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Version: 0.7

Introduction

This guide shows you how to use the KCL language and CLIs to complete the deployment of an application running in Kubernetes. We call the abstraction of application operation and maintenance configuration as Server, and its instance as Application. It is essentially an operation and maintenance model defined by KCL.

In actual production, the application online generally needs to update several k8s resources:

  • Namespace
  • Deployment
  • Service

This guide requires you to have a basic understanding of Kubernetes. If you are not familiar with the relevant concepts, please refer to the links below:

Prerequisites

Before we start, we need to complete the following steps:

  1. Install kcl

  2. Clone the Konfig repo

git clone https://github.com/kcl-lang/konfig.git && cd konfig

Quick Start

1. Compiling

The programming language of the project is KCL, not JSON/YAML which Kubernetes recognizes, so it needs to be compiled to get the final output.

Enter stack dir examples/appops/nginx-example/dev and compile:

cd examples/appops/nginx-example/dev && kcl run

The output YAML is:

apiVersion: apps/v1
kind: Deployment
metadata:
name: sampleappprod
namespace: sampleapp
spec:
replicas: 1
selector:
matchLabels:
app.kubernetes.io/name: sampleapp
app.kubernetes.io/env: prod
app.kubernetes.io/instance: sampleapp-prod
app.k8s.io/component: sampleappprod
template:
metadata:
labels:
app.kubernetes.io/name: sampleapp
app.kubernetes.io/env: prod
app.kubernetes.io/instance: sampleapp-prod
app.k8s.io/component: sampleappprod
spec:
containers:
- image: nginx:1.7.8
name: main
ports:
- containerPort: 80
protocol: TCP
resources:
limits:
cpu: 100m
memory: 100Mi
ephemeral-storage: 1Gi
requests:
cpu: 100m
memory: 100Mi
ephemeral-storage: 1Gi
---
apiVersion: v1
kind: Namespace
metadata:
name: sampleapp
---
apiVersion: v1
kind: Service
metadata:
name: nginx
namespace: sampleapp
spec:
ports:
- nodePort: 30201
port: 80
targetPort: 80
selector:
app.kubernetes.io/name: sampleapp
app.kubernetes.io/env: prod
app.kubernetes.io/instance: sampleapp-prod
app.k8s.io/component: sampleappprod
type: NodePort

After compiling, we can see three resources:

  • A Deployment with the name nginx-exampledev
  • A Namespace with the name nginx-example
  • A Service with the name nginx-example

2. Modification

The image attribute in the Server model is used to declare the application's container image. We can modify the image value in base/main.k to modify or upgrade the image:

14c14
< image = "nginx:1.7.8"
---
> image = "nginx:latest"

Recompile the configuration code to obtain the modified YAML output:

kcl run
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-exampledev
namespace: nginx-example
spec:
replicas: 1
selector:
matchLabels:
app.kubernetes.io/name: nginx-example
app.kubernetes.io/env: dev
app.kubernetes.io/instance: nginx-example-dev
app.kubernetes.io/component: nginx-exampledev
template:
metadata:
labels:
app.kubernetes.io/name: nginx-example
app.kubernetes.io/env: dev
app.kubernetes.io/instance: nginx-example-dev
app.kubernetes.io/component: nginx-exampledev
spec:
containers:
- image: nginx:latest
name: main
ports:
- containerPort: 80
protocol: TCP
resources:
limits:
cpu: 100m
memory: 100Mi
ephemeral-storage: 1Gi
requests:
cpu: 100m
memory: 100Mi
ephemeral-storage: 1Gi
---
apiVersion: v1
kind: Namespace
metadata:
name: nginx-example
---
apiVersion: v1
kind: Service
metadata:
name: nginx-example
namespace: nginx-example
spec:
ports:
- nodePort: 30201
port: 80
targetPort: 80
selector:
app.kubernetes.io/name: nginx-example
app.kubernetes.io/env: dev
app.kubernetes.io/instance: nginx-example-dev
app.kubernetes.io/component: nginx-exampledev
type: NodePort

Summary

This document mainly introduces how to use the KCL and Konfig library to deploy a Long Running application running in Kubernetes.