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Version: v4

Container Orchestration with OpenStack Heat

Introduction​

This guide provides an introduction to Heat Orchestration through OpenStack. Outlined within this article are the basics of Orchestration and the mechanics of the Heat Orchestration Engine. Then we review a sample of a Heat Orchestration Template and provide the appropriate syntax. Lastly, we cover how to deploy a template and check the status of a Heat Stack.

Overview of Heat Orchestration​

Orchestration tools utilize automation to deploy, manage, scale, and network containers. Within OpenStack, the primary orchestration component is Heat. Heat uses an orchestration engine for the automation of resources, infrastructure, applications, and services. These created resources are referred to as Stacks. Heat Stacks are deployed using Heat Orchestration Templates also referred to as HOT templates. HOT templates are created in YAML that passes instructions to the Heat Engine specifying the resources to be deployed.

How to View Heat Stacks in the Dashboard​

This page lists every stack in the current project and is where new stacks are created.

Go to Project -> Orchestration -> Stacks.

Stacks page in Horizon

Architecture​

Heat API receives rest API calls from the following sources: the dashboard, HOT Templates, and through the Heat Client. The Heat API is then passed to RabbitMQ or another message broker which activates the Heat Orchestration Engine. The Heat Orchestration Engine then connects to resources including Nova, Glance, Neutron, and Cinder and parses instructions from the HOT template for functions and parameters. These functions and parameters are then used to create resources known as stacks.

Heat Orchestration Template Components​

Central to the deployment of Heat and the creation of Stacks is the use of templates. Heat Templates are written in YAML with the following structure:

Template Version​

The template version is formatted as date and corresponds to different versions of heat. The template version tells Heat how the template will be structured, what features can be validated, and what resources can be created. Currently, the latest template version that is supported is 2018-08-31 (rocky).

Description​

Although optional, a description is highly recommended as it outlines the intended function of the template. This is particularly useful for templates that are not frequently used or are intended to be shared among various members of a team or project.

Parameters​

Parameters are optional but allow a user to pass additional values to the template. These values are used to overwrite any default settings that are specified in the resources section.

Resources​

Resources are what are ultimately created by the Heat Orchestration Engine. These values can be default values or input from the parameters above.

Output​

Output in a Heat Template is optional. However, you can pass values from Heat upon execution of the template. These values are accessed through Heat API or client tools.

Sample Heat Orchestration Template​

The following is an example of a Heat Orchestration Template to deploy an instance. In this example, all resources receive their values fed separately as parameters. When formatting parameters, each parameter is grouped in a nested block. The first line contains the name of the parameter and additional attributes are grouped below each element.

Attributes​

  • Parameter Name: Name of Parameter
  • Type: Required value that supports the following types: string, comma_delimited_list, json, boolean
  • Label: Optional attribute, creates a name for the parameter for additional readability
  • Description: Optional attribute, creates a description for parameter
  • Default: Optional attribute, default values for parameters if input is not specified by the user

Example Heat Orchestration Template:

heat_template_version: 2018-03-02

description: Simple template to deploy a single instance

parameters:
  key_name:
    type: string
    label: Key Name
    description: Name of key-pair to be used for compute instance
  image_id:
    type: string
    label: Image ID
    description: Image to be used for compute instance
  instance_type:
    type: string
    label: Instance Type
    description: Type of instance (flavor) to be used
  network_name:
    type: string
    description: The network to be used
  security_groups:
    type: comma_delimited_list
    description: Name of the Security Group

resources:
  my_instance:
    type: OS::Nova::Server
    properties:
      key_name: { get_param: key_name }
      image: { get_param: image_id }
      networks:
        - network: { get_param: network_name }
      flavor: { get_param: instance_type }
      security_groups: { get_param: security_groups }

Deploying a Heat Template​

Confirm you have the correct project selected.

Go to Project -> Orchestration -> Stacks and click Launch Stack.

Select Template dialog in Horizon

Figure 1: Select Template

  • Template Source: File to upload the template, or Direct Input to paste it.
  • Environment Source: optional.

Click Next. Horizon reads the template's parameters section and renders an input for each one, alongside Stack Name, Creation Timeout, Rollback On Failure, and the password for your user.

Click Launch to create the stack.

Viewing Recently Deployed Stacks​

Switch to the project where the stack was created. The list shows the stack and its current status. Click the stack name for its detail page, which includes a copy of the template used to create it.

Go to Project -> Orchestration -> Stacks.

Stacks list in Horizon

Figure 2: Stacks Created within Admin Project

The detail page tabs are Topology, Overview, Resources, Events, and Template.

Stack detail page in Horizon

Figure 3: Overview of Test Stack

Additional Resources for OpenStack Heat Service​

For the latest on OpenStack Heat Documentation visit Welcome to the Heat documentation. Further reading regarding Heat architecture can be found at Heat architecture. Additionally, OpenStack has a guide for creating your first stack through heat that can be found at Creating your first stack.