Pipeline is one of the core building blocks in designing a CI/CD use case on Kubernetes with Tekton. A Tekton Pipeline is a collection of tasks, which run based on how they are arranged. These tasks can be represented as a graph in which each node represents a task and can be arranged in many different ways.

• Run all tasks (task-A, task-B, and task-C) in parallel. The three tasks start running independently and finish irrespective of the success or failure of other tasks. This kind of arrangement applies to a CI/CD use case, such as running unit tests and integration tests in parallel.

  tasks:
    - name: task-A
      taskRef:
        name: task1
    - name: task-B
      taskRef:
        name: task2
    - name: task-C
      taskRef:
        name: task3

• Show more

• Design sequence of tasks that run one after each other by using runAfter. For example, PipelineRun instantiates build-image and waits for it to finish. If build-image exits with success, PipelineRun instantiates e2e-tests, otherwise PipelineRun exits with failure without running the rest of the tasks. The same process applies to the next task. This example is the ideal arrangement, but hardly works in real world. It’s very common to run into task failures and require further processing if such failures.

  tasks:
    - name: build-image
      taskRef:
        name: build-image
    - name: e2e-tests
      runAfter: [ build-image ]
      taskRef:
        name: e2e-tests
    - name: deploy
      runAfter: [ e2e-tests ]
      taskRef:
        name: deploy

• Show more

• Design failure strategies by using finally. PipelineRun runs tasks that are specified under the finally section after all tasks under tasks section are completed regardless success or failure. For example, finally tasks start running after all tasks are completed successfully or one of the tasks exits with failure. finally tasks run in parallel just before they exit the PipelineRun. The PipelineRun exit status contains TaskRuns for all tasks, including the finally tasks.

  tasks:
    - name: build-image
      taskRef:
        name: build-image
    - name: e2e-tests
      runAfter: [ build-image ]
      taskRef:
        name: e2e-tests
    - name: deploy
      runAfter: [ e2e-tests ]
      taskRef:
        name: deploy
  finally:
    - name: cleanup
      taskRef:
        name: cleanup

• Show more

So far, this looks great, but what about running a check before you run a task? You can design PipelineRun to include conditional tasks by using the Condition CRD to run a check before you run that task. The Condition CRD, just like a task, creates a new pod in a Kubernetes cluster to run that check. Depending on the outcome of that Condition CRD, a task is run or declared a failure with a conditionCheckFailed.

#devops #tekton