Tekton Concepts

Internal

• Tekton
• Tekton Operations
• Continuous Delivery

Overview

Tekton is a cloud-native solution for building CI/CD pipelines. Tekton installs and runs as an extension on your Kubernetes cluster and uses the well-established Kubernetes resource model. Tekton workloads execute inside Kubernetes containers. It has several components: Tekton Pipelines, Tekton CLI and Tekton Catalog. Tekton is part of the CD Foundation, a Linux Foundation project. It is implemented as a set of Kubernetes Custom Resources. Once deployed, Tekton can be accessed via Tekton CLI commands or API calls.

Task

Task

ClusterTask

A task is available in a certain namespace, while a ClusterTask is available across the entire cluster. A ClusterTask behaves identically to a task. When declaring a ClusterTask in the pipeline definition, the kind sub-field of the taskRef should be explicitly set to ClusterTask. If not specified, kind defaults to Task.

apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
[...]
spec:
  tasks:
    - name: some-cluster-task
      taskRef:
        name: some-task
        kind: ClusterTask
 ...

Custom Task

• https://tekton.dev/docs/pipelines/pipelines/#using-custom-tasks
• https://github.com/tektoncd/community/blob/main/teps/0002-custom-tasks.md

Run

Instantiates a Custom Task for execution when specific inputs.

To PROCESS: https://tekton.dev/docs/pipelines/runs/

Step

Step

TaskRun

Include discussion on pod templates:

TaskRun

Pipeline

Pipeline

PipelineRun

PipelineRun

Workspaces

Workspaces

Trigger

Implemented as part of the Tekton Triggers component.

Resource

• Understand the relationship between Resources and PipelineResources.
• Understand transition from PipelineResources to Tasks, read https://tekton.dev/docs/pipelines/migrating-v1alpha1-to-v1beta1/#replacing-pipelineresources-with-tasks
• Parse https://tekton.dev/docs/pipelines/resources/ and map it on the new implementation.

Resources are used to share data between steps and tasks, and depending on which direction they are looked at, the can be input or output resources. Resources are connected to tasks and pipelines by taskRuns and pipelineRuns, respectively. A run must include the actual addresses of resources, such as the URLs of repositories, its task or pipeline needs.

Example of resources:

• git repository
• a pull request
• a container image
• a Kubernetes cluster
• storage: an object, a directory, etc.
• a CloudEvent

Input Resource

The input is defined relative to a step. Examples of input resources are: git repository.

Output Resource

The output is defined relative to a step. Examples of output resources: container image.

PipelineResource

Deprecated. Defines locations for inputs ingested and outputs produced by the steps in tasks. Also see Task Resources.

TO PROCESS:

• The from field: https://tekton.dev/docs/pipelines/pipelines/#using-the-from-field

Result

https://tekton.dev/docs/results/

Tekton Results aims to help users logically group CI/CD workload history and separate out long term result storage away from the Pipeline controller.

TO PROCESS:

• Using Results in Pipelines: https://tekton.dev/docs/pipelines/pipelines/#using-results
• Consuming task execution results in finally: https://tekton.dev/docs/pipelines/pipelines/#consuming-task-execution-results-in-finally

Building Block

Tekton documentation refers to "building blocks". Those are ...

LimitRange

TO PROCESS:

• https://tekton.dev/docs/pipelines/taskruns/#specifying-limitrange-values
• https://kubernetes.io/docs/concepts/policy/limit-range/
• https://tekton.dev/docs/pipelines/limitrange/

Events

Events

Bundles

Bundles

Conditions

https://tekton.dev/docs/pipelines/conditions/

Conditions are deprecated, use when expressions instead.

Parameters

Parameters

Security

Security

Metrics

TO PROCESS: https://tekton.dev/docs/pipelines/metrics/

Tekton Runtime Model

Tekton Pipelines tracks the state of a pipeline using Kubernetes annotations, which are projected inside each step container in the form of files with the Kubernetes Downward API. The step container entrypoint binary watches these projected files and will only start the command the step is supposed to execute only if a specific annotation appears as file.

In addition, Tekton Pipelines schedules some containers to run automatically before and after the step containers to support built-in features such as the retrieval of input resources and the uploading the outputs to wherever they are supposed to go.

TO PROCESS: Labels and Annotations: https://tekton.dev/docs/pipelines/labels/

Tekton Components

Tekton Pipelines

https://github.com/tektoncd/pipeline/blob/main/docs/README.md

Tekton Pipelines is the component that implements the core functionality of Tekton and sets the foundation for other components. It is implemented as a set of Kubernetes Custom Resources.

Tekton Pipeline Operations

• Installation

Tekton CLI

https://github.com/tektoncd/cli/blob/main/README.md

Tekton CLI provides the command interface called tkn.

Tekton CLI Operations

• Installation

Tekton API

Tekton APIs are currently available for Pipelines and Triggers allow you to programmatically interact with the Tekton components.

Tekton Catalog

https://github.com/tektoncd/catalog/blob/v1beta1/README.md

Tekton Catalog is a repository of community-contributed Tekton building blocks.

Tekton Hub

https://hub.tekton.dev

https://github.com/tektoncd/hub/blob/main/README.md

Tekton Hub is a web GUI to access Tekton Catalog.

Tekton Triggers

https://github.com/tektoncd/triggers/blob/main/README.md

Tekton Triggers provide triggers, which allow instantiating pipelines based on events (a PR merge, etc.)

Tekton Dashboard

https://github.com/tektoncd/dashboard/blob/main/README.md

Tekton Dashboard is the web GUI that displays information about pipeline execution.

Tekton Operator

https://github.com/tektoncd/operator/blob/main/README.md

Tekton Operator is the implementation of the Kubernetes Operator pattern that assists with the operation of the Tekton projects.

Programming Model

Process Task Authoring Recommendations: https://github.com/tektoncd/catalog/blob/main/recommendations.md

Variables

TO PROCESS:

• https://tekton.dev/docs/pipelines/variables/
• https://tekton.dev/docs/pipelines/tasks/#using-variable-substitution
• Variables available in a Task https://tekton.dev/docs/pipelines/variables/#variables-available-in-a-task
• Variables available in a Pipeline https://tekton.dev/docs/pipelines/variables/#variables-available-in-a-pipeline
• Fields that accept variable substitutions: https://tekton.dev/docs/pipelines/variables/#fields-that-accept-variable-substitutions
• Using variable substitution in pipelines: https://tekton.dev/docs/pipelines/pipelines/#using-variable-substitution

Code Examples

TO PROCESS:

• Code Examples: https://tekton.dev/docs/pipelines/tasks/#code-examples
• Code Examples: https://github.com/tektoncd/pipeline/tree/main/examples
• TaskRun code examples: https://tekton.dev/docs/pipelines/taskruns/#code-examples
• https://github.com/tektoncd/pipeline/blob/release-v0.35.x/examples/v1beta1/taskruns/run-steps-as-non-root.yaml
• Pipeline code examples: https://github.com/tektoncd/pipeline/tree/main/examples
• Variable substitution: https://tekton.dev/docs/pipelines/tasks/#using-variable-substitution

Start the list here:

• How to do this
• How to do that

Playground

https://github.com/ovidiuf/playground/tree/master/tekton