Intermediate Parameters

v3.4 and after

Traditionally, Argo workflows has supported input parameters from UI only when the workflow starts, and after that, it's pretty much on autopilot. But, there are a lot of use cases where human interaction is required.

This interaction is in the form of providing input text in the middle of the workflow, choosing from a dropdown of the options which a workflow step itself is intelligently generating.

A similar feature which you can see in jenkins is pipeline-input-step

Example use cases include:

• A human approval before doing something in production environment.
• Programmatic generation of a list of inputs from which the user chooses. Choosing from a list of available databases which the workflow itself is generating.

This feature is achieved via suspend template.

The workflow will pause at a Suspend node, and user will be able to update parameters using fields type text or dropdown.

Intermediate Parameters Approval Example

• The below example shows static enum values approval step.
• The user will be able to choose between [YES, NO] which will be used in subsequent steps.

entrypoint: cicd-pipeline
templates:
   - name: cicd-pipeline
     steps:
        - - name: deploy-pre-prod
            template: deploy
        - - name: approval
            template: approval
        - - name: deploy-prod
            template: deploy
            when: '{{steps.approval.outputs.parameters.approve}} == YES'
   - name: approval
     suspend: {}
     inputs:
        parameters:
           - name: approve
             default: 'NO'
             enum:
                - 'YES'
                - 'NO'
     outputs:
        parameters:
           - name: approve
             valueFrom:
                supplied: {}
   - name: deploy
     container:
        image: 'argoproj/argosay:v2'
        command:
           - /argosay
        args:
           - echo
           - deploying

Intermediate Parameters DB Schema Update Example

• The below example shows programmatic generation of enum values.
• The generate-db-list template generates an output called db_list.
• This output is of type json.
• Since this json has a key called enum, with an array of options, the UI will parse this and display it as a dropdown.
• The output can be any string also, in which case the UI will display it as a text field. Which the user can later edit.

entrypoint: db-schema-update
templates:
    - name: db-schema-update
      steps:
        - - name: generate-db-list
            template: generate-db-list
        - - name: choose-db
            template: choose-db
            arguments:
              parameters:
                - name: db_name
                  value: '{{steps.generate-db-list.outputs.parameters.db_list}}'
        - - name: update-schema
            template: update-schema
            arguments:
              parameters:
                - name: db_name
                  value: '{{steps.choose-db.outputs.parameters.db_name}}'
    - name: generate-db-list
      outputs:
        parameters:
          - name: db_list
            valueFrom:
              path: /tmp/db_list.txt
      container:
        name: main
        image: 'argoproj/argosay:v2'
        command:
          - sh
          - '-c'
        args:
          - >-
            echo "{\"enum\": [\"db1\", \"db2\", \"db3\"]}" | tee /tmp/db_list.txt
    - name: choose-db
      inputs:
        parameters:
          - name: db_name
      outputs:
        parameters:
          - name: db_name
            valueFrom:
              supplied: {}
      suspend: {}
    - name: update-schema
      inputs:
        parameters:
          - name: db_name
      container:
        name: main
        image: 'argoproj/argosay:v2'
        command:
          - sh
          - '-c'
        args:
          - echo Updating DB {{inputs.parameters.db_name}}

Some Important Details

• The suspended node should have the SAME parameters defined in inputs.parameters and outputs.parameters.
• All the output parameters in the suspended node should have valueFrom.supplied: {}
• The selected values will be available at <SUSPENDED_NODE>.outputs.parameters.<PARAMETER_NAME>

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