Cluster Type Definition

There are three key pieces to a Cluster Type Definition:

1. Heat Stack template - The HOT file that Magnum will use to generate a cluster using a Heat Stack.
2. Template definition - Magnum’s interface for interacting with the Heat template.
3. Definition Entry Point - Used to advertise the available Cluster Types.

The Heat Stack Template

The Heat Stack Template is where most of the real work happens. The result of the Heat Stack Template should be a full Container Orchestration Environment.

The Template Definition

Template definitions are a mapping of Magnum object attributes and Heat template parameters, along with Magnum consumable template outputs. A Cluster Type Definition indicates which Cluster Types it can provide. Cluster Types are how Magnum determines which of the enabled Cluster Type Definitions it will use for a given cluster.

The Definition Entry Point

Entry points are a standard discovery and import mechanism for Python objects. Each Template Definition should have an Entry Point in the magnum.template_definitions group. This example exposes it’s Template Definition as example_template = example_template:ExampleTemplate in the magnum.template_definitions group.

Installing Cluster Templates

Because Cluster Type Definitions are basically Python projects, they can be worked with like any other Python project. They can be cloned from version control and installed or uploaded to a package index and installed via utilities such as pip.

Enabling a Cluster Type is as simple as adding it’s Entry Point to the enabled_definitions config option in magnum.conf.:

# Setup python environment and install Magnum

$ virtualenv .venv
$ source .venv/bin/active
(.venv)$ git clone https://github.com/openstack/magnum.git
(.venv)$ cd magnum
(.venv)$ python setup.py install

# List installed templates, notice default templates are enabled

(.venv)$ magnum-template-manage list-templates
Enabled Templates
  magnum_vm_atomic_k8s: /home/example/.venv/local/lib/python2.7/site-packages/magnum/templates/kubernetes/kubecluster.yaml
  magnum_vm_coreos_k8s: /home/example/.venv/local/lib/python2.7/site-packages/magnum/templates/kubernetes/kubecluster-coreos.yaml
Disabled Templates

# Install example template

(.venv)$ cd contrib/templates/example
(.venv)$ python setup.py install

# List installed templates, notice example template is disabled

(.venv)$ magnum-template-manage list-templates
Enabled Templates
  magnum_vm_atomic_k8s: /home/example/.venv/local/lib/python2.7/site-packages/magnum/templates/kubernetes/kubecluster.yaml
  magnum_vm_coreos_k8s: /home/example/.venv/local/lib/python2.7/site-packages/magnum/templates/kubernetes/kubecluster-coreos.yaml
Disabled Templates
  example_template: /home/example/.venv/local/lib/python2.7/site-packages/ExampleTemplate-0.1-py2.7.egg/example_template/example.yaml

# Enable example template by setting enabled_definitions in magnum.conf

(.venv)$ sudo mkdir /etc/magnum
(.venv)$ sudo bash -c "cat > /etc/magnum/magnum.conf << END_CONF
[bay]
enabled_definitions=magnum_vm_atomic_k8s,magnum_vm_coreos_k8s,example_template
END_CONF"

# List installed templates, notice example template is now enabled

(.venv)$ magnum-template-manage list-templates
Enabled Templates
  example_template: /home/example/.venv/local/lib/python2.7/site-packages/ExampleTemplate-0.1-py2.7.egg/example_template/example.yaml
  magnum_vm_atomic_k8s: /home/example/.venv/local/lib/python2.7/site-packages/magnum/templates/kubernetes/kubecluster.yaml
  magnum_vm_coreos_k8s: /home/example/.venv/local/lib/python2.7/site-packages/magnum/templates/kubernetes/kubecluster-coreos.yaml
Disabled Templates

# Use --details argument to get more details about each template

(.venv)$ magnum-template-manage list-templates --details
Enabled Templates
  example_template: /home/example/.venv/local/lib/python2.7/site-packages/ExampleTemplate-0.1-py2.7.egg/example_template/example.yaml
     Server_Type  OS       CoE
     vm         example  example_coe
  magnum_vm_atomic_k8s: /home/example/.venv/local/lib/python2.7/site-packages/magnum/templates/kubernetes/kubecluster.yaml
     Server_Type   OS             CoE
     vm        fedora-atomic  kubernetes
  magnum_vm_coreos_k8s: /home/example/.venv/local/lib/python2.7/site-packages/magnum/templates/kubernetes/kubecluster-coreos.yaml
     Server_Type  OS      CoE
     vm         coreos  kubernetes
Disabled Templates