OpenShift Pipelines Tutorial

Welcome to the OpenShift Pipelines tutorial!

OpenShift Pipelines is a cloud-native, continuous integration and delivery (CI/CD) solution for building pipelines using Tekton. Tekton is a flexible, Kubernetes-native, open-source CI/CD framework that enables automating deployments across multiple platforms (Kubernetes, serverless, VMs, etc) by abstracting away the underlying details.

OpenShift Pipelines features:

Standard CI/CD pipeline definition based on Tekton
Build images with Kubernetes tools such as S2I, Buildah, Buildpacks, Kaniko, etc
Deploy applications to multiple platforms such as Kubernetes, serverless and VMs
Easy to extend and integrate with existing tools
Scale pipelines on-demand
Portable across any Kubernetes platform
Designed for microservices and decentralized teams
Integrated with the OpenShift Developer Console

This tutorial walks you through pipeline concepts and how to create and run a simple pipeline for building and deploying a containerized app on OpenShift.

In this tutorial you will:

Learn about Tekton concepts
Install OpenShift Pipelines
Deploy a Sample Application
Install Tasks
Create a Pipeline
Trigger a Pipeline

Prerequisite

You need an OpenShift 4 cluster in order to complete this tutorial. If you don't have an existing cluster, go to http://try.openshift.com and register for free in order to get an OpenShift 4 cluster up and running on AWS within minutes.

You will also use the Tekton CLI (tkn) through out this tutorial. Download the Tekton CLI and copy it to a location on your PATH.

Concepts

Tekton defines a number of Kubernetes custom resources as building blocks in order to standardize pipeline concepts and provide a terminology that is consistent across CI/CD solutions. These custom resources (CR) are an extension of Kubernetes that let users create and interact with these objects using kubectl and other Kubernetes tools.

The custom resources needed to define a pipeline are:

Task: a reusable, loosely coupled number of steps that perform a specific task (e.g., building a container image)
Pipeline: the definition of the pipeline and the Tasks that it should perform
PipelineResource: inputs (e.g., git repository) and outputs (e.g., image registry) to and out of a pipeline or task
TaskRun: the result of running an instance of task
PipelineRun: the result of running an instance of pipeline, which includes a number of TaskRuns

In short, in order to create a pipeline, one does the following:

Create custom or install existing reusable Tasks
Create a Pipeline and PipelineResources to define your application's delivery pipeline
Create a PipelineRun to instantiate and invoke the pipeline

For further details on pipeline concepts, refer to the Tekton documentation that provides an excellent guide for understanding various parameters and attributes available for defining pipelines.

In the following sections, you will go through each of the above steps to define and invoke a pipeline.

Install OpenShift Pipelines

OpenShift Pipelines is provided as an add-on on top of OpenShift that can be installed via an operator available in the OpenShift OperatorHub. Follow these instructions in order to install OpenShift Pipelines on OpenShift via the OperatorHub.

Deploy Sample Application

Create a project for the sample application that you will be using in this tutorial:

$ oc new-project pipelines-tutorial

Building container images using build tools such as S2I, Buildah, Kaniko, etc require privileged access to the cluster. OpenShift default security settings do not allow privileged containers unless specifically configured. Create a service account for running pipelines and enable it to run privileged pods for building images:

$ oc create serviceaccount pipeline
$ oc adm policy add-scc-to-user privileged -z pipeline
$ oc adm policy add-role-to-user edit -z pipeline

You will use the Spring PetClinic sample application during this tutorial, which is a simple Spring Boot application.

Create the Kubernetes objects for deploying the PetClinic app on OpenShift. The deployment will not complete since there are no container images built for the PetClinic application yet. That you will do in the following sections through a CI/CD pipeline:

$ oc create -f https://raw.githubusercontent.com/openshift/pipelines-tutorial/master/resources/petclinic.yaml

You should be able to see the deployment in the OpenShift Web Console.

Install Tasks

Tasks consist of a number of steps that are executed sequentially. Each task is executed in a separate container within the same pod. They can also have inputs and outputs in order to interact with other tasks in the pipeline.

Here is an example of a Maven task for building a Maven-based Java application:

apiVersion: tekton.dev/v1alpha1
kind: Task
metadata:
  name: maven-build
spec:
  inputs:
    resources:
    - name: workspace-git
      targetPath: /
      type: git
  steps:
  - name: build
    image: maven:3.6.0-jdk-8-slim
    command:
    - /usr/bin/mvn
    args:
    - install

When a task starts running, it starts a pod and runs each step sequentially in a separate container on the same pod. This task happens to have a single step, but tasks can have multiple steps, and, since they run within the same pod, they have access to the same volumes in order to cache files, access configmaps, secrets, etc. Tasks can also receive inputs (e.g., a git repository) and outputs (e.g., an image in a registry) in order to interact with each other.

Note that only the requirement for a git repository is declared on the task and not a specific git repository to be used. That allows tasks to be reusable for multiple pipelines and purposes. You can find more examples of reusable tasks in the Tekton Catalog and OpenShift Catalog repositories.

Install the openshift-client and s2i-java tasks from the catalog repository using oc or kubectl, which you will need for creating a pipeline in the next section:

$ oc create -f https://raw.githubusercontent.com/tektoncd/catalog/master/openshift-client/openshift-client-task.yaml
$ oc create -f https://raw.githubusercontent.com/openshift/pipelines-catalog/master/s2i-java-8/s2i-java-8-task.yaml

You can take a look at the list of install tasks using the Tekton CLI:

$ tkn task ls

NAME               AGE
openshift-client   58 seconds ago
s2i-java-8         1 minute ago

Create Pipeline

A pipeline defines a number of tasks that should be executed and how they interact with each other via their inputs and outputs.

In this tutorial, you will create a pipeline that takes the source code of PetClinic application from GitHub and then builds and deploys it on OpenShift using Source-to-Image (S2I).

Here is the YAML file that represents the above pipeline:

apiVersion: tekton.dev/v1alpha1
kind: Pipeline
metadata:
  name: petclinic-deploy-pipeline
spec:
  resources:
  - name: app-git
    type: git
  - name: app-image
    type: image
  tasks:
  - name: build
    taskRef:
      name: s2i-java-8
    params:
      - name: TLSVERIFY
        value: "false"
    resources:
      inputs:
      - name: source
        resource: app-git
      outputs:
      - name: image
        resource: app-image
  - name: deploy
    taskRef:
      name: openshift-client
    runAfter:
      - build
    params:
    - name: ARGS
      value: "rollout latest spring-petclinic"

This pipeline performs the following:

Clones the source code of the application from a Git repository (app-git resource)
Builds the container image using the s2i-java-8 task that generates a Dockerfile for the application and uses Buildah to build the image
The application image is pushed to an image registry (app-image resource)
The new application image is deployed on OpenShift using the openshift-cli

You might have noticed that there are no references to the PetClinic Git repository and its image in the registry. That's because Pipelines in Tekton are designed to be generic and re-usable across environments and stages through the application's lifecycle. Pipelines abstract away the specifics of the Git source repository and image to be produced as resources. When triggering a pipeline, you can provide different Git repositories and image registries to be used during pipeline execution. Be patient! You will do that in a little bit in the next section.

The execution order of tasks is determined by dependencies that are defined between the tasks via inputs and outputs as well as explicit orders that are defined via runAfter.

Create the pipeline by running the following:

$ oc create -f https://raw.githubusercontent.com/openshift/pipelines-tutorial/master/resources/petclinic-deploy-pipeline.yaml

Alternatively, in the OpenShift web console, you can click on Add → Import YAML at the top right of the screen while you are in the pipelines-tutorial project, paste the YAML into the textfield, and click on Create.

Check the list of pipelines you have created using the CLI:

$ tkn pipeline ls

NAME                       AGE              LAST RUN   STARTED   DURATION   STATUS
petclinic-deploy-pipeline  25 seconds ago   ---        ---       ---        ---

Trigger Pipeline

Now that the pipeline is created, you can trigger it to execute the tasks specified in the pipeline. Triggering pipelines is an area that is under development and in the next release it will be possible to be done via the OpenShift web console and Tekton CLI. In this tutorial, you will trigger the pipeline through creating the Kubernetes objects (the hard way!) in order to learn the mechanics of triggering.

First, you should create a number of PipelineResources that contain the specifics of the Git repository and image registry to be used in the pipeline during execution. Expectedly, these are also reusable across multiple pipelines.

The following PipelineResource defines the Git repository and reference for the PetClinic application:

apiVersion: tekton.dev/v1alpha1
kind: PipelineResource
metadata:
  name: petclinic-git
spec:
  type: git
  params:
  - name: url
    value: https://github.com/spring-projects/spring-petclinic

And the following defines the OpenShift internal registry for the PetClinic image to be pushed to:

apiVersion: tekton.dev/v1alpha1
kind: PipelineResource
metadata:
  name: petclinic-image
spec:
  type: image
  params:
  - name: url
    value: image-registry.openshift-image-registry.svc:5000/pipelines-tutorial/spring-petclinic

Create the above pipeline resources via the OpenShift web console or by running the following:

$ oc create -f https://raw.githubusercontent.com/openshift/pipelines-tutorial/master/resources/petclinic-resources.yaml

You can see the list of resources created using the CLI:

$ tkn resource ls

NAME              TYPE    DETAILS
petclinic-git     git     url: https://github.com/spring-projects/spring-petclinic
petclinic-image   image   url: image-registry.openshift-image-registry.svc:5000/pipelines-tutorial/spring-petclinic

A PipelineRun is how you can start a pipeline and tie it to the Git and image resources that should be used for this specific invocation. You can start the pipeline using the CLI:

$ tkn pipeline start petclinic-deploy-pipeline \
        -r app-git=petclinic-git \
        -r app-image=petclinic-image \
        -s pipeline

Pipelinerun started: petclinic-deploy-pipeline-run-q62p8

The -r flag specifies the PipelineResources that should be provided to the pipeline and the -s flag specifies the service account to be used for running the pipeline.

As soon as you started the petclinic-deploy-pipeline pipeline, a pipelinerun is instantiated and pods are created to execute the tasks that are defined in the pipeline.

$ tkn pipeline list
NAME                        AGE             LAST RUN                              STARTED         DURATION   STATUS
petclinic-deploy-pipeline   23 seconds ago   petclinic-deploy-pipeline-run-tsv92  23 seconds ago   ---        Running

Check out the logs of the pipelinerun as it runs using the tkn pipeline logs command which interactively allows you to pick the pipelinerun of your interest and inspect the logs:

$ tkn pipeline logs -f                                                                                             
? Select pipeline : petclinic-deploy-pipeline
? Select pipelinerun : petclinic-deploy-pipeline-run-tsv92 started 39 seconds ago

...
[build : nop] Build successful
[deploy : build-step-oc] deploymentconfig.apps.openshift.io/spring-petclinic rolled out
[deploy : nop] Build successful

After a few minutes, the pipeline would finish successfully.

$ tkn pipeline list 

NAME                        AGE             LAST RUN                              STARTED         DURATION    STATUS
petclinic-deploy-pipeline   7 minutes ago   petclinic-deploy-pipeline-run-tsv92   5 minutes ago   4 minutes   Succeeded

Looking back at the project, you should see that the PetClinic image is successfully built and deployed.

If you want to re-run the pipeline again, you can use the following short-hand command to rerun the last pipelinerun again, using the same pipeline resources and service account used in the previous pipeline:

tkn pipeline start petclinic-deploy-pipeline --last

dischord01 / pipelines-tutorial