Hands-On Tekton

Requirements

Minikube -OR- Katacoda Kubernetes Playground
tkn
(Optional) VS Code Tekton extension

Intro

Intros, why should you care about CI/CD
What is CI/CD and Cloud-Native CI/CD
Tekton

Installation

First, make sure you've installed tkn in your environment, whether you are using Minikube on your local machine or the Kubernetes playground. If you're using the Kubernetes playground, enter commands in the top terminal labeled Terminal Host 1.

Then, install Tekton on your cluster.

kubectl apply --filename https://storage.googleapis.com/tekton-releases/pipeline/latest/release.yaml

Finally, clone this repository and cd into the handson-tekton directory.

git clone https://github.com/joellord/handson-tekton
cd handson-tekton

Create a Hello World task

Tasks happen inside a pod. You can use tasks to perform various CI/CD operations. Things like compiling your application or running some unit tests.

For this first Task, you will simply use a Red Hat Universal Base Image and echo a hello world.

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: hello
spec:
  steps:
    - name: say-hello
      image: registry.access.redhat.com/ubi8/ubi
      command:
        - /bin/bash
      args: ['-c', 'echo Hello World']

Apply this Task to your cluster just like any other Kubernetes object. Then run it using tkn, the CLI tool for Tekton.

kubectl apply -f ./demo/01-hello.yaml
tkn task start --showlog hello

Add a Parameter to the Task

Tasks can also take parameters. This way, you can pass various flags to be used in this Task. These parameters can be instrumental in making your Tasks more generic and reusable across Pipelines.

In this next example, you will create a task that will ask for a person's name and then say Hello to that person.

Starting with the previous example, you can add a params property to your task's spec. A param takes a name and a type. You can also add a description and a default value for this Task.

For this parameter, the name is person, the description is Name of person to greet, the default value is World, and the type of parameter is a string. If you don't provide a parameter to this Task, the greeting will be "Hello World".

You can then access those params by using variable substitution. In this case, change the word "World" in the args line to $(params.person).

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: hello
spec:
  params:
    - name: person
      description: Name of person to greet
      default: World
      type: string
  steps:
    - name: say-hello
      image: registry.access.redhat.com/ubi8/ubi
      command:
        - /bin/bash
      args: ['-c', 'echo Hello $(params.person)']

Apply this new Task to your cluster with kubectl and then rerun it. You will now be asked for the name of the person to greet.

You can also specify the parameters directly from the command line by using the -p argument.

kubectl apply -f ./demo/02-param.yaml
tkn task start --showlog hello
tkn task start --showlog -p person=Joel hello

Multiple steps to Task

Your tasks can have more than one step. In this next example, you will change this Task to use two steps. The first one will write to a file, and the second one will output the content of that file. The steps will run in the order in which they are defined in the steps array.

First, start by adding a new step called write-hello. In here, you will use the same UBI base image. Instead of using a single command, you can also write a script. You can do this with a script parameter, followed by a | and the actual script to run. In this script, start by echoing "Preparing greeting", then echo the "Hello $(params.person)" that you had in the previous example into the ~/hello.txt file. Finally, add a little pause with the sleep command and echo "Done".

For the second step, you can create a new step called say-hello. This second step will run in its container but share the /tekton folder from the previous step. In the first step, you created a file in the "~" folder, which maps to "/tekton/home". For this second step, you can use an image node:14, and the file you created in the first step will be accessible. You can also run a NodeJS script as long as you specify the executable in the #! line of your script. In this case, you can write a script that will output the content of the ~/hello.txt file.

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: hello
spec:
  params:
    - name: person
      description: Name of person to greet
      default: World
      type: string
  steps:
    - name: write-hello
      image: registry.access.redhat.com/ubi8/ubi
      script: |
        #!/usr/bin/env bash
        echo Preparing greeting
        echo Hello $(params.person) > /tekton/home/hello.txt
        sleep 2
        echo Done!
    - name: say-hello
      image: node:14
      script: |
        #!/usr/bin/env node
        let fs = require("fs");
        let file = "/tekton/home/hello.txt";
        let fileContent = fs.readFileSync(file).toString();
        console.log(fileContent);

You can now apply this Task to your cluster and run this Task with tkn. You will see that you can easily see each step's output as the logs outputs in various colours.

kubectl apply -f ./demo/03-multistep.yaml
tkn task start --showlog hello

Pipelines

Tasks are useful, but you will usually want to run more than one Task. In fact, tasks should do one single thing so you can reuse them across pipelines or even within a single pipeline. For this next example, you will start by writing a generic task that will echo whatever it receives in the parameters.

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: say-something
spec:
  params:
    - name: say-what
      description: What should I say
      default: hello
      type: string
    - name: pause-duration
      description: How long to wait before saying something
      default: "0"
      type: string
  steps:
    - name: say-it
      image: registry.access.redhat.com/ubi8/ubi
      command:
        - /bin/bash
      args: ['-c', 'sleep $(params.pause-duration) && echo $(params.say-what)']

You are now ready to build your first Pipeline. A pipeline is a series of tasks that can run either in parallel or sequentially. In this Pipeline, you will use the say-something tasks twice with different outputs.

apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: say-things
spec:
  tasks:
    - name: first-task
      params:
        - name: pause-duration
          value: "2"
        - name: say-what
          value: "Hello, this is the first task"
      taskRef:
        name: say-something
    - name: second-task
      params:
        - name: say-what
          value: "And this is the second task"
      taskRef:
        name: say-something

You can now apply the Task and this new Pipeline to your cluster and start the Pipeline. Using tkn pipeline start will create a PipelineRun with a random name. You can also see the logs of the Pipeline by using the --showlog parameter.

kubectl apply -f ./demo/04-tasks.yaml
kubectl apply -f ./demo/05-pipeline.yaml
tkn pipeline start say-things --showlog

Run in parallel or sequentially

You might have noticed that in the last example, the tasks' output came out in the wrong order. That is because Tekton will try to start all the tasks simultaneously so they can run in parallel. If you needed a task to complete before another one, you could use the runAfter parameter in the task definition of your Pipeline.

apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: say-things-in-order
spec:
  tasks:
    - name: first-task
      params:
        - name: pause-duration
          value: "2"
        - name: say-what
          value: "Hello, this is the first task"
      taskRef:
        name: say-something
    - name: second-task
      params:
        - name: say-what
          value: "Happening after task 1, in parallel with task 3"
        - name: pause-duration
          value: "2"
      taskRef:
        name: say-something
      runAfter:
        - first-task
    - name: third-task
      params:
        - name: say-what
          value: "Happening after task 1, in parallel with task 2"
        - name: pause-duration
          value: "1"
      taskRef:
        name: say-something
      runAfter:
        - first-task
    - name: fourth-task
      params:
        - name: say-what
          value: "Happening after task 2 and 3"
      taskRef:
        name: say-something
      runAfter:
        - second-task
        - third-task

If you apply this new Pipeline and run it with the Tekton CLI tool, you should see the logs from each Task, and you should see them in order. If you've installed the Tekton VS Code extension by Red Hat, you will also be able to see a preview of your Pipeline and see the order in which each of the steps is happening.

kubectl apply -f ./demo/06-pipeline-order.yaml
tkn pipeline start say-things-in-order --showlog

Resources

The last object that will be demonstrated in this lab is PipelineResources. When you create pipelines, you will want to make them as generic as you can. This way, your pipelines can be reused across various projects. In the previous examples, we used pipelines that didn't do anything interesting. Typically, you will want to have some input on which you will want to perform your tasks. Usually, this would be a git repository. At the end of your Pipeline, you will also typically want some sort of output. Something like an image. This is where PipelineResources will come into play.

In this next example, you will create a pipeline that will take any git repository as a PipelineResource and then count the number of files.

First, you can start by creating a task. This Task will be similar to the ones you've created earlier but will also have an input resource.

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: count-files
spec:
  resources:
    inputs:
      - name: repo
        type: git
        targetPath: code
  steps:
    - name: count
      image: registry.access.redhat.com/ubi8/ubi
      workingDir: /workspace
      command:
        - /bin/bash
      args: ['-c', 'echo $(find ./code -type f | wc -l) files in repo']

Next, you can create a pipeline that will also have an input resource. This Pipeline will have a single task, which will be the count-files task you've just defined.

apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: count
spec:
  resources:
    - name: git-repo
      type: git
  tasks:
    - name: count-task
      taskRef:
        name: count-files
      resources:
        inputs:
          - name: repo
            resource: git-repo

Finally, you can create a PipelineResource. This resource is of type git, and you can put in the link of a Github repository in the url parameter. You can use the repo for this project.

apiVersion: tekton.dev/v1alpha1
kind: PipelineResource
metadata:
  name: git-repo
spec:
  type: git
  params:
    - name: url
      value: https://github.com/joellord/handson-tekton.git

Once you have all the required pieces, you can apply this file to the cluster again, and start this pipelinerun. When you begin the Pipeline with the CLI, you will be prompted on the git resource to use. You can either use the resource you've just created or create your own. You could also use the --resource parameter with the CLI to specify which resources to use.

kubectl apply -f ./demo/07-pipelineresource.yaml
tkn pipeline start count --showlog
tkn pipeline start count --showlog --resource git-repo=git-repo

Workspaces

It is important to note that PipelineResources is still in alpha. The Tekton core team questions whether they should stay in the spec or not. In the latest version of Tekton, workspaces were added to share file systems between various tasks in a Pipeline. You can find an example of a pipeline using a workspace in the file workspace.yaml. Workspaces require the usage of PersistentVolumes and PersistentVolumeClaims, which are out of scope for this lab.

Real-world pipeline

So far, all these examples have been good to demonstrate how Tekton internals work but not very useful for your day to day developer life. Let's look at a real Pipeline. In this section, you will create a Pipeline that will run three tasks for a NodeJS project.

It will run a linter to ensure there are not linting issues in the code
It will run the unit tests to validate the code
If both the linting and testing pass, it will create a NodeJS image and push it to Docker using s2i and buildah.

First, you will start with the npm task. This Task will be generic enough to be used for the first two steps of the Pipeline.

This Task has two parameters, one for the command line arguments to be used with npm (action) and the other one to specify the path of the application inside the git repository.

This Task will also need an input resource of type git. This input is the git repository on which you will apply the npm commands.

You will then need to add two steps to this Task. First, run an npm install to ensure that all the dependencies are there. And then run npm with the action parameter.

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: npm
spec:
  params:
    - name: pathContext
      description: Path to application inside git
      default: "."
      type: string
    - name: action
      description: Operation to be performed by npm
      default: "start"
      type: string
  resources:
    inputs:
      - name: repo
        type: git
  steps:
    - name: npm-install
      image: node:14
      workingDir: /workspace
      command:
        - /bin/bash
      args: ['-c', 'cd repo/$(params.pathContext) && npm install']
    - name: npm-lint
      image: node:14
      workingDir: /workspace
      command:
        - /bin/bash
      args: ['-c', 'cd repo/$(params.pathContext) && npm $(params.action)']

Thanks to this action parameter, you can now reuse this Task for both the npm run test and npm run lint tasks.

Next up will be the s2i-nodejs Task. This Task will use s2i and buildah to generate, build and push an image from the source code that we provide to it.

You will need a few parameters for this Task. First, you will need the username and password for the registry to use. If using Docker Hub, you can generate an API token instead of a password. Then, you need an image name and the registry. The image generated by buildah will have the name <registry>/<user>/<image-name>. You can also add the git input resource.

You can then add the multiple steps required to build and deploy your image. First, you need to generate a Dockerfile with s2i. For more information on how s2i works, you can check out https://github.com/openshift/source-to-image. For this pod, you will mount a volume that can be shared with the other steps. You will add the volumes at the end of this Task's spec property.

Then, you can use buildah to build the image. You will do this in the build step. For more information on buildah, check out the website https://buildah.io/.

And finally, you will use buildah again to push the image to an image registry. Note how the parameters are used in each of the commands to make this Task as generic as possible. This way, it can be reused in different pipelines.

Finally, you will need to describe the two volumes shared between the steps in this Task. The volumes in this example have a type emptyDir, which means they will start as empty directories and simply be destroyed once the Task is completed.

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: s2i-nodejs
spec:
  params:
    - name: user
      type: string
    - name: pass
      type: string
    - name: image-name
      type: string
    - name: registry
      type: string
      default: "docker.io"
  resources:
    inputs:
      - name: repo
        type: git
  steps:
    - name: generate
      image: quay.io/openshift-pipeline/s2i
      workingDir: /workspace/repo/app
      command: ["s2i", "build", ".", "registry.access.redhat.com/ubi8/nodejs-12", "--as-dockerfile", "/gensource/Dockerfile.gen"]
      volumeMounts:
        - name: gensource
          mountPath: /gensource
    - name: build
      image: quay.io/buildah/stable
      workingDir: /gensource
      command: ["buildah", "bud", "--tls-verify=false", "--layers", "-f", "/gensource/Dockerfile.gen", "-t", "$(params.registry)/$(params.user)/$(params.image-name)", "."]
      volumeMounts:
        - name: varlibcontainers
          mountPath: /var/lib/containers
        - name: gensource
          mountPath: /gensource
      securityContext:
        privileged: true
    - name: push
      image: quay.io/buildah/stable
      command: ['buildah', 'push', '--creds=$(params.user):$(params.pass)', '--tls-verify=false', '$(params.registry)/$(params.user)/$(params.image-name)', 'docker://$(params.registry)/$(params.user)/$(params.image-name)']
      volumeMounts:
        - name: varlibcontainers
          mountPath: /var/lib/containers
      securityContext:
        privileged: true
  volumes:
    - name: varlibcontainers
      emptyDir: {}
    - name: gensource
      emptyDir: {}

You are now ready to deploy your application. First, apply this file to your cluster and then start this new Pipeline using the Tekton CLI tool. It will take a little bit more time as it goes through all the steps. Once your Pipeline completed, you can start the application by using docker run. This container will start the NodeJS server on port 3000. The server has a route called /add that will take two parameters and add them together. You can test this out by using a curl command.

kubectl apply -f ./demo/08-realworld.yaml
tkn pipeline start app-deploy --showlog
docker run -d -p 3000:3000 --rm --name handson <user>/<image-name>
curl localhost:3000/add/2/5

More Resources

If you want to keep learning more about Tekton, check out these resources:

https://tekton.dev - The main tekton website
https://hub-preview.tekton.dev - Tekton Hub, where you can find reusable tasks and pipelines
https://developers.redhat.com/topics/ci-cd - Developer-facing info on CI/CD and Tekton

joellord/handson-tekton

joellord

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