OVH Guides

Deploying an infrastructure with variables and formatted outputs using OpenStack Heat (BETA)

Find out how to process environment variables using the modularity of Heat templates

Last updated June 20th 2018

Objective

We recommend starting off by reading our guide on Deploying a basic infrastructure with OpenStack Heat, which covers how to use Heat for creating and manipulating simple stacks. In this guide, we will go a step further by using parameters in these stacks.

Find out how to format the output, so that you can use this information on the resources you have deployed.

Requirements

  • access to the OVH Control Panel
  • a Public Cloud project
  • an OpenStack user account
  • how to manipulate YAML files
  • sign up your Public Cloud project for the beta test

Instructions

Manage the parameters

Using variables, you can edit the parameters for stacks in Heat. We will add these into the file parameter-template.yaml:

heat_template_version: 2014-10-16

description: Simple template to deploy a single compute instance with an attached volume

parameters:
  key_name:
    type: string
    description: Name of a KeyPair to enable SSH access to the instance
    default: heat_key

  image_id:
    type: string
    description: Name of a cloud image in the catalog
    default: Debian 9

  size_gb:
    type: string
    description: Size of the volume
    default: 10

resources:
  my_instance:
    type: OS::Nova::Server
    properties:
      key_name: { get_param: key_name }
      image: { get_param: image_id }
      flavor: c2-7
      networks:
        - network: Ext-Net

  my_volume:
    type: OS::Cinder::Volume
    properties:
      size: { get_param: size_gb }

  my_attachment:
      type: OS::Cinder::VolumeAttachment
      properties:
        instance_uuid:  { get_resource: my_instance }
        volume_id: { get_resource: my_volume }
        mountpoint: /dev/vdb

The entries with { get_param: xxx } represent parameters you can avoid when you create the stack. This way, you can use the same template to create different stacks:

$ openstack stack create -t parameter-template.yaml --parameter key_name=heat_key --parameter image_id="Centos 7" --parameter size_gb=50 second-stack
+---------------------+-----------------------------------------------------------------------------+
| Field               | Value                                                                       |
+---------------------+-----------------------------------------------------------------------------+
| id                  | 35ba3489-f48f-47fc-a0ed-cf17ad302e9c                                        |
| stack_name          | second-stack                                                                |
| description         | Simple template to deploy a single compute instance with an attached volume |
| creation_time       | 2018-03-28T14:34:15Z                                                        |
| updated_time        | None                                                                        |
| stack_status        | CREATE_IN_PROGRESS                                                          |
| stack_status_reason | Stack CREATE started                                                        |
+---------------------+-----------------------------------------------------------------------------+
$ openstack stack create -t parameter-template.yaml --parameter key_name=heat_key --parameter image_id="Ubuntu 17.10" --parameter size_gb=10 third-stack
+---------------------+-----------------------------------------------------------------------------+
| Field               | Value                                                                       |
+---------------------+-----------------------------------------------------------------------------+
| id                  | 10f5926e-fc7b-4ca0-914e-d3a964d0796a                                        |
| stack_name          | third-stack                                                                 |
| description         | Simple template to deploy a single compute instance with an attached volume |
| creation_time       | 2018-03-28T14:35:49Z                                                        |
| updated_time        | None                                                                        |
| stack_status        | CREATE_IN_PROGRESS                                                          |
| stack_status_reason | Stack CREATE started                                                        |
+---------------------+-----------------------------------------------------------------------------+

Go further with the parameters in the post-installation scripts

At this point, it would be helpful for you to get output information once you have launched your stack, so that you can use this information for other processing operations.

Modify the file to include the definition of outputs.

heat_template_version: 2014-10-16

description: Simple template to deploy a single compute instance with an attached volume

parameters:
  key_name:
    type: string
    description: Name of a KeyPair to enable SSH access to the instance
    default: heat_key

  image_id:
    type: string
    description: Name of a cloud image in the catalog
    default: Debian 9

  size_gb:
    type: string
    description: Size of the volume
    default: 10

resources:
  my_instance:
    type: OS::Nova::Server
    properties:
      key_name: { get_param: key_name }
      image: { get_param: image_id }
      flavor: c2-7
      networks:
        - network: Ext-Net

  my_volume:
    type: OS::Cinder::Volume
    properties:
      size: { get_param: size_gb }

  my_attachment:
      type: OS::Cinder::VolumeAttachment
      properties:
        instance_uuid:  { get_resource: my_instance }
        volume_id: { get_resource: my_volume }
        mountpoint: /dev/vdb

outputs:
 server:
   description: This is a list of server names.
   value: { get_attr: [my_instance, name]}
 server_ip:
   description: This is a list of first ip addresses of the server.
   value: { get_attr: [my_instance, networks, Ext-Net]}

Once you have created the stack, use openstack stack output show to retrieve the formatted information:

$ openstack stack output show fourth-stack server_ip
+--------------+----------------------------------------------------+
| Field        | Value                                              |
+--------------+----------------------------------------------------+
| description  | This is a list of first ip addresses of the server |
| output_key   | server_ip                                          |
| output_value | [u'2001:41d0:801:1000::26', u'54.37.0.132']        |
+--------------+----------------------------------------------------+
$ openstack stack output show fourth-stack server
+--------------+-------------------------------------+
| Field        | Value                               |
+--------------+-------------------------------------+
| description  | This is a list of server names.     |
| output_key   | server                              |
| output_value | four-stack-my_instance-jmeobt3egom3 |
+--------------+-------------------------------------+

You can find out more by reading the official OpenStack documentation, but these guides should be enough to help you build your first infrastructure definitions using code.

Go further

Join our community of users on https://community.ovh.com/en/.


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