Heat Template Tips

Heat templates are a way of defining sets of resources in the cloud. These templates can help you manage groups of servers, volumes, ssh keys, networks and more. These groups of resources are called a Stacks. For an overview and documentation on the template structure, you can visit the links below. To view/create your own Stacks follow this link.

Template Overview

List of Resource Types and Examples

The template generator does not generate valid templates. You can use it to help generate a skeleton for a template, but expect to have to go back through and fix mistakes in the resources' keys/values.

Tips

Intrinsic functions are a great way to make templates more flexible. Use them to get parameters set by users (get_param), reference other resources from the template (get_resource and get_attr), dynamically construct strings (str_replace) and more.
Provide instances with scripts that run on boot using the user_data key.

### Script with no dynamic string replacement ###
resources:

  the_server:
    type: OS::Nova::Server
    properties:
      # flavor, image etc
      user_data: |
        #!/bin/bash
        echo "Running boot script"
        # ...

###Takes user input for value of "foo" and uses that value as $FOO in the bootup script
parameters:
  foo:
    default: bar

resources:

  the_server:
    type: OS::Nova::Server
    properties:
      # flavor, image etc
      user_data:
        str_replace:
          template: |
            #!/bin/bash
            echo "Running boot script with $FOO"
            # ...
          params:
           $FOO: {get_param: foo}

To boot an instance from a volume or snapshot, used the block_device_mapping key and do not specify an image.

block_device_mapping: [{"snapshot_id": "snapshot-id-here", "device_name": "vda"}]

If you boot an instance from a snapshot this way, Heat will automatically create a volume from the snapshot and attach it to the instance. However, Heat will not automatically delete the volume when the stack is deleted. To get around this, you can define a volume in the template based on a snapshot and use that volume to boot the instance. This way, the volume is deleted with the rest of the resources when the stack is deleted.