Tekton trigger flow from github

Question

I am learning Tekton (for business), coming from github actions (private).

The Tekton docs (or any other tutorial I could find) have instructions on how to automatically start a pipeline from a github push. Basically they all somewhat follow the below flow: (I am aware of PipelineRun/TaskRun etc)

Eventlistener - Trigger - TriggerTemplate - Pipeline

All above steps are basically configuration steps you need to take (and files to create and maintain), one easier than the other but as far as I can see they also need to be taken for every single repo you're maintaining. Compared to github actions where I just need 1 file in my repo describing everything I need this seems very elaborate (if not cumbersome).

Am I missing something ? Or is this just the way to go ? Thanks !

Answer 1

they also need to be taken for every single repo you're maintaining

You're mistaken here.

The EventListener receives the payload of your webhook.

Based on your TriggerBinding, you may map fields from that GitHub payload, to variables, such as your input repository name/URL, a branch or ref to work with, ...

For GitHub push events, one way to do it would be with a TriggerBinding such as the following:

apiVersion: triggers.tekton.dev/v1alpha1
kind: TriggerBinding
metadata:
  name: github-push
spec:
  params:
  - name: gitbranch
    value: $(extensions.branch_name) # uses CEL interceptor, see EL below
  - name: gitrevision
    value: $(body.after) # uses body from webhook payload
  - name: gitrepositoryname
    value: $(body.repository.name)
  - name: gitrepositoryurl
    value: $(body.repository.clone_url)

We may re-use those params within our TriggerTemplate, passing them to our Pipelines / Tasks:

apiVersion: triggers.tekton.dev/v1alpha1
kind: TriggerTemplate
metadata:
  name: github-pipelinerun
spec:
  params:
  - name: gitbranch
  - name: gitrevision
  - name: gitrepositoryname
  - name: gitrepositoryurl
  resourcetemplates:
  - apiVersion: tekton.dev/v1beta1
    kind: PipelineRun
    metadata:
      generateName: github-job-
    spec:
      params:
      - name: identifier
        value: "demo-$(tt.params.gitrevision)"
      pipelineRef:
        name: ci-docker-build
      resources:
      - name: app-git
        resourceSpec:
          type: git
          params:
          - name: revision
            value: $(tt.params.gitrevision)
          - name: url
            value: $(tt.params.gitrepositoryurl)
      - name: ci-image
        resourceSpec:
          type: image
          params:
          - name: url
            value: registry.registry.svc.cluster.local:5000/ci/$(tt.params.gitrepositoryname):$(tt.params.gitrevision)
      - name: target-image
        resourceSpec:
          type: image
          params:
          - name: url
            value: registry.registry.svc.cluster.local:5000/ci/$(tt.params.gitrepositoryname):$(tt.params.gitbranch)
      timeout: 2h0m0s

Using the following EventListener:

apiVersion: triggers.tekton.dev/v1alpha1
kind: EventListener
metadata:
  name: github-listener
spec:
  triggers:
  - name: github-push-listener
    interceptors:
    - name: GitHub push payload check
      github:
        secretRef:
          secretName: github-secret # a Secret you would create (option)
          secretKey: secretToken    # the secretToken in my Secret matches to secret configured in GitHub, for my webhook
        eventTypes:
        - push
    - name: CEL extracts branch name
      ref:
        name: cel
      params:
      - name: overlays
        value:
        - key: truncated_sha
          expression: "body.after.truncate(7)"
        - key: branch_name
          expression: "body.ref.split('/')[2]"
    bindings:
    - ref: github-push
    template:
      ref: github-pipelinerun

And now, you can expose that EventListener, with an Ingress, to receive notifications from any of your GitHub repository.