How to pass parameters in nested argo steps? - argo-workflows

Question

I am trying to pass parameters from an outer step template to an inner step template in argo. Below is my workflow definition.
apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
generateName: fanout-
spec:
templates:
- name: process-workflows
steps:
- - name: fanout
template: fan-out
- - name: fanout-step
template: parallel-process
arguments:
parameters:
- name: batch
value: '{{item}}'
withParam: '{{steps.fanout.outputs.result}}'
- name: fan-out
script:
name: main
image: 'node:lts-alpine3.14'
command:
- node
resources: {}
source: |
inputlist = JSON.parse({{=toJson(workflow.parameters.inputlist)}})
fanout = {{workflow.parameters.fanout}}
var i,j, result=[];
for (i = 0,j = inputlist.length; i < j; i += fanout) {
result.push(inputlist.slice(i, i + fanout));
}
console.log(JSON.stringify(result))
- name: parallel-process
inputs:
parameters:
- name: batch
steps:
- - name: actualprocessor
template: process
arguments:
parameters:
- name: input
value: {{inputs.parameters.batch}}
- - name: aggregate-result
template: aggregate
arguments:
parameters:
- name: aggregate
value: {{steps.actualprocessor.outputs.parameters.res}}
- name: process
inputs:
parameters:
- name: input
outputs:
parameters:
- name: res
valueFrom:
path: /tmp/res.txt
script:
name: main
image: 'alpine:latest'
command:
- sh
source: |
sleep 5
echo 'awakened...'
echo processing-{{=toJson(inputs.parameters.input)}}
echo {{=toJson(inputs.parameters.input)}} > /tmp/res.txt
- name: aggregate
inputs:
parameters:
- name: aggregate
container:
name: main
image: 'alpine:latest'
command:
- sh
- '-c'
args:
- 'echo received {{inputs.parameters.aggregate}}'
entrypoint: process-workflows
arguments:
parameters:
- name: inputlist
value: |
[
{"k" : "v1", "a" : [{ "k": true}]},
{"k" : "v2", "a" : [{ "k": true}]}
]
- name: fanout
value: '1'
Use case:
The fanout-step step (outer step) uses parallel-process template (inner step). It provides a batch argument to the parallel-process template. The parallel-process template needs to provide the value of batch to the input parameters in the target step.
Issue: The input parameter inside the actualprocessor step is empty. I can see that the batch input param is getting populated correctly.
What am I missing here?

Answer 1

The issue is resolved by encasing the parameters in quotes. Thanks to Tom Slabbaer for pointing it out.
Below is the working template.
apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
generateName: fanout-
spec:
templates:
- name: process-workflows
steps:
- - name: fanout
template: fan-out
- - name: fanout-step
template: parallel-process
arguments:
parameters:
- name: batch
value: '{{item}}'
withParam: '{{steps.fanout.outputs.result}}'
- name: fan-out
script:
name: main
image: 'node:lts-alpine3.14'
command:
- node
resources: {}
source: |
inputlist = JSON.parse({{=toJson(workflow.parameters.inputlist)}})
fanout = {{workflow.parameters.fanout}}
var i,j, result=[];
for (i = 0,j = inputlist.length; i < j; i += fanout) {
result.push(inputlist.slice(i, i + fanout));
}
console.log(JSON.stringify(result))
- name: parallel-process
inputs:
parameters:
- name: batch
steps:
- - name: actualprocessor
template: process
arguments:
parameters:
- name: input
value: "{{inputs.parameters.batch}}"
- - name: aggregate-result
template: aggregate
arguments:
parameters:
- name: aggregate
value: "{{steps.actualprocessor.outputs.parameters.res}}"
- name: process
inputs:
parameters:
- name: input
outputs:
parameters:
- name: res
valueFrom:
path: /tmp/res.txt
script:
name: main
image: 'alpine:latest'
command:
- sh
source: |
sleep 5
echo 'awakened...'
echo processing-{{=toJson(inputs.parameters.input)}}
echo {{=toJson(inputs.parameters.input)}} > /tmp/res.txt
- name: aggregate
inputs:
parameters:
- name: aggregate
container:
name: main
image: 'alpine:latest'
command:
- sh
- '-c'
args:
- 'echo received {{inputs.parameters.aggregate}}'
entrypoint: process-workflows
arguments:
parameters:
- name: inputlist
value: |
[
{"k" : "v1", "a" : [{ "k": true}]},
{"k" : "v2", "a" : [{ "k": true}]}
]
- name: fanout
value: '1'