A Declarative Continuous Delivery Toolkit For Kubernetes

Table of Contents

• Introduction
• Installation
• Getting Started
• Contributions
• License

Introduction

Traditional GitOps tools often rely on YAML for configuration, which can lead to verbosity and complexity. Declcd leverages CUE, a configuration language with a more concise and expressive syntax, making it easier to define and maintain your desired cluster state.

Installation

Note

Currently we don't maintain our binaries in any package manager.

Linux(x86_64):

curl -L -o declcd.tar.gz https://github.com/kharf/declcd/releases/download/v0.22.9/declcd_linux_x86_64.tar.gz
tar -xf declcd.tar.gz
chmod +x declcd
./declcd -h

MacOS(x86_64):

curl -L -o declcd.tar.gz https://github.com/kharf/declcd/releases/download/v0.22.9/declcd_darwin_x86_64.tar.gz
tar -xf declcd.tar.gz
chmod +x declcd
./declcd -h

MacOS(arm64):

curl -L -o declcd.tar.gz https://github.com/kharf/declcd/releases/download/v0.22.9/declcd_darwin_arm64.tar.gz
tar -xf declcd.tar.gz
chmod +x declcd
./declcd -h

Getting Started

Important

It is strongly recommended to familiarize yourself with CUE before you begin, as it is one of the cornerstones of Declcd.

Basics of Declcd

While Declcd does not enforce any kind of repository structure, there is one constraint for the declaration of the cluster state. Every top-level CUE value in a package, which is not hidden and not a Definition, has to be what Declcd calls a Component. Declcd Components effectively describe the desired cluster state and currently exist in two forms: Manifests and HelmReleases. A Manifest is a typical Kubernetes Object, which you would normally describe in yaml format. A HelmRelease is an instance of a Helm Chart. All Components share the attribute to specify Dependencies to other Components. This helps Declcd to identify the correct order in which to apply all objects onto a Kubernetes cluster. See schema.

Important

Dependency relationships are represented in the form of a Directed Acyclic Graph, thus cyclic dependencies lead to errors.

From Start to Finish

Note

For the purpose of demonstration this guide uses Kind to create a Kubernetes cluster and Github. We recommend that beginners follow along with both.

Important

Requirements:

• Declcd
• Git
• Go
• An empty git repository
• A GitHub personal access token with repo permissions

Create Kind Cluster

kind create cluster --name declcd

Initialize a Declcd GitOps Repository

mkdir mygitops
cd mygitops
git init
git remote add origin git@github.com:user/mygitops.git
# init Declcd gitops repository as a CUE module
export CUE_EXPERIMENT=modules
export CUE_REGISTRY=ghcr.io/kharf
declcd init github.com/user/mygitops@v0
go mod init mygitops
declcd verify
git add .
git commit -m "Init declcd"
git push -u origin main

See CUE module reference for valid CUE module paths.

Install Declcd onto your Kubernetes Cluster

declcd install \
  -u git@github.com:user/mygitops.git \
  -b main \
  --name dev \
  -t <token>
git add .
git commit -m "Install declcd"

Deploy a Manifest and a HelmRelease

Get Go Kubernetes Structs and import them as CUE schemas.

Tip

Use CUE modules and provide these CUE schemas as OCI container.

go get k8s.io/api/core/v1
cue get go k8s.io/api/core/v1
cue get go k8s.io/apimachinery/pkg/api/resource
cue get go k8s.io/apimachinery/pkg/apis/meta/v1
cue get go k8s.io/apimachinery/pkg/runtime
cue get go k8s.io/apimachinery/pkg/types
cue get go k8s.io/apimachinery/pkg/watch
cue get go k8s.io/apimachinery/pkg/util/intstr
mkdir infrastructure
touch infrastructure/prometheus.cue

Edit infrastructure/prometheus.cue and add:

package infrastructure

import (
	"github.com/kharf/declcd/schema/component"
	corev1 "k8s.io/api/core/v1"
)

// Public Declcd Manifest Component
ns: component.#Manifest & {
	content: corev1.#Namespace & {
		apiVersion: "v1"
		kind:       "Namespace"
		metadata: {
			name: "monitoring"
		}
	}
}

// Public Declcd HelmRelease Component
prometheusStack: component.#HelmRelease & {
	dependencies: [
    // Declcd automatically generates ids for Components, which are used for dependency constraints.
		ns.id,
	]
	name:      "prometheus-stack"
  // Use namespace name Component reference to reduce redundancy
	namespace: ns.content.metadata.name
	chart: {
		name:    "kube-prometheus-stack"
		repoURL: "https://prometheus-community.github.io/helm-charts"
		version: "58.2.1"
	}
	values: {
		prometheus: prometheusSpec: serviceMonitorSelectorNilUsesHelmValues: false
	}
}

See getting-started example.

declcd verify
git add .
git commit -m "feat: install kube-prometheus-stack"

Contributions

We welcome contributions! To contribute to Declcd, follow these steps:

1. Fork the repository.
2. Create a new branch for your feature or bug fix.
3. Make your changes.
4. Create tests and run them in a containerized environment via Dagger with:

   cd build/
   # Run all tests
   go run cmd/test/main.go
   
   # Or run a specific test
   go run cmd/test/main.go MyTest pkg/mypackage

5. Create a PR.
6. Ensure that your code passes the CI/CD checks. For more information, see CONTRIBUTING.md.

License

Copyright 2023.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.