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Kubernetes Tekton

Introduction​

Tekton is a powerful, flexible, and Kubernetes-native framework for creating continuous integration and continuous delivery (CI/CD) systems. Developed as part of the CD Foundation (a Linux Foundation project), Tekton provides a set of shared, open-source components for building CI/CD pipelines that can be used across cloud providers and on-premises systems.

Unlike traditional CI/CD tools that run alongside Kubernetes, Tekton is built specifically to leverage Kubernetes' capabilities and runs entirely on a Kubernetes cluster. This native integration allows Tekton to take full advantage of Kubernetes' scaling, resource management, and extensibility features.

Understanding Tekton Core Concepts​

Tekton introduces several custom resources to Kubernetes that form the building blocks of a CI/CD pipeline:

Task​

A Task is the smallest building block in Tekton. It defines a series of steps that run sequentially in a pod to achieve a specific goal, such as compiling code, running tests, or building a container image.

yaml
apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: hello-world
spec:
  steps:
    - name: say-hello
      image: ubuntu
      command:
        - echo
      args:
        - "Hello, Tekton!"

TaskRun​

A TaskRun is an instance of a Task execution. It defines the inputs, outputs, and execution parameters for a Task.

yaml
apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: hello-world-run
spec:
  taskRef:
    name: hello-world

Output:

TaskRun hello-world-run started
Step say-hello completed with output: Hello, Tekton!
TaskRun hello-world-run succeeded

Pipeline​

A Pipeline defines a collection of Tasks that should be executed in a specific order, with defined inputs, outputs, and parameters.

yaml
apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: build-test-deploy
spec:
  tasks:
    - name: build
      taskRef:
        name: build-app
    - name: test
      taskRef:
        name: test-app
      runAfter:
        - build
    - name: deploy
      taskRef:
        name: deploy-app
      runAfter:
        - test

PipelineRun​

A PipelineRun is an instance of Pipeline execution, defining the parameters, resources, and service accounts to use for the Pipeline.

yaml
apiVersion: tekton.dev/v1beta1
kind: PipelineRun
metadata:
  name: build-test-deploy-run
spec:
  pipelineRef:
    name: build-test-deploy

PipelineResource (Deprecated)​

PipelineResource was a concept for defining input and output resources for Tasks and Pipelines. However, it's been deprecated in favor of using parameters and workspaces.

Workspaces​

Workspaces provide a mechanism for Tasks to share data. They can be backed by various volume types such as PersistentVolumeClaims, ConfigMaps, or Secrets.

yaml
apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: task-with-workspace
spec:
  workspaces:
    - name: source-code
  steps:
    - name: list-files
      image: ubuntu
      command: ["ls"]
      args: ["-la", "$(workspaces.source-code.path)"]

Setting Up Tekton​

Let's walk through setting up Tekton on your Kubernetes cluster:

Prerequisites​

  • A running Kubernetes cluster (v1.18 or newer)
  • kubectl installed and configured
  • Cluster admin permissions

Installation Steps​

  1. Install Tekton Pipelines:
bash
kubectl apply -f https://storage.googleapis.com/tekton-releases/pipeline/latest/release.yaml
  1. Verify the installation:
bash
kubectl get pods -n tekton-pipelines

You should see several Tekton controller pods running.

  1. (Optional) Install Tekton Dashboard:
bash
kubectl apply -f https://storage.googleapis.com/tekton-releases/dashboard/latest/release.yaml
  1. (Optional) Install Tekton CLI (tkn):
bash
# For macOS
brew tap tektoncd/tools
brew install tektoncd/tools/tektoncd-cli

# For Linux
curl -LO https://github.com/tektoncd/cli/releases/download/v0.30.0/tkn_0.30.0_Linux_x86_64.tar.gz
tar xvzf tkn_0.30.0_Linux_x86_64.tar.gz -C /usr/local/bin/ tkn

Building Your First Tekton Pipeline​

Let's create a simple CI pipeline for a Node.js application:

1. Create a Task for cloning a Git repository​

yaml
apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: git-clone
spec:
  workspaces:
    - name: output
  params:
    - name: url
      type: string
      description: Git repository URL
  steps:
    - name: clone
      image: alpine/git
      script: |
        git clone $(params.url) $(workspaces.output.path)/source

Save this as git-clone-task.yaml and apply:

bash
kubectl apply -f git-clone-task.yaml

2. Create a Task for testing the Node.js application​

yaml
apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: npm-test
spec:
  workspaces:
    - name: source
  steps:
    - name: install-and-test
      image: node:16
      workingDir: $(workspaces.source.path)/source
      script: |
        npm install
        npm test

Save this as npm-test-task.yaml and apply:

bash
kubectl apply -f npm-test-task.yaml

3. Create a Pipeline combining these Tasks​

yaml
apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: nodejs-test-pipeline
spec:
  workspaces:
    - name: shared-workspace
  params:
    - name: repo-url
      type: string
  tasks:
    - name: fetch-source
      taskRef:
        name: git-clone
      workspaces:
        - name: output
          workspace: shared-workspace
      params:
        - name: url
          value: $(params.repo-url)
    - name: run-tests
      taskRef:
        name: npm-test
      runAfter:
        - fetch-source
      workspaces:
        - name: source
          workspace: shared-workspace

Save this as nodejs-pipeline.yaml and apply:

bash
kubectl apply -f nodejs-pipeline.yaml

4. Create a PersistentVolumeClaim for the workspace​

yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pipeline-workspace
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

Save this as workspace-pvc.yaml and apply:

bash
kubectl apply -f workspace-pvc.yaml

5. Run the Pipeline​

yaml
apiVersion: tekton.dev/v1beta1
kind: PipelineRun
metadata:
  name: nodejs-test-run
spec:
  pipelineRef:
    name: nodejs-test-pipeline
  workspaces:
    - name: shared-workspace
      persistentVolumeClaim:
        claimName: pipeline-workspace
  params:
    - name: repo-url
      value: https://github.com/example/nodejs-sample-app

Save this as pipeline-run.yaml and apply:

bash
kubectl apply -f pipeline-run.yaml

6. Monitor the Pipeline execution​

bash
kubectl get pipelineruns
kubectl describe pipelinerun nodejs-test-run

Or, if you installed the Tekton CLI:

bash
tkn pipelinerun describe nodejs-test-run
tkn pipelinerun logs nodejs-test-run -f

Advanced Tekton Features​

Triggers​

Tekton Triggers allow you to automate pipeline execution in response to events like webhook calls from GitHub, GitLab, or other systems.

Here's a simple example of creating a Trigger for GitHub webhooks:

yaml
apiVersion: triggers.tekton.dev/v1beta1
kind: TriggerTemplate
metadata:
  name: github-template
spec:
  params:
    - name: gitrepositoryurl
    - name: gitrevision
  resourcetemplates:
    - apiVersion: tekton.dev/v1beta1
      kind: PipelineRun
      metadata:
        generateName: nodejs-test-run-
      spec:
        pipelineRef:
          name: nodejs-test-pipeline
        workspaces:
          - name: shared-workspace
            persistentVolumeClaim:
              claimName: pipeline-workspace
        params:
          - name: repo-url
            value: $(tt.params.gitrepositoryurl)
---
apiVersion: triggers.tekton.dev/v1beta1
kind: TriggerBinding
metadata:
  name: github-binding
spec:
  params:
    - name: gitrepositoryurl
      value: $(body.repository.url)
    - name: gitrevision
      value: $(body.head_commit.id)
---
apiVersion: triggers.tekton.dev/v1beta1
kind: EventListener
metadata:
  name: github-listener
spec:
  triggers:
    - bindings:
        - ref: github-binding
      template:
        ref: github-template

Conditions​

Tekton Conditions allow you to specify criteria that must be met before a Task is executed:

yaml
apiVersion: tekton.dev/v1alpha1
kind: Condition
metadata:
  name: file-exists
spec:
  params:
    - name: file-path
      type: string
  check:
    image: alpine
    script: |
      if [ -f $(params.file-path) ]; then
        exit 0
      else
        exit 1
      fi

Then in your Pipeline:

yaml
tasks:
  - name: conditional-task
    conditions:
      - conditionRef: file-exists
        params:
          - name: file-path
            value: "$(workspaces.source.path)/package.json"
    taskRef:
      name: npm-test
    # ...

When Expressions​

When expressions provide a more powerful way to conditionally execute tasks:

yaml
tasks:
  - name: build-on-main
    when:
      - input: "$(params.git-branch)"
        operator: in
        values: ["main", "master"]
    taskRef:
      name: build-app
    # ...

Custom Tasks​

Custom Tasks allow you to extend Tekton's functionality by implementing your own Task controllers:

yaml
apiVersion: tekton.dev/v1beta1
kind: CustomTask
metadata:
  name: slack-notification
spec:
  params:
    - name: message
      value: "Pipeline completed successfully!"

Real-World Application: Complete CI/CD Pipeline​

Let's build a more complete example of a CI/CD pipeline for a containerized application:

Here's how this would look in Tekton:

yaml
apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: complete-cicd-pipeline
spec:
  workspaces:
    - name: shared-workspace
    - name: docker-credentials
  params:
    - name: repo-url
      type: string
    - name: image-name
      type: string
    - name: image-tag
      type: string
      default: latest
  tasks:
    - name: fetch-source
      taskRef:
        name: git-clone
      workspaces:
        - name: output
          workspace: shared-workspace
      params:
        - name: url
          value: $(params.repo-url)
        
    - name: run-tests
      taskRef:
        name: npm-test
      runAfter:
        - fetch-source
      workspaces:
        - name: source
          workspace: shared-workspace
          
    - name: build-image
      taskRef:
        name: kaniko-build
      runAfter:
        - run-tests
      workspaces:
        - name: source
          workspace: shared-workspace
        - name: docker-config
          workspace: docker-credentials
      params:
        - name: IMAGE
          value: $(params.image-name):$(params.image-tag)
        - name: DOCKERFILE
          value: ./Dockerfile
          
    - name: deploy-to-cluster
      taskRef:
        name: kubectl-deploy
      runAfter:
        - build-image
      workspaces:
        - name: manifests
          workspace: shared-workspace
      params:
        - name: image
          value: $(params.image-name):$(params.image-tag)
        - name: manifest_dir
          value: k8s/
          
    - name: notify
      taskRef:
        name: slack-notification
      runAfter:
        - deploy-to-cluster
      params:
        - name: message
          value: "Deployment of $(params.image-name):$(params.image-tag) completed successfully!"

Best Practices for Tekton Pipelines​

  1. Reuse Tasks: Create general-purpose, reusable Tasks and share them across your organization.

  2. Use Workspaces Effectively: Use workspaces to share data between Tasks rather than passing large amounts of data as parameters.

  3. Parameterize Everything: Make your Pipelines and Tasks flexible by parameterizing values.

  4. Organize with Labels: Use consistent labeling for all your Tekton resources to help with organization and querying.

  5. Implement Timeouts: Set appropriate timeouts for your Tasks and Pipelines to prevent stuck runs.

  6. Handle Failures Gracefully: Implement proper error handling and notifications for pipeline failures.

  7. Secure Your Pipelines: Use Kubernetes secrets for sensitive information and implement proper RBAC.

  8. Monitor Pipeline Performance: Set up monitoring and alerting for your Tekton pipelines.

Debugging Tekton Pipelines​

When your pipelines don't work as expected, here are some debugging strategies:

  1. Check the status of your PipelineRun:

    bash
    kubectl describe pipelinerun <pipelinerun-name>

  2. Examine the logs of a specific TaskRun:

    bash
    kubectl logs -l tekton.dev/taskRun=<taskrun-name> -c step-<step-name>

  3. Use the Tekton CLI for more detailed information:

    bash
    tkn pipelinerun logs <pipelinerun-name> -f

  4. Check events in the namespace:

    bash
    kubectl get events

Integrating Tekton with Other Tools​

Tekton works well with various other tools in the Kubernetes ecosystem:

  • Argo CD: Use Tekton for CI and Argo CD for GitOps-based CD
  • Prometheus/Grafana: Monitor your Tekton pipelines
  • Vault: Securely manage secrets for your pipelines
  • Knative: Deploy serverless applications from your Tekton pipelines
  • Kustomize/Helm: Package and customize your Kubernetes manifests

Summary​

Tekton provides a powerful, Kubernetes-native way to build CI/CD pipelines. Its key advantages include:

  • Kubernetes-native: Runs entirely on Kubernetes, leveraging its features
  • Declarative: Pipelines and tasks are defined as Kubernetes custom resources
  • Modular: Build reusable components that can be shared across teams
  • Scalable: Automatically scales with your Kubernetes cluster
  • Extensible: Create custom tasks and extend functionality
  • Vendor-neutral: Works with any cloud provider or on-premises Kubernetes cluster

By mastering Tekton, you'll be able to create sophisticated CI/CD pipelines that integrate seamlessly with your Kubernetes environment.

Additional Resources​

Exercises​

  1. Create a simple Tekton pipeline that clones a GitHub repository and counts the lines of code.
  2. Extend the pipeline to run unit tests and report results.
  3. Build a complete CI/CD pipeline for a sample application that builds a container image and deploys it to your Kubernetes cluster.
  4. Implement a webhook-triggered pipeline using Tekton Triggers.
  5. Create a custom Task that sends pipeline results to your preferred messaging platform.

If you spot any mistakes on this website, please let me know at feedback@compilenrun.com. I’d greatly appreciate your feedback! :)