writing-workflow.md

Writing a Workflow

Any workflow comprises two building blocks: worker (targeted hardware) and a template.

Creating a worker

A worker is targeted hardware on which workflow needs to run. User need to push the hardware details as per the below command:

 $ tink hardware push "<targeted hardware data in json format>"

Creating a template

Consider a sample template like the following saved as /tmp/sample.tmpl.

version: "0.1"
name: ubuntu_provisioning
global_timeout: 2500
tasks:
    - name: "os-installation"
      worker: "{{.device_1}}"
      volumes:
          - /dev:/dev
          - /lib/firmware:/lib/firmware:ro
      environment:
          MIRROR_HOST: <MIRROR_HOST_IP>
      actions:
          - name: "disk-partition"
            image: disk-partition
            timeout: 600
            environment:
                MIRROR_HOST: <MIRROR_HOST_IP>
            volumes:
                - /statedir:/statedir
          - name: "install-root-fs"
            image: install-root-fs
            timeout: 600
          - name: "install-grub"
            image: install-grub
            timeout: 600
            volumes:
                - /statedir:/statedir

Key points:

• global_timeout is in seconds.
• Any worflow that exceeds the global timeout will be terminated and marked as failed.
• Each action has its own timeout. If an action reaches its timeout, it is marked as failed and so is the workflow.
• An action cannot have space (``) in its name.
• Environment variables and volumes at action level overwrites the values for duplicate keys defined at task level.

A worker can be accessed in a template like:

{{.device_1}}
{{.device_2}}

The following command creates a workflow template and returns a UUID:

 $ tink template create -n sample -p /tmp/sample.tmpl

Creating a workflow

We can create a workflow using the above created (or existing) template and worker.

 $ tink workflow create -t <template-uuid> -r '{worker machines in json format}'
 $ tink workflow create -t edb80a56-b1f2-4502-abf9-17326324192b -r '{"device_1":"mac/IP"}'

The above command returns a UUID for the workflow thus created. The workflow ID can be used for getting further details about a workflow. Please refer the Tinkerbell CLI reference for the same.

It's a good practice to verify that the worker have been well substituted in the template. In order to do so, use the following command:

 $ tink workflow get <workflow Id returned from the above command>

version: '0.1'
name: ubuntu_provisioning
global_timeout: 2500
tasks:
- name: "os-installation"
  worker: "98:03:9b:4b:c5:34"
  volumes:
    - /dev:/dev
    - /lib/firmware:/lib/firmware:ro
  environment:
    MIRROR_HOST: 192.168.1.2
  actions:
  - name: "disk-partition"
    image: disk-partition
    timeout: 600
    environment:
       MIRROR_HOST: 192.168.1.3
    volumes:
      - /statedir:/statedir
  - name: "install-root-fs"
    image: install-root-fs
    timeout: 600
  - name: "install-grub"
    image: install-grub
    timeout: 600
    volumes:
      - /statedir:/statedir

Notice how worker is set to the MAC address we had defined in the input while creating a workflow.