A simple demonstration of passing information between tasks in Tekton (OpenShift Pipelines)

This document demonstrates passing information from one task to another in a Tekton pipeline. It provides all the steps needed, including YAML files, for a test use case demonstrating a simple way of passing information from one task to another in a Tekton pipeline. It starts from the basics, like creating a project and persistent volume creation (PVC), before building the task and pipeline. Finally, it includes the YAML files for the respective task and pipeline runs. You can extend this example for your own use cases.

I tested this example with Red Hat OpenShift Pipelines version 1.70 and higher, running on OpenShift Version 4.10 and higher. Confirm that the Red Hat OpenShift Pipelines operator is installed.

Create a test project

kind: Project
apiVersion: project.openshift.io/v1
metadata:
  name: test

Before you create tasks and pipeline, confirm that you have a PVC associated with the project where you are creating them.

Create a PVC named test

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: test
  namespace: test
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
  storageClassName: gp2
  volumeMode: Filesystem

In the first task, add a workspace like the one in this spec. Use the workspace name source in this case to use in the second task. Capture what you need to pass in data as results and redirect that information to a file. For example, ee_data.json, which you call in the second task.

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: task1
spec:
  description: >-
    Add execution environment to automation controller
  workspaces:
    - name: source
      results:
        - name: data
          description: ID to be passed to next task
  steps:
    - name: task1
      image: quay.io/rshah/jq
      workingDir: $(workspaces.source.path)
      resources: {}
      script: |
        #!/usr/bin/env bash
        data="This is the output from task 1"
        printf "%s" "${data}" > ee_data.json
        AC_EE_ID=$(cat ee_data.json)
        printf "%s" ${AC_EE_ID}

In task 2, you can reference ee_data.json as shown below:

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: task2
spec:
  workspaces:
    - name: source
  steps:
    - name: task2
      image: quay.io/rshah/jq
      workingDir: $(workspaces.source.path)
      resources: {}
      script: |
        #!/usr/bin/env bash
        AC_EE_ID=$(cat ee_data.json)
        printf "%s" ${AC_EE_ID}

When you run task1 and task2 in a pipeline, both tasks should print the same output.

Create a pipeline

apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: "value_pass_pipeline"
spec:
  workspaces:
    - name: source
  params:
    - description: Verify the TLS on the registry endpoint (for push/pull to a non-TLS registry)
      name: TLSVERIFY
      type: string
      default: "false"
    - description: Dummy parameter for task1
      name: task1
      type: string
      default: "task1"
    - description: Dummy parameter for task2
      name: task2
      type: string
      default: "task2"
  tasks:
    - name: task1
      taskRef:
        kind: Task
        name: task1
      params:
        workspaces:
          - name: source
            workspace: source
    - name: task2
      taskRef:
        kind: Task
        name: task2
      params:
        runAfter:
          - task1
        workspaces:
          - name: source
            workspace: source

When you run the pipeline, both tasks will show the output shown below:

STEP-TASK1 This is the output from task 1
STEP-TASK2 This is the output from task 1

Task and pipeline runs

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: test-0ij91k-task1
  namespace: test
spec:
  resources: {}
  serviceAccountName: pipeline
  taskRef:
    kind: Task
    name: task1
  timeout: 59m59.989014151s
  workspaces:
    - name: source
      persistentVolumeClaim:
        claimName: test
---
apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: test-0ij91k-task2
  namespace: test
spec:
  resources: {}
  serviceAccountName: pipeline
  taskRef:
    kind: Task
    name: task2
  timeout: 59m59.989014151s
  workspaces:
    - name: source
      persistentVolumeClaim:
        claimName: test
---
apiVersion: tekton.dev/v1beta1
kind: PipelineRun
metadata:
  name: test-0ij91k
  namespace: test
spec:
  pipelineRef:
    name: test
  serviceAccountName: pipeline
  timeout: 1h0m0s
  workspaces:
    - name: source
      persistentVolumeClaim:
        claimName: test

This simple example provides a basic understanding of passing output from one task as input to another. You can extend this to your use cases.