Development Guide

Guide for developing and contributing to Lynq.

First time here?

Start with the Quick Start guide to get familiar with the system before diving into development tooling.

Setup

Prerequisites

Tool	Version / Notes
Go	1.22+
kubectl	Matches target cluster
kind or minikube	Local cluster for testing
Docker	Required for image builds
make	Used for build/test helpers

Clone Repository

bash

git clone https://github.com/k8s-lynq/lynq.git
cd lynq

Install Dependencies

bash

go mod download

Local Development

Running Locally

bash

# Install CRDs
make install

# Run controller locally (uses ~/.kube/config)
make run

# Run with debug logging
LOG_LEVEL=debug make run

Local Run Limitations

make run runs the operator outside the cluster, which means:

⚠️ Webhooks are NOT available (no TLS certificates)
⚠️ No validation at admission time (invalid configs will only fail at reconciliation)
⚠️ No defaulting (all fields must be specified explicitly)

For complete testing with webhooks, deploy to cluster with cert-manager:

bash

# See Local Development with Minikube guide
./scripts/deploy-to-minikube.sh  # Includes cert-manager and webhooks

When to use make run:

Quick iteration on controller logic
Testing reconciliation loops
Debugging without webhook complications

When to deploy to cluster:

Testing webhooks (validation/defaulting)
Final testing before committing
Verifying production-like behavior

Testing Against Local Cluster

bash

# Create kind cluster
kind create cluster --name lynq-dev

# Install CRDs
make install

# Run operator
make run

Building

Build Binary

bash

# Build for current platform
make build

# Binary output: bin/manager
./bin/manager --help

Build Container Image

bash

# Build image
make docker-build IMG=myregistry/lynq:dev

# Push image
make docker-push IMG=myregistry/lynq:dev

# Build multi-platform
docker buildx build --platform linux/amd64,linux/arm64 \
  -t myregistry/lynq:dev \
  --push .

Testing

Unit Tests

bash

# Run all unit tests
make test

# Run with coverage
make test-coverage

# View coverage report
go tool cover -html=cover.out

Integration Tests

bash

# Run integration tests (requires cluster)
make test-integration

Cluster required

Integration and E2E suites create and mutate Kubernetes resources. Run them against disposable clusters.

E2E Tests

bash

# Create test cluster
kind create cluster --name e2e-test

# Run E2E tests
make test-e2e

# Cleanup
kind delete cluster --name e2e-test

Code Quality

Linting

bash

# Run linter
make lint

# Auto-fix issues
golangci-lint run --fix

Formatting

bash

# Format code
go fmt ./...

# Or use goimports
goimports -w .

Generate Code

bash

# Generate CRD manifests, RBAC, etc.
make generate

# Generate DeepCopy methods
make manifests

Project Structure

lynq/
├── api/v1/                    # CRD types
│   ├── lynqnode_types.go
│   ├── lynqhub_types.go
│   ├── lynqform_types.go
│   └── common_types.go
├── internal/controller/       # Controllers
│   ├── lynqnode_controller.go
│   ├── lynqhub_controller.go
│   └── lynqform_controller.go
├── internal/apply/            # SSA apply engine
├── internal/database/         # Database connectors
├── internal/graph/            # Dependency graph
├── internal/readiness/        # Readiness checks
├── internal/template/         # Template engine
├── internal/metrics/          # Prometheus metrics
├── config/                    # Kustomize configs
│   ├── crd/                   # CRD manifests
│   ├── rbac/                  # RBAC configs
│   ├── manager/               # Deployment configs
│   └── samples/               # Example CRs
├── test/                      # Tests
│   ├── e2e/                   # E2E tests
│   └── utils/                 # Test utilities
├── docs/                      # Documentation
└── cmd/                       # Entry point

Adding Features

New CRD Field

Update API types:

// api/v1/lynqnode_types.go
type LynqNodeSpec struct {
    NewField string `json:"newField,omitempty"`
}

Generate code:

bash

make generate
make manifests

Update controller logic
Add tests
Update documentation

New Controller

Create controller file:

// internal/controller/myresource_controller.go
package controller

type MyResourceReconciler struct {
    client.Client
    Scheme *runtime.Scheme
}

func (r *MyResourceReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
    // Implementation
}

// cmd/main.go
if err = (&controller.MyResourceReconciler{
    Client: mgr.GetClient(),
    Scheme: mgr.GetScheme(),
}).SetupWithManager(mgr); err != nil {
    // Handle error
}

Add tests

Adding a New Datasource

Lynq uses a pluggable adapter pattern for datasources, making it easy to add support for new databases or data sources.

Architecture

Quick Reference

1. Implement Interface (internal/datasource/your_adapter.go):

package datasource

type YourAdapter struct {
    conn *YourConnection
}

// QueryNodes retrieves node data
func (a *YourAdapter) QueryNodes(ctx context.Context, config QueryConfig) ([]NodeRow, error) {
    // 1. Build query using config.Table, config.ValueMappings, config.ExtraMappings
    // 2. Execute query
    // 3. Map results to []NodeRow
    // 4. Filter active nodes
    return nodes, nil
}

// Close cleans up resources
func (a *YourAdapter) Close() error {
    return a.conn.Close()
}

2. Register in Factory (internal/datasource/interface.go):

const SourceTypeYours SourceType = "yourdatasource"

func NewDatasource(sourceType SourceType, config Config) (Datasource, error) {
    switch sourceType {
    case SourceTypeYours:
        return NewYourAdapter(config)
    // ... other cases
    }
}

3. Add API Types (api/v1/lynqhub_types.go):

const SourceTypeYours SourceType = "yourdatasource"

type LynqHubSourceSpec struct {
    // +kubebuilder:validation:Enum=mysql;postgresql;yourdatasource
    Type SourceType `json:"type"`

    YourDatasource *YourDatasourceSpec `json:"yourdatasource,omitempty"`
}

4. Test:

bash

make test
make lint
make build

Full Guide

📚 Detailed Step-by-Step Guide: Contributing a New Datasource

The full guide includes:

Interface explanation with examples
Complete MySQL reference implementation walkthrough
PostgreSQL adapter example
Testing strategies
Documentation templates
PR checklist

Key Files

File	Purpose
`internal/datasource/interface.go`	Interface definition + factory
`internal/datasource/mysql.go`	Reference implementation
`internal/datasource/your_adapter.go`	Your implementation
`api/v1/lynqhub_types.go`	API types
`internal/controller/lynqhub_controller.go`	Controller integration

Example: Study MySQL Adapter

The MySQL adapter (internal/datasource/mysql.go) is a complete, production-ready reference:

bash

# View the implementation
cat internal/datasource/mysql.go

# Key sections:
# - NewMySQLAdapter(): Connection setup
# - QueryNodes(): Query + mapping + filtering
# - Close(): Resource cleanup
# - Helper functions: joinColumns(), isActive()

What to learn:

Connection pooling configuration
Query building with column mappings
Result scanning and type handling
Filtering logic (active nodes only)
Error handling patterns

Development Workflow

bash

# 1. Create adapter file
touch internal/datasource/postgres.go

# 2. Implement interface
# (Copy mysql.go as template)

# 3. Register in factory
vim internal/datasource/interface.go

# 4. Add API types
vim api/v1/lynqhub_types.go

# 5. Generate manifests
make manifests

# 6. Write tests
touch internal/datasource/postgres_test.go

# 7. Test
make test

# 8. Lint
make lint

# 9. Build
make build

# 10. Test locally
make install
make run
kubectl apply -f config/samples/postgres/

Common Patterns

SQL-based datasources (MySQL, PostgreSQL):

Use database/sql package
Build SELECT queries dynamically
Use parameterized queries for safety
Handle NULL values with sql.NullString

NoSQL datasources (MongoDB, DynamoDB):

Use native client libraries
Map documents/items to NodeRow
Handle different query syntax
Consider pagination for large datasets

REST APIs:

Use net/http client
Unmarshal JSON to structs
Map to NodeRow
Handle authentication

Tips

Start with MySQL adapter - Copy it as a template
Focus on QueryNodes() - This is the core logic
Handle errors gracefully - Return clear error messages
Filter consistently - Use the same isActive() logic
Test thoroughly - Unit tests + integration tests
Document well - Help users configure your datasource

Contributing

Contribution checklist

Always include tests, update docs, and run make lint before opening a pull request.

Workflow

Fork repository
Create feature branch
Make changes
Add tests
Run linter: make lint
Run tests: make test
Commit with conventional commits
Open Pull Request

Conventional Commits

feat: add new feature
fix: fix bug
docs: update documentation
test: add tests
refactor: refactor code
chore: maintenance tasks

Pull Request Template

markdown

## Description
Brief description of changes

## Type of Change
- [ ] Bug fix
- [ ] New feature
- [ ] Breaking change
- [ ] Documentation update

## Testing
- [ ] Unit tests added/updated
- [ ] Integration tests added/updated
- [ ] Manual testing performed

## Checklist
- [ ] Code follows style guidelines
- [ ] Self-review completed
- [ ] Documentation updated
- [ ] Tests passing

Release Process

Release automation

Tags trigger the release pipeline. Confirm CI is green before pushing a new tag.

Version Bump

Update version in:
- README.md
- config/manager/kustomization.yaml
Generate changelog
Create git tag:

bash

git tag -a v1.1.0 -m "Release v1.1.0"
git push origin v1.1.0

GitHub Actions builds and publishes release

Useful Commands

bash

# Install CRDs
make install

# Uninstall CRDs
make uninstall

# Deploy operator
make deploy IMG=<image>

# Undeploy operator
make undeploy

# Run locally
make run

# Build binary
make build

# Build container
make docker-build IMG=<image>

# Run tests
make test

# Run linter
make lint

# Generate code
make generate manifests

Development Guide ​

Setup ​

Prerequisites ​

Clone Repository ​

Install Dependencies ​

Local Development ​

Running Locally ​

Testing Against Local Cluster ​

Building ​

Build Binary ​

Build Container Image ​

Testing ​

Unit Tests ​

Integration Tests ​

E2E Tests ​

Code Quality ​

Linting ​

Formatting ​

Generate Code ​

Project Structure ​

Adding Features ​

New CRD Field ​

New Controller ​

Adding a New Datasource ​

Architecture ​

Quick Reference ​

Full Guide ​

Key Files ​

Example: Study MySQL Adapter ​

Development Workflow ​

Common Patterns ​

Tips ​

Contributing ​

Workflow ​

Conventional Commits ​

Pull Request Template ​

Release Process ​

Version Bump ​

Useful Commands ​

See Also ​

Development Guide

Setup

Prerequisites

Clone Repository

Install Dependencies

Local Development

Running Locally

Testing Against Local Cluster

Building

Build Binary

Build Container Image

Testing

Unit Tests

Integration Tests

E2E Tests

Code Quality

Linting

Formatting

Generate Code

Project Structure

Adding Features

New CRD Field

New Controller

Adding a New Datasource

Architecture

Quick Reference

Full Guide

Key Files

Example: Study MySQL Adapter

Development Workflow

Common Patterns

Tips

Contributing

Workflow

Conventional Commits

Pull Request Template

Release Process

Version Bump

Useful Commands

See Also