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Tekton CI with Tekton

This folder includes all the resources that are used to setup and run CI for Tekton using Tekton. A general concept is available with diagrams to explain the general setup.

The CI system provides the following facilities:

  • Run Tekton tasks or pipelines as GitHub checks, in response to pull request events and specific comments
  • Update the status of the check on GitHub when a job is started and when it completes
  • Filter the jobs to be executed based on the content of the PR

Where are the CI services running

All the resources used for CI are deployed in the tekton-ci namespace in the dogfooding cluster.

Setting up the response to pull requests and comments

The resources in eventlistener.yaml and ingress.yaml set up the service and ingress that are configured in repository specific webhook settings on GitHub. The Event Listener uses a secret called ci-webhook:

apiVersion: v1
data:
  secret: [Base64 encoded secret specified when creating the WebHook in GitHub]
kind: Secret
metadata:
  name: ci-webhook
  namespace: tekton-ci
type: Opaque

A domain name webhook.ci.dogfooding.tekton.dev is configured automatically in Netlify through an annotation on the ingress. The ingress in annotated so that cert-manager automatically obtains a certificate from Let's Encrypt and configures HTTPs termination on the load balancer.

The webhook configuration on GitHub side is manual. Two events are required:

  • pull_request
  • issue_comment

If more events are added to the webhook, they will be filtered out by the GitHub interceptor.

The eventlistener.yaml does not defined any trigger. Triggers are instead defined as separate resources, so that each project can define its own. There is a shared trigger that defines jobs that should run on groups of repositories.

Each project has a dedicated folder with project specific resources:

  • trigger.yaml which defines the triggers for the project (pull_request, comment)
  • template.yaml which defines the CI pipelines for the project

The Tasks and Pipelines used to define the CI Job must be available in the tekton-ci namespace. There is no facility yet to avoid name conflicts, so projects should namespace job names by including the project name in the check names.

The comment trigger requires a custom interceptor add-pr-body to enrich the event with the details of the pull request where the comment was made.

The ability to filter events based on the user requires a custom interceptor add-team-members to enrich the event payload with details about members of the GitHub org and of the repo maintainer team.

Setting up the update of the status check

Tekton is deployed the dogfooding cluster with cloud events enabled. All cloud events are sent to the tekton-events event listener. CEL filters are used to select events from CI jobs TaskRuns.

When a start, failed or succeeded event is received for a CI job, the github-template.yaml is triggered, which takes care of updating the check status on GitHub side accordingly.

Conditions must trigger github updates - because of have tasks that implement conditions must be named check-*, which is used in the trigger CEL filter to skip the associated events.

The github-template adds labels to the task runs it triggers to make it easier to associate them back with the source task run:

      labels:
        prow.k8s.io/build-id: $(tt.params.buildUUID)
        ci.tekton.dev/source-taskrun-namespace: $(tt.params.taskRunNamespace)
        ci.tekton.dev/source-taskrun-name: $(tt.params.taskRunName)

CI Job Interface

The existing overlays and bindings produce a set of parameters available to CI jobs via the trigger templates. This interface is maintained consistent across CI jobs and trigger templates:

Parameter Name Description Source Notes
buildUUID Unique GitHub Event ID X-GitHub-Delivery header base binding
package GitHub org/repo repository.full_name base binding
gitRepository GitHub repo HTML URL repository.html_url base binding
gitRevision Git rev of the HEAD commit pull_request.head.sha Added by add_pr_body for comments
gitCloneDepth Number of commits + 1 extensions.git_clone_depth Added by an overlay
pullRequestNumber Pull request number pull_request.number Added by add_pr_body or overlay for comments
pullRequestURL Pull request HTML URL pull_request.html_url Added by add_pr_body for comments
pullRequestBaseRef Pull request Base Branch pull_request.base.ref Added by add_pr_body for comments
gitHubCommand GitHub comment body comment.body Only available for comments, default for PR
labels GitHub labels for PR pull_request.labels Only available for PRs, missing for comment

Define new CI Jobs

A new CI Job requires the following:

  • a unique GitHub check name, used to identify the check on GitHub side and to trigger the job on demand
  • one or more Tasks to be executed
  • a Pipeline that maps the CI Job Interface to the Tasks
  • a PipelineRun to be added to a TriggerTemplate that runs the Pipeline with the right metadata and parameters from the event

Check Names

The check name is build according to the following convention:

TRIGGER[-PROJECT]-TEST_NAME

The TRIGGER can be:

  • pull for jobs executed against a pull request
  • periodic[-BRANCH] for periodic jobs executed against a BRANCH The BRANCH part can be omitted if the branch is the main one for the repository
  • post for jobs executed after a change is merged

The PROJECT part is optional, so job that are identical across repositories shall not include it in the name.

Example of job names:

  • pull-pipeline-build-tests
  • pull-triggers-go-coverage
  • periodic-dashboard-integration-tests
  • post-catalog-publish-tasks
  • pull-kind-label

Tasks

Tasks should be from the catalog when possible. Non catalog tasks shall be stored in the tektoncd/plumbing repo under tekton/ci/jobs if they are applicable across repos, or in the tekton/ci folder of the specific repository.

NOTE Resources from the plumbing repo are deployed automatically to the dogfooding cluster. Tasks from the catalog and from other repos must be deployed and updated manually for now.

Pipeline

Common CI pipelines shall be stored in the tektoncd/plumbing repo under tekton/ci/jobs, ideally one YAML file per pipeline.

apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: [PIPELINE NAME]
spec:
  params:
    - name: pullRequestNumber
      description: The pullRequestNumber
    - name: pullRequestBaseRef
      description: The pull request base branch
    - name: gitRepository
      description: The git repository that hosts context and Dockerfile
    - name: gitCloneDepth
      description: Number of commits in the change + 1
    - name: fileFilterRegex
      description: Names regex to be matched in the list of modified files
    - name: checkName
      description: The name of the GitHub check that this pipeline is used for
    - name: gitHubCommand
      description: The command that was used to trigger testing
    # Additional parameters may be added here as required, as long as the
    # pipeline run will be in a position to supply them based on the CI interface
  workspaces:
    - name: sources
      description: Workspace where the git repo is prepared for testing
  tasks:
    - name: clone-repo
      taskRef:
        name: git-batch-merge # from the catalog
      params:
        - name: url
          value: $(params.gitRepository)
        - name: mode
          value: "merge"
        - name: revision
          value: $(params.pullRequestBaseRef)
        - name: refspec
          value: refs/heads/$(params.pullRequestBaseRef):refs/heads/$(params.pullRequestBaseRef)
        - name: batchedRefs
          value: "refs/pull/$(params.pullRequestNumber)/head"
      workspaces:
        - name: output
          workspace: sources
    - name: check-name-matches
      taskRef:
        name: check-name-matches
      params:
        - name: gitHubCommand
          value: $(params.gitHubCommand)
        - name: checkName
          value: pull-community-teps-lint
    - name: check-git-files-changed
      runAfter: ['clone-repo']
      taskRef:
        name: check-git-files-changed
      params:
        - name: gitCloneDepth
          value: $(params.gitCloneDepth)
        - name: regex
          value: $(params.fileFilterRegex)
      workspaces:
        - name: input
          workspace: sources
    - name: [CI JOB specific name]
      when: # implicit dependency on the check tasks
        - input: $(tasks.check-name-matches.results.check)
          operator: in
          values: ["passed"]
        - input: $(tasks.check-git-files-changed.results.check)
          operator: in
          values: ["passed"]
      workspaces:
        - name: input
          workspace: sources
      taskRef:
        name: [CI JOB Task Ref]
      params:
        - # Any task specific parameter

In case the CI Job is made of multiple tasks, all should run after the task that evaluate the conditions are executed.

The check-name-matches task is required for the CI job to executed on demand via the /test [regex] command. The check-git-files-changed task is optional, it is used to only execute the CI job when relevant files have been modified.

PipelineRun

PipelineRuns are added to the relevant TriggerTemplate in the tektoncd/plumbing repo under tekton/ci/<project>/template.yaml. The shared folder is used for jobs that are shared across repos. Unless PipelineRuns require a different Trigger, they should all be added to a single TriggerTemplate.

The event listener will trigger the correct template based on the event. The PipelineRun must define specific metadata for the conditions and the downstream CEL filters to work correctly.

  - apiVersion: tekton.dev/v1beta1
    kind: PipelineRun
    metadata:
      generateName: CHECK-NAME- # generateName *MUST* be used here. The name is for information only.
      labels:
        tekton.dev/kind: ci
        tekton.dev/check-name: CHECK-NAME # *MUST* be the GitHub check name
        tekton.dev/pr-number: $(tt.params.pullRequestNumber)
        prow.k8s.io/build-id: $(tt.params.buildUUID)
      annotations:
        tekton.dev/gitRevision: "$(tt.params.gitRevision)"
        tekton.dev/gitURL: "$(tt.params.gitRepository)"
    spec:
      serviceAccountName: tekton-ci-jobs
      pipelineRef:
        name: PIPELINE_NAME # The name of the CI pipeline
      workspaces:
        - name: source
          volumeClaimTemplate:
            spec:
              accessModes:
                - ReadWriteOnce
              resources:
                requests:
                  storage: 1Gi
      params:
        - name: checkName
          value: CHECK-NAME # *MUST* be the GitHub check name
        - name: pullRequestNumber
          value: $(tt.params.pullRequestNumber)
        - name: gitCloneDepth
          value: $(tt.params.gitCloneDepth)
        - name: fileFilterRegex
          value: "some/relevant/path/**" # A RegExp to match all relevant files
          # The match is executed roughly follows:
          # git diff-tree --no-commit-id --name-only -r HEAD "$(params.gitCloneDepth) - 1" | \
          #   grep -E '$(params.fileFilterRegex)
        - name: gitHubCommand
          value: $(tt.params.gitHubCommand)
        # Extra parameters required  by the pipeline shall be passed here

NOTE The naming convention for labels and annotations may change in future as the tekton.dev namespace has been reserved for Tekton itself only.

New Trigger Template

If a TriggerTemplate for a specific repository does not exists yet, it must be created under tekton/ci/templates and named REPO-template.yaml. When a new trigger template is added, corresponding Trigger resources need to be added to use the new template when events are received.

A good starting point is to look at the two triggers already defined for the plumbing repo and replicate them for the new repo.

To react to pull requests:

apiVersion: triggers.tekton.dev/v1alpha1
kind: Trigger
metadata:
  name: plumbing-pull-request
  labels:
    ci.tekton.dev/trigger-type: github.pull-request
spec:
  interceptors:
    - cel:
        filter: >-
          body.repository.name == 'plumbing'
  bindings:
    - ref: tekton-ci-github-base
    - ref: tekton-ci-webhook-pull-request
    - ref: tekton-ci-webhook-pr-labels
    - ref: tekton-ci-clone-depth
  template:
    ref: tekton-plumbing-ci-pipeline

To react to issue comments:

apiVersion: triggers.tekton.dev/v1alpha1
kind: Trigger
metadata:
  name: plumbing-issue-comment
  labels:
    ci.tekton.dev/trigger-type: github.issue-comment
spec:
  interceptors:
    - cel:
        filter: >-
          body.repository.name == 'plumbing'
  bindings:
    - ref: tekton-ci-github-base
    - ref: tekton-ci-webhook-comment
    - ref: tekton-ci-clone-depth
    - ref: tekton-ci-webhook-issue-labels
  template:
    ref: tekton-plumbing-ci-pipeline

Integration Test Jobs with KinD

Project who want to define an test job running that run on a KinD Kubernetes cluster. The kind-e2e pipeline defines a pipeline that can clones the project repo, sets up Kubernetes in a sidecar using KinD, and runs an executable script from the project repo. The behaviour of that script can be customized through environment variables stored in an .env file in the project repo.

To run the CI job as part of the project CI, a project shall:

  • create the test script and .env file. In many cases it may be possible to re-use the existing test script that is used in Prow based e2e tests jobs
  • add a PipelineRun to the project TriggerTemplate. The PipelineRun runs the kind-e2e pipeline and passes to it the name and path of the script and .env file (a full example is available in the pipeline template):
        - name: e2e-script
          value: test/e2e-kind.sh
        - name: e2e-env
          value: test/e2e-tests-kind.env