Argo 工作流中的动态“扇入”

Question

Argo permits the dynamic generation of parallel workflow steps based on outputs from previous steps.

An example of this dynamic workflow generation is provided here: https://github.com/argoproj/argo/blob/master/examples/loops-param-result.yaml

I'm trying to create a similar workflow with a final 'fan-in' step that will read outputs from the dynamically created parallel steps. Here's a stab at it:

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: loops-param-result-
spec:
  entrypoint: loop-param-result-example
  templates:
  - name: loop-param-result-example
    steps:
    - - name: generate
        template: gen-number-list
    - - name: write
        template: output-number
        arguments:
          parameters:
          - name: number
            value: "{{item}}"
        withParam: "{{steps.generate.outputs.result}}"
    - - name: fan-in
        template: fan-in
        arguments:
          parameters:
          - name: numbers
            value: "{{steps.write.outputs.parameters.number}}"

  - name: gen-number-list
    script:
      image: python:alpine3.6
      command: [python]
      source: |
        import json
        import sys
        json.dump([i for i in range(20, 31)], sys.stdout)

  - name: output-number
    inputs:
      parameters:
      - name: number
    container:
      image: alpine:latest
      command: [sh, -c]
      args: ["echo {{inputs.parameters.number}} > /tmp/number.txt"]
    outputs:
      parameters:
        - name: number
          valueFrom:
            path: /tmp/number.txt

  - name: fan-in
    inputs:
      parameters:
        - name: numbers
    container:
      image: alpine:latest
      command: [sh, -c]
      args: ["echo received {{inputs.parameters.numbers}}"]

I'm able to submit this workflow, and it runs successfully. Unfortunately, the output of the final fan-in step looks like this:

fan-in: received {{steps.write.outputs.parameters.number}}

The value for the input numbers parameter is not being interpolated. Any ideas about how to get this working?

Answer 1

Aggregated step output parameters are accessible via steps.STEP-NAME.outputs.parameters . It's not possible to access an aggregated set of outputs for one parameter by name.

This slight change to your workflow should get you what you need:

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: loops-param-result-
spec:
  entrypoint: loop-param-result-example
  templates:
  - name: loop-param-result-example
    steps:
    - - name: generate
        template: gen-number-list
    - - name: write
        template: output-number
        arguments:
          parameters:
          - name: number
            value: "{{item}}"
        withParam: "{{steps.generate.outputs.result}}"
    - - name: fan-in
        template: fan-in
        arguments:
          parameters:
          - name: numbers
            value: "{{steps.write.outputs.parameters}}"

  - name: gen-number-list
    script:
      image: python:alpine3.6
      command: [python]
      source: |
        import json
        import sys
        json.dump([i for i in range(20, 31)], sys.stdout)

  - name: output-number
    inputs:
      parameters:
      - name: number
    container:
      image: alpine:latest
      command: [sh, -c]
      args: ["echo {{inputs.parameters.number}} > /tmp/number.txt"]
    outputs:
      parameters:
        - name: number
          valueFrom:
            path: /tmp/number.txt

  - name: fan-in
    inputs:
      parameters:
        - name: numbers
    container:
      image: alpine:latest
      command: [sh, -c]
      args: ["echo received {{inputs.parameters.numbers}}"]

The only change was to remove .number from {{steps.write.outputs.parameters.number}} .

This is the new output:

received [{number:20},{number:21},{number:22},{number:23},{number:24},{number:25},{number:26},{number:27},{number:28},{number:29},{number:30}]

Here is the GitHub issue where output parameter aggregation was discussed/created .

I've put in an enhancement proposal for accessing aggregated output parameters by name.