OpenStack Heat is an orchestration service that allows you to automate the deployment and management of cloud infrastructure resources. The Heat service uses a template-based approach to describe and define the desired infrastructure configuration, which is then executed by the Heat engine.
The Heat engine is a key component of the Heat service in OpenStack. It is responsible for parsing and interpreting the templates written in HOT (Heat Orchestration Template) or AWS CloudFormation format, creating and managing the necessary resources, and coordinating the entire orchestration process.
Here are some key aspects and functions of the Heat engine:
- Template Parsing: The Heat engine receives templates provided by users and parses them to understand the structure, resource types, properties, and relationships defined in the template.
- Resource Handling: The Heat engine manages the lifecycle of resources defined in the templates. It creates, updates, and deletes resources as required based on the orchestration instructions provided in the template. Resources can include instances, volumes, networks, security groups, load balancers, and more.
- Dependency Resolution: The Heat engine determines the dependencies between resources based on the template specifications. It ensures that resources are created in the correct order and that all dependencies are met before proceeding with the orchestration.
- Resource Configuration: The Heat engine is responsible for configuring the properties and parameters of resources based on the values specified in the template. It interacts with other OpenStack services and APIs to set up the desired resource configurations.
- Scaling and Autohealing: Heat provides scaling capabilities, allowing you to define auto-scaling groups that automatically adjust the number of instances based on predefined conditions. The Heat engine monitors the state of the resources and performs scaling actions as required.
- Rollbacks and Error Handling: If an error occurs during the orchestration process, the Heat engine can perform rollback operations to revert the changes and bring the stack back to its previous state. It provides robust error handling and logging mechanisms to aid in troubleshooting and debugging.
- Integration with OpenStack: The Heat engine integrates with other OpenStack services such as Nova (compute), Neutron (networking), Cinder (block storage), and others. It leverages their APIs to create and manage the necessary resources during the orchestration process.
- High Availability: The Heat engine itself can be deployed in a highly available manner by configuring multiple instances behind a load balancer. This ensures that orchestration requests can be processed even if one of the instances becomes unavailable.
Overall, the Heat engine plays a crucial role in automating the deployment and management of complex cloud infrastructure using OpenStack Heat. It interprets templates, manages the lifecycle of resources, handles dependencies, and coordinates the entire orchestration process.