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Migrating from Jenkins to Tekton

Comparison of Jenkins and Tekton concepts

This section summarizes the basic terms used in Jenkins and Tekton, and compares the equivalent terms.

Jenkins terminology

Jenkins offers declarative and scripted pipelines that are extensible using shared libraries and plugins. Some basic terms in Jenkins are as follows:

  • Pipeline: Automates the entire process of building, testing, and deploying applications, using the Groovy syntax.

  • Node: A machine capable of either orchestrating or executing a scripted pipeline.

  • Stage: A conceptually distinct subset of tasks performed in a pipeline. Plugins or user interfaces often use this block to display status or progress of tasks.

  • Step: A single task that specifies the exact action to be taken, either by using a command or a script.

Tekton terminology

Tekton uses the YAML syntax for declarative pipelines and consists of tasks. Some basic terms in Tekton are as follows:

  • Pipeline: A set of tasks in a series, in parallel, or both.

  • Task: A sequence of steps as commands, binaries, or scripts.

  • PipelineRun: Execution of a pipeline with one or more tasks.

  • TaskRun: Execution of a task with one or more steps.

    You can initiate a PipelineRun or a TaskRun with a set of inputs such as parameters and workspaces, and the execution results in a set of outputs and artifacts.

  • Workspace: In Tekton, workspaces are conceptual blocks that serve the following purposes:

    • Storage of inputs, outputs, and build artifacts.

    • Common space to share data among tasks.

    • Mount points for credentials held in secrets, configurations held in config maps, and common tools shared by an organization.

    In Jenkins, there is no direct equivalent of Tekton workspaces. You can think of the control node as a workspace, as it stores the cloned code repository, build history, and artifacts. In situations where a job is assigned to a different node, the cloned code and the generated artifacts are stored in that node, but the build history is maintained by the control node.

Mapping of concepts

The building blocks of Jenkins and Tekton are not equivalent, and a comparison does not provide a technically accurate mapping. The following terms and concepts in Jenkins and Tekton correlate in general:

Table 1. Jenkins and Tekton - basic comparison
Jenkins Tekton

Pipeline

Pipeline and PipelineRun

Stage

Task

Step

A step in a task

Migrating a sample pipeline from Jenkins to Tekton

This section provides equivalent examples of pipelines in Jenkins and Tekton and helps you to migrate your build, test, and deploy pipelines from Jenkins to Tekton.

Jenkins pipeline

Consider a Jenkins pipeline written in Groovy for building, testing, and deploying:

pipeline {
   agent any
   stages {
       stage('Build') {
           steps {
               sh 'make'
           }
       }
       stage('Test'){
           steps {
               sh 'make check'
               junit 'reports/**/*.xml'
           }
       }
       stage('Deploy') {
           steps {
               sh 'make publish'
           }
       }
   }
}

Tekton pipeline

In Tekton, the equivalent example of the Jenkins pipeline comprises of three tasks, each of which can be written declaratively using the YAML syntax:

Example build task
apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: myproject-build
spec:
  workspaces:
  - name: source
  steps:
  - image: my-ci-image
    command: ["make"]
    workingDir: $(workspaces.source.path)
Example test task:
apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: myproject-test
spec:
  workspaces:
  - name: source
  steps:
  - image: my-ci-image
    command: ["make check"]
    workingDir: $(workspaces.source.path)
  - image: junit-report-image
    script: |
      #!/usr/bin/env bash
      junit-report reports/**/*.xml
    workingDir: $(workspaces.source.path)
Example deploy task:
apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: myprojectd-deploy
spec:
  workspaces:
  - name: source
  steps:
  - image: my-deploy-image
    command: ["make deploy"]
    workingDir: $(workspaces.source.path)

You can combine the three tasks sequentially to form a Tekton pipeline:

Example: Tekton pipeline for building, testing, and deployment
apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: myproject-pipeline
spec:
  workspaces:
  - name: shared-dir
  tasks:
  - name: build
    taskRef:
      name: myproject-build
    workspaces:
    - name: source
      workspace: shared-dir
  - name: test
    taskRef:
      name: myproject-test
    workspaces:
    - name: source
      workspace: shared-dir
  - name: deploy
    taskRef:
      name: myproject-deploy
    workspaces:
    - name: source
      workspace: shared-dir

Migrating from Jenkins plugins to Tekton Hub tasks

You can extend the capability of Jenkins by using plugins. To achieve similar extensibility in Tekton, use any of the available tasks from Tekton Hub.

As an example, consider the git-clone task available in the Tekton Hub, that corresponds to the git plugin for Jenkins.

Example: git-clone task from Tekton Hub
apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
 name: demo-pipeline
spec:
 params:
   - name: repo_url
   - name: revision
 workspaces:
   - name: source
 tasks:
   - name: fetch-from-git
     taskRef:
       name: git-clone
     params:
       - name: url
         value: $(params.repo_url)
       - name: revision
         value: $(params.revision)
     workspaces:
     - name: output
       workspace: source

Extending Tekton capabilities using custom tasks and scripts

In Tekton, if you do not find the right task in Tekton Hub, or need greater control over tasks, you can create custom tasks and scripts to extend Tekton’s capabilities.

Example: Custom task for running the maven test command
apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: maven-test
spec:
  workspaces:
  - name: source
  steps:
  - image: my-maven-image
    command: ["mvn test"]
    workingDir: $(workspaces.source.path)
Example: Execute a custom shell script by providing its path
...
steps:
  image: ubuntu
  script: |
      #!/usr/bin/env bash
      /workspace/my-script.sh
...
Example: Execute a custom Python script by writing it in the YAML file
...
steps:
  image: python
  script: |
      #!/usr/bin/env python3
      print(“hello from python!”)
...

Comparison of Jenkins and Tekton execution models

Jenkins and Tekton offer similar functions but are different in architecture and execution. This section outlines a brief comparison of the two execution models.

Table 2. Comparison of execution models in Jenkins and Tekton
Jenkins Tekton

Jenkins has a control node. Jenkins executes pipelines and steps centrally, or orchestrates jobs running in other nodes.

Tekton is serverless and distributed, and there is no central dependency for execution.

The containers are launched by the control node through the pipeline.

Tekton adopts a 'container-first' approach, where every step is executed as a container running in a pod (equivalent to nodes in Jenkins).

Extensibility is achieved using plugins.

Extensibility is achieved using tasks in Tekton Hub, or by creating custom tasks and scripts.

Examples of common use cases

Both Jenkins and Tekton offer capabilities for common CI/CD use cases, such as:

  • Compiling, building, and deploying images using maven

  • Extending the core capabilities by using plugins

  • Reusing shareable libraries and custom scripts

Running a maven pipeline in Jenkins and Tekton

You can use maven in both Jenkins and Tekton workflows for compiling, building, and deploying images. To map your existing Jenkins workflow to Tekton, consider the following examples:

Example: Compile and build an image and deploy it to OpenShift using maven in Jenkins
#!/usr/bin/groovy
node('maven') {
    stage 'Checkout'
    checkout scm

    stage 'Build'
    sh 'cd helloworld && mvn clean'
    sh 'cd helloworld && mvn compile'

    stage 'Run Unit Tests'
    sh 'cd helloworld && mvn test'

    stage 'Package'
    sh 'cd helloworld && mvn package'

    stage 'Archive artifact'
    sh 'mkdir -p artifacts/deployments && cp helloworld/target/*.war artifacts/deployments'
    archive 'helloworld/target/*.war'

    stage 'Create Image'
    sh 'oc login https://kubernetes.default -u admin -p admin --insecure-skip-tls-verify=true'
    sh 'oc new-project helloworldproject'
    sh 'oc project helloworldproject'
    sh 'oc process -f helloworld/jboss-eap70-binary-build.json | oc create -f -'
    sh 'oc start-build eap-helloworld-app --from-dir=artifacts/'

    stage 'Deploy'
    sh 'oc new-app helloworld/jboss-eap70-deploy.json' }
Example: Compile and build an image and deploy it to OpenShift using maven in Tekton.
apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: maven-pipeline
spec:
  workspaces:
    - name: shared-workspace
    - name: maven-settings
    - name: kubeconfig-dir
      optional: true
  params:
    - name: repo-url
    - name: revision
    - name: context-path
  tasks:
    - name: fetch-repo
      taskRef:
        name: git-clone
      workspaces:
        - name: output
          workspace: shared-workspace
      params:
        - name: url
          value: "$(params.repo-url)"
        - name: subdirectory
          value: ""
        - name: deleteExisting
          value: "true"
        - name: revision
          value: $(params.revision)
    - name: mvn-build
      taskRef:
        name: maven
      runAfter:
        - fetch-repo
      workspaces:
        - name: source
          workspace: shared-workspace
        - name: maven-settings
          workspace: maven-settings
      params:
        - name: CONTEXT_DIR
          value: "$(params.context-path)"
        - name: GOALS
          value: ["-DskipTests", "clean", "compile"]
    - name: mvn-tests
      taskRef:
        name: maven
      runAfter:
        - mvn-build
      workspaces:
        - name: source
          workspace: shared-workspace
        - name: maven-settings
          workspace: maven-settings
      params:
        - name: CONTEXT_DIR
          value: "$(params.context-path)"
        - name: GOALS
          value: ["test"]
    - name: mvn-package
      taskRef:
        name: maven
      runAfter:
        - mvn-tests
      workspaces:
        - name: source
          workspace: shared-workspace
        - name: maven-settings
          workspace: maven-settings
      params:
        - name: CONTEXT_DIR
          value: "$(params.context-path)"
        - name: GOALS
          value: ["package"]
    - name: create-image-and-deploy
      taskRef:
        name: openshift-client
      runAfter:
        - mvn-package
      workspaces:
        - name: manifest-dir
          workspace: shared-workspace
        - name: kubeconfig-dir
          workspace: kubeconfig-dir
      params:
        - name: SCRIPT
          value: |
            cd "$(params.context-path)"
            mkdir -p ./artifacts/deployments && cp ./target/*.war ./artifacts/deployments
            oc new-project helloworldproject
            oc project helloworldproject
            oc process -f jboss-eap70-binary-build.json | oc create -f -
            oc start-build eap-helloworld-app --from-dir=artifacts/
            oc new-app jboss-eap70-deploy.json

Extending the core capabilities of Jenkins and Tekton by using plugins

Jenkins has the advantage of a large ecosystem of numerous plugins developed over the years by its extensive user base. You can search and browse the plugins in the Jenkins Plugin Index.

Tekton also has many tasks developed and contributed by the community and enterprise users. A publicly available catalog of reusable Tekton tasks are available in the Tekton Hub.

In addition, Tekton incorporates many of the plugins of the Jenkins ecosystem within its core capabilities. For example, authorization is a critical function in both Jenkins and Tekton. While Jenkins ensures authorization using the Role-based Authorization Strategy plugin, Tekton uses OpenShift’s built-in Role-based Access Control system.

Sharing reusable code in Jenkins and Tekton

Jenkins shared libraries provide reusable code for parts of Jenkins pipelines. The libraries are shared between Jenkinsfiles to create highly modular pipelines without code repetition.

Although there is no direct equivalent of Jenkins shared libraries in Tekton, you can achieve similar workflows by using tasks from the Tekton Hub, in combination with custom tasks and scripts.

Additional resources