TriggerTemplates

A TriggerTemplate is a resource that specifies a blueprint for the resource, such as a TaskRun or PipelineRun, that you want to instantiate and/or execute when your EventListener detects an event. It exposes parameters that you can use anywhere within your resource’s template.

TriggerTemplates currently support the following Tekton Pipelines resources:

Structure of a TriggerTemplate

Below is an example TriggerTemplate definition:

apiVersion: triggers.tekton.dev/v1beta1
kind: TriggerTemplate
metadata:
  name: pipeline-template
spec:
  params:
  - name: gitrevision
    description: The git revision
    default: main
  - name: gitrepositoryurl
    description: The git repository url
  - name: message
    description: The message to print
    default: This is the default message
  - name: contenttype
    description: The Content-Type of the event
    default: text/plain
  resourcetemplates:
  - apiVersion: tekton.dev/v1beta1
    kind: PipelineRun
    metadata:
      generateName: simple-pipeline-run-
    spec:
      pipelineRef:
        name: simple-pipeline
      params:
      - name: message
        value: $(tt.params.message)
      - name: contenttype
        value: $(tt.params.contenttype)
      - name: git-revision
        value: $(tt.params.gitrevision)
      - name: git-url
        value: $(tt.params.gitrepositoryurl)
      workspaces:
      - name: git-source
        emptyDir: {}

Keep the following in mind:

• If you don’t specify the namespace, Tekton resolves it to the namespace of the EventListener that specifies the given TriggerTemplate.

• The $(uid) variable is implicitly available to the resource templates you specify in your TriggerTemplate with a random value, just like the postfix generated by the Kubernetes generateName metadata field. This can be useful for resource templates that use internal references.

• Tekton adds the following labels to all resource templates within a TriggerTemplate:

  • tekton.dev/eventlistenter:<EventListenerName> to help with housekeeping and garbage collection.
  • tekton.dev/triggers-eventid:<EventID> to track resources created by a specific event.

• To support arbitrary resource types, Tekton resolves resource templates internally as byte blobs. Because of this, Tekton only validates these resources when processing an event rather than at the creation of the TriggerTemplate. The default assigned cluster role to the EventListener service account only allows creating Tekton resources. You will need to add the appropriate roles to the EventListener’s service account to be able to create other non Tekton resources.

• As of Tekton Pipelines 0.8.0, you can embed resource definitions directly in your TriggerTemplate definition. To prevent a race condition between creating and using resources, you must embed each resource definition within the PipelineRun or TaskRun that uses that resource.

Specifying parameters

A TriggerTemplate allows you to declare parameters supplied by the associated TriggerBinding and/or EventListener as follows:

• Declare your parameters in the params section of the TriggerTemplate definition.

• You must specify a name and can optionally specify a description and a default value.

• Tekton applies the value of the default field for each entry in the params array of your TriggerTemplate if it can’t find a corresponding value in the associated TriggerBinding or cannot successfully extract the value from an HTTP header or body payload.

• You can reference tt.params in the resourcetemplates section of your TriggerTemplate to make your TriggerTemplate reusable.

• When you specify parameters in your resource template definitions, Tekton replaces the specified string with the parameter name, for example $(tt.params.name). Therefore, simple string and number value replacements work fine directly in your YAML file. However, if a string has a numerical prefix, such as 123abcd, Tekton can misinterpret it to be a number and throw an error. In such cases, enclose the affected parameter key in quotes (").

Embedding JSON objects within resource templates

Tekton no longer replaces quotes (") with escaped quotes (\") and does not perform any escaping on variables in your resource templates. If you are embedding JSON objects as variables in your templates, you must not enclose them with quotes ("). If you have existing TriggerTemplates that use escaped quotes, add an annotation to work around this behavior change.

For example, consider the following JSON object:

{
  "title": "this is \"demo\" body",
  "object": {
    "name": "testing"
  }
}

If your TriggerBinding extracts $(body.title) then Tekton inserts it into your TriggerTemplate as this is a \"demo\" body. To work around this, annotate the TriggerTemplate as follows:

apiVersion: triggers.tekton.dev/v1alpha1
kind: TriggerTemplate
metadata:
  name: escaped-tt
  annotations:
    triggers.tekton.dev/old-escape-quotes: "true"
spec:
  params:
  - name: title
    description: The title from the incoming body

This way, Tekton passes the value as this is a \""demo\"" body, which in itself is not valid JSON code; however, if you use a value with $(body.object) in a resource template that specifically passes it as a quoted string, then this workaround restores normal operation. This can also be useful for parsing a string containing JSON code in a command.