Creating a Tekton pipeline with a Dynamic Task List -
James Land - 04 Jan 2022
Happy New Year!!! :boom:
Intro
When creating a tekton pipeline one trick I have found particularly useful especially in application pipelines is the ability to create “Dynamic Task”. By this I mean allowing the users of your pipelines to specify which task they want run.
Now if this is limited to just a single task the logic is trivial, simply surround the task by an if or with and allow the user to set myTask.enabled, but what happens if we introduce a myTask2 directly after myTask? Now we need to account for the possibility to myTask existing or not which makes thinks more complicated. Fortunately there is a pretty simple fix for this just by adding a “lastTask” variable to keep track of the last task that was run.
Example:
We have a three task that we want to run in a sequential order:
- rootTask
- optionalTask1
- optionalTask2
optionalTask1 and optionalTask2 should as their name suggest be optional. Meaning we could modify our pipeline to just run rootTask and optionalTask2 with the following values.yaml file
optionalTask1:
enabled: false
optionalTask2:
enabled: true
apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
name: my-pipeline
tasks:
- name: rootTask
taskRef:
name: root-task
kind: Task
# The `lastTask` variable will represent the last task that was run
{{- $lastTask := "rootTask" }}
# You may want some additional logic incase `optionalTask` does not exist
{{- if .Values.optionalTask1.enabled }}
- name: optionalTask1
taskRef:
name: optional-task-1
runAfter:
- {{ $lastTask }}
{{- $lastTask = "optionalTask1"}}
{{- end }}
{{- if .Values.optionalTask2.enabled }}
- name: optionalTask2
taskRef:
name: optional-task-2
runAfter:
- {{ $lastTask }}
{{- $lastTask = "optionalTask2"}}
{{- end }}
# Adding any more task from here should be a copy and paste of the above logic.