Openstack Heat - separate templates - openstack

Question

I am looking for the best way of creating a stack, in a number of separate steps.
I would like in the first template, to only get up the compute nodes and the network configuration.
In the second template, I would like to create the storage nodes and attach them to the already existing compute nodes.
What do you think is the best way to do this?

Answer 1

Following is one possible approach.
1) Define first template for your compute nodes and network configuration. But define outputs in your first template to expose your compute node IDs. For example, if you create a OS::Nova::Server with name mynode1, you can expose its ID as the output for that template as follows:
outputs:
mynode1_id:
description: ID of mynode1
value: {getattr: [mynode1, id]}
Once you instantiate a heat stack, say mystack1, with this first template, then you can access the ID of mynode1 as follows:
heat output-show mystack1 mynode1_id
2) Create your second template for storage with IDs of your compute nodes from step1 as input parameters. For example:
parameters:
mynode1_id:
type: string
description: ID for mynode1
Then you can use that in your "resources:" section as follows:
resources:
...
...
my_volume_attach:
type: OS::Cinder::VolumeAttachment
properties:
instance_uuid: {get_param: mynode1_id}
...
3) Invoke your second heat stack creation as follows:
heat stack-create -f second-template.yaml -P mynode1_id=`heat output-show mystack1 mynode1_id` mystack2

Answer 2

You might also want to define dependencies between your resources, using the depends_on attribute.
From your description it doesn't seem like using several templates is the correct solution.
for example - if you want objects 3,4 created after objects 1,2, you can define a template as follows:
heat_template_version: '2015-10-15'
parameters:
param1:
type: string
description: just an example of parameter
resources:
object1:
type: OS::Neutron::XXX
properties:
property: XXX
description: object1
object2:
type: OS::Neutron::XXX
properties:
property: XXX
description: object2
object3:
type: OS::Nova::XXX
properties:
property: XXX
description: object3
depends_on: object1
object4:
type: OS::Nova::XXX
properties:
property: XXX
description: object4
depends_on: object1