evolving, but it also endeavors to provide compatibility with the AWS CloudFormation template format, so that many existing CloudFormation templates can be launched on OpenStack.

Orchestration is a tool for orchestrating clouds that automatically configures and deploys resources in stacks. Such deployments can be simple — like deploying WordPress on Ubuntu with a SQL back end. And they can be quite complex, like launching a group of servers that autoscale: starting and stopping based on realtime CPU loading information from the Telemetry module. Orchestration stacks are defined with templates, which are non-procedural documents describing tasks in terms of resources, parameters, inputs, constraints and dependencies. When Orchestration module was originally introduced, it worked with AWS CloudFormation templates, which are in JSON format. Now, Orchestration also executes HOT (Heat Orchestration Template) templates, written in YAML: a terse notation that loosely follows Python/Ruby-type structural conventions (colons, returns, indentation) so it’s more easily to write, parse, grep, generate with tools, and maintain with source-code management systems. Orchestration can be accessed via the CLI, and using RESTful queries. Orchestration module provides both an OpenStack-native ReST API and a CloudFormation-compatible Query API. Orchestration is also integrated with OpenStack dashboard in order to launching stacks from templates through web-interface. For more details how to use Orchestration module command-line see OpenStack Command line interface reference