CICD Pipelines

Tekton

Tasks

Sequence of steps that are run on the same node. Each step run in its own container.

Pipelines

Tasks with defined order, can execute them in different nodes, links inputs to outputs

PipelineResource

Inputs (e.g. git repository) and outputs (e.g. image registry) to and out of a pipeline or task

TaskRun

The execution and result of running an instance of task

PipelineRun

The execution and result of running an instance of pipeline, which includes a number of TaskRuns

OpenShift Pipelines

  • CI/CD pipeline definition based on Tekton

  • Build images with tools such as S2I, Buildah, Buildpacks, Kaniko, etc

  • Deploy applications to multiple platforms such as Kubernetes, serverless and VMs

Deploy Sample Application

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

You should be able to see the deployment in the OpenShift Web Console by switching over to the Developer perspective of the OpenShift web console. Change from Administrator to Developer from the drop down as shown below:

![Developer Perspective](images/developer.png)

Make sure you are on the pipelines-tutorial project by selecting it from the Project dropdown menu. Either search for pipelines-tutorial in the search bar or scroll down until you find pipelines-tutorial and click on the name of your project.

![Projects](images/projects.png)

On the Topology view of the Developer perspective, you will be able to see the resources you just created.

![Projects](images/petclinic-deployed-1.png)

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. As mentioned previously, tasks can receive inputs (e.g. a git repository) and produce outputs (e.g. an image in a registry).

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](https://github.com/tektoncd/catalog) and [OpenShift Catalog](https://github.com/openshift/pipelines-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/openshift/tektoncd-catalog/release-v0.7/openshift-client/openshift-client-task.yaml
$ oc create -f https://raw.githubusercontent.com/openshift/pipelines-catalog/release-v0.7/s2i-java-8/s2i-java-8-task.yaml

You can take a look at the tasks you created using the [Tekton CLI](https://github.com/tektoncd/cli/releases):

$ 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 the PetClinic application from GitHub and then builds and deploys it on OpenShift using [Source-to-Image (S2I)](https://docs.openshift.com/container-platform/4.1/builds/understanding-image-builds.html#build-strategy-s2i_understanding-image-builds).

<p align="center"><img src="images/pipeline-diagram.svg" width="700" alt="Pipeline Diagram" /></div>

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: 1. Clones the source code of the application from a git repository (app-git resource) 2. Builds the container image using the s2i-java-8 task that generates a Dockerfile for the application and uses [Buildah](https://buildah.io/) to build the image 3. The application image is pushed to an image registry (app-image resource) 4. 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 or the image registry it will be pushed to. That’s because pipeline 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 PipelineResources. 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 task 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/pipeline/01-build-deploy.yaml

Alternatively, in the OpenShift web console, you can click on the + at the top right of the screen while you are in the pipelines-tutorial project:

![OpenShift Console - Import Yaml 1](images/console-import-yaml-1.png)

Paste the YAML into the text editor and click on Create:

![OpenShift Console - Import Yaml 2](images/console-import-yaml-2.png)

Upon creating the pipeline via the web console, you will be taken to a Pipeline Details page that gives an overview of the pipeline you created:

![OpenShift Console - Pipeline Details](images/pipeline-details.png)

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.

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 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 image 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/pipeline/02-resources.yaml

You can see the list of resources created using tkn:

$ 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 tkn:

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

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

Note: OpenShift Pipelines 0.7 does not automatically use the pipeline service account for running pipelineruns. This has been fixed in the next release (OpenShift Pipelines 0.8), but if you want to use the OpenShift web console developer perspective to start the pipeline with OpenShift Pipelines 0.7, run the following commands to elevate the permissions of the default service account, which is currently used by default for running pipelineruns that are started by the OpenShift Console: ` $ oc adm policy add-role-to-user edit -z default `

As soon as you start the petclinic-deploy-pipeline pipeline, a pipelinerun will be instantiated and pods will be 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

After a few minutes, the pipeline should finish successfully.

$ tkn pipeline list

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

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

![PetClinic Deployed](images/petclinic-deployed-2.png)

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

tkn pipeline start petclinic-deploy-pipeline --last