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Version: 0.10

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 -D env=dev

The output YAML is:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: sampleappdev
  namespace: sampleapp
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: sampleapp
      app.kubernetes.io/env: dev
      app.kubernetes.io/instance: sampleapp-dev
      app.k8s.io/component: sampleappdev
  template:
    metadata:
      labels:
        app.kubernetes.io/name: sampleapp
        app.kubernetes.io/env: dev
        app.kubernetes.io/instance: sampleapp-dev
        app.k8s.io/component: sampleappdev
    spec:
      containers:
        - env:
            - name: MY_ENV
              value: MY_VALUE
          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"
          volumeMounts: []
---
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: dev
    app.kubernetes.io/instance: sampleapp-dev
    app.k8s.io/component: sampleappdev
  type: NodePort

After compiling, we can see three resources:

  • A Deployment with the name sampleappprod
  • A Namespace with the name sampleapp
  • A Service with the name nginx

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: sampleappdev
  namespace: sampleapp
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: sampleapp
      app.kubernetes.io/env: dev
      app.kubernetes.io/instance: sampleapp-dev
      app.k8s.io/component: sampleappdev
  template:
    metadata:
      labels:
        app.kubernetes.io/name: sampleapp
        app.kubernetes.io/env: dev
        app.kubernetes.io/instance: sampleapp-dev
        app.k8s.io/component: sampleappdev
    spec:
      containers:
        - env:
            - name: MY_ENV
              value: MY_VALUE
          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"
          volumeMounts: []
---
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: dev
    app.kubernetes.io/instance: sampleapp-dev
    app.k8s.io/component: sampleappdev

Resources​

  • More examples can be found here
  • Konfig schema reference document can be found here

Summary​

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