#Architecture

#Architecture Overview

Tekton Pipelines is a Kubernetes-based CI/CD system that provides a set of standard Custom Resource Definitions (CRDs) to define and run CI/CD workflows as a series of steps. It's designed to be cloud-native, scalable, and extensible.

#Core Components

#1. Task

A Task is the basic building block of Tekton Pipelines:

• Defines a series of steps to execute
• Runs in a Kubernetes Pod
• Can accept inputs and produce outputs
• Executes steps in sequence

Main characteristics:

• Each step runs in its own container
• Steps share workspace volumes
• Supports parameterization
• Can define resource requirements

#2. TaskRun

TaskRun is a runtime instance of a Task:

• Creates a Pod to execute the Task
• Manages the lifecycle of the Task execution
• Collects and stores execution results
• Handles resource allocation

Workflow:

1. Creates a Pod with containers for each step
2. Executes steps in sequence
3. Manages shared volumes between steps
4. Collects execution results and status

#3. Pipeline

Pipeline defines a series of Tasks to be executed:

• Orchestrates multiple Tasks
• Defines execution order and dependencies
• Manages data flow between Tasks
• Supports conditional execution

Key features:

• Task dependency management
• Parameter passing between Tasks
• Workspace sharing across Tasks
• Conditional execution using when expressions
• Parallel execution with runAfter

#4. PipelineRun

PipelineRun is a runtime instance of a Pipeline:

• Creates TaskRuns for each Task in the Pipeline
• Manages the execution flow
• Handles resource allocation
• Collects and stores execution results

Main responsibilities:

• Orchestrating TaskRun creation
• Managing execution order
• Handling parameter passing
• Tracking overall execution status

#5. Workspaces

Workspaces provide a mechanism for sharing data:

• Shared storage between Tasks
• Support for various volume types
• Flexible mounting options
• Persistent data across Task executions

Types of storage supported:

• PersistentVolumeClaims
• ConfigMaps
• Secrets
• EmptyDir volumes
• CSI (Container Storage Interface) volumes
• Projected volumes

#Workflow

1. Pipeline Definition

   • Define Tasks with steps
   • Define Pipeline with Task dependencies
   • Configure parameters and workspaces

2. Pipeline Execution

   • Create a PipelineRun resource
   • Controller creates TaskRuns based on dependencies
   • TaskRuns create Pods to execute steps
   • Results are collected and status is updated

3. Data Flow

   • Parameters pass data between Pipeline components
   • Workspaces share files between Tasks
   • Results from Tasks can be used in subsequent Tasks

4. Completion

   • All TaskRuns complete
   • PipelineRun status is updated
   • Results are stored and available for retrieval

#Deployment Architecture

#Controller Components

1. Tekton Pipeline Controller

   • Watches for Tekton CRD instances
   • Creates and manages Kubernetes resources
   • Handles lifecycle management
   • Updates status information

2. Tekton Webhook

   • Validates Tekton resources
   • Applies defaults
   • Ensures resource consistency

3. Tekton Remote Resolvers

   • Resolves Task and Pipeline definitions from remote sources
   • Supports OCI bundles
   • Supports Git-based resolution
   • Supports HTTP-based resolution

#Runtime Components

1. TaskRun Pods

   • Container for each step
   • Init containers for setup
   • Shared volumes for workspaces
   • Sidecars for special functionality

2. Resource Management

   • Pod scheduling
   • Resource requests and limits
   • Node selection and affinity
   • Priority classes

#Security Architecture

#Authentication Mechanisms

1. Service Account Integration
   • TaskRuns and PipelineRuns use ServiceAccounts
   • Supports Kubernetes RBAC
   • Secret management for credentials

#Authorization Control

1. Resource Access Control

   • Role-based access control
   • Namespace isolation
   • Resource quotas

2. Execution Security

   • Pod security contexts
   • Network policies
   • Secure workspace handling

#Extensibility Design

#1. Custom Tasks

• Extend beyond container execution
• Custom resource implementations
• Integration with external systems

#2. Remote Resolution

• Remote Task and Pipeline definitions
• Support for OCI bundles
• Git-based resolution
• HTTP-based resolution

#3. Results and Metrics

• Task and Pipeline results
• Execution metrics
• Integration with observability systems
• Custom result processors