Steps

In this example, we'll see how to create multi-step workflows, how to define more than one template in a workflow spec, and how to create nested workflows. Be sure to read the comments as they provide useful explanations.

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: steps-
spec:
  entrypoint: hello-hello-hello

  # This spec contains two templates: hello-hello-hello and whalesay
  templates:
  - name: hello-hello-hello
    # Instead of just running a container
    # This template has a sequence of steps
    steps:
    - - name: hello1            # hello1 is run before the following steps
        template: whalesay
        arguments:
          parameters:
          - name: message
            value: "hello1"
    - - name: hello2a           # double dash => run after previous step
        template: whalesay
        arguments:
          parameters:
          - name: message
            value: "hello2a"
      - name: hello2b           # single dash => run in parallel with previous step
        template: whalesay
        arguments:
          parameters:
          - name: message
            value: "hello2b"

  # This is the same template as from the previous example
  - name: whalesay
    inputs:
      parameters:
      - name: message
    container:
      image: docker/whalesay
      command: [cowsay]
      args: ["{{inputs.parameters.message}}"]

The above workflow spec prints three different flavors of "hello". The hello-hello-hello template consists of three steps. The first step named hello1 will be run in sequence whereas the next two steps named hello2a and hello2b will be run in parallel with each other. Using the argo CLI command, we can graphically display the execution history of this workflow spec, which shows that the steps named hello2a and hello2b ran in parallel with each other.

STEP            TEMPLATE           PODNAME                 DURATION  MESSAGE
 ✔ steps-z2zdn  hello-hello-hello
 ├───✔ hello1   whalesay           steps-z2zdn-27420706    2s
 └─┬─✔ hello2a  whalesay           steps-z2zdn-2006760091  3s
   └─✔ hello2b  whalesay           steps-z2zdn-2023537710  3s

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