Template Invocators Types Steps

Explore the Steps template invoker type in Argo Workflows. Steps templates let you compose multi-step workflows that run tasks both sequentially and in parallel. This example workflow, named “Cosmic Move”, shows how a Steps template orchestrates reusable templates (here, cow-says) into a sequence of step groups with parallel execution inside groups.

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: cosmic-moo-
spec:
  entrypoint: triple-moo
  templates:
  - name: triple-moo
    steps:
    - - name: first-moo
        template: cow-says
        arguments:
          parameters:
          - name: message
            value: "Cosmic Ranch!"
    - - name: parallel-moo-a
        template: cow-says
        arguments:
          parameters:
          - name: message
            value: "Galaxy Moo!"
      - name: parallel-moo-b
        template: cow-says
        arguments:
          parameters:
          - name: message
            value: "Milky Whey!"
  - name: cow-says
    inputs:
      parameters:
      - name: message
    container:
      image: rancher/cowsay
      command: ["cowsay"]
      args: ["{{inputs.parameters.message}}"]

How this workflow is wired:

The workflow entrypoint is triple-moo.
triple-moo uses a steps block to orchestrate calls to the reusable cow-says template.
cow-says is a simple container task that runs cowsay with the supplied message parameter.

Understanding the steps structure

steps is a list of step-groups (a list of lists).
- Each top-level list item (each top-level -) is a step-group that executes in sequence.
- Within a step-group, each inner - is an individual step that runs in parallel with the other inner steps in that group.

Think of steps as a sequence of step-groups: each top-level dash creates a group that runs one after another; steps inside the same group (inner dashes) run concurrently.

Execution semantics (summary):

Top-level elements (step-groups) run one after another (sequential).
Inner list elements inside a group run at the same time (parallel).
The workflow advances to the next group only after every step in the current group finishes.

Example: what happens in the “Cosmic Move” workflow

First step-group:
- first-moo runs by itself. The workflow waits until it completes.
Second step-group:
- parallel-moo-a and parallel-moo-b run concurrently. The workflow proceeds only after both finish.

When you inspect a running workflow with argo, the execution tree shows the sequence and parallel steps. Example output:

$ argo -n argo get cosmic-moo-k2kxq

STEP                    TEMPLATE       PODNAME
✓ cosmic-moo-k2kxq      triple-moo
├─✓ first-moo            cow-says       cosmic-moo-k2kxq-cow-says-2575730875
├─✓ parallel-moo-a       cow-says       cosmic-moo-k2kxq-cow-says-1190566453
└─✓ parallel-moo-b       cow-says       cosmic-moo-k2kxq-cow-says-1140233596

Quick reference table

Concept	Behavior	Example
Step-group (top-level item)	Runs sequentially relative to other groups	First group contains `first-moo`
Steps in a group (inner items)	Run in parallel with each other	`parallel-moo-a` and `parallel-moo-b`
Entry point	Template name used to start the workflow	`entrypoint: triple-moo`
Reusable template	Called by steps with parameters	`cow-says` accepts `message` parameter

Best practices

Use Steps templates when you need explicit ordering and occasional parallelism between tasks.
Keep reusable work in separate templates and pass parameters for customization.
Use clear step names to make the execution tree easy to read when inspecting runs with argo get.

Links and references

Watch Video

Demo Template ContainerSet

Demo Template Suspend

ArgoCD

Argo Workflow

Argo Rollouts

Argo Events

Introduction

Template Invocators Types Steps

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