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· 5 min read

KCL is an open-source, constraint-based record and functional language that enhances the writing of complex configurations, including those for cloud-native scenarios. With its advanced programming language technology and practices, KCL is dedicated to promoting better modularity, scalability, and stability for configurations. It enables simpler logic writing and offers ease of automation APIs and integration with homegrown systems.

This section will update the KCL language community's latest developments every two weeks, including features, website updates, and the latest community news, helping everyone better understand the KCL community!

KCL Website: https://kcl-lang.io

Overview​

Thank you to all contributors for their outstanding work over the past two weeks (08.10-08.23 2023). Here is an overview of the key content:

🔧 Language and Toolchain Updates

  • KCL Import Tool Updates - Supports exporting JSON/YAML data to KCL configuration.
  • KCL IDE Updates - Supports right-click formatting ability, formatting individual files or parts of KCL code.
  • KCL Documentation Tool Updates - Exported documents support HTML escape.
  • KCL Package Management Tool KPM Updates - kpm run command execution and error message optimization, supports running KCL packages located in local paths.
  • KCL Language Updates - Optimized system package type check error messages and unified error message codes.

📰 Official Website and Use Case Updates

Special Thanks​

The following are listed in no particular order:

  • Thanks to @jakezhu9 for the contribution of converting JSON and YAML configuration data to KCL configuration in the KCL Import Tool 🙌 https://github.com/kcl-lang/kcl-go/pull/141
  • Thanks to @xxmao123 and @starkers for their contributions to the KCL NeoVim and Idea IDE extensions 🙌 https://github.com/kcl-lang/intellij-kcl/pull/12
  • Thanks to @kolloch, @prahaladramji, and others for their valuable feedback and discussions during the use of KCL in the past two weeks 🙌

Congratulations @jakezhu9 for becoming a KCL community Maintainer 🎉

KCL Operator​

KCL Operator provides cluster integration, allowing you to use Access Webhook to generate, mutate, or validate resources based on KCL configuration when apply resources to the cluster. Webhook will capture creation, application, and editing operations, and execute KCLRun on the configuration associated with each operation, and the KCL programming language can be used to

  • Add labels or annotations based on a condition.
  • Inject a sidecar container in all KRM resources that contain a PodTemplate.
  • Validating all KRM resources using KCL Schema, such as constraints on starting containers only in a root mode.
  • Generating KRM resources using an abstract model or combining and using different KRM APIs.

With KCL Operator, you can automate resource configuration management and security validation in a Kubernetes cluster using lightweight KCL code, without the need to develop a webhook server to dynamically mutate and validate configurations at runtime.

Furthermore, leveraging KCL's modeling and abstraction capabilities, we can define functionality abstractions/compositions for different resource APIs and expose them in the form of KCL Schema. We can further generate OpenAPI Schema definitions from KCL Schema for other clients in the cluster to use, without manually maintaining complex OpenAPI Schema definitions for API abstractions/compositions. Here is an example of using KCL Operator to modify resource annotations:

0. Prerequisites​

Prepare a Kubernetes cluster like k3d the kubectl tool.

1. Install KCL Operator​

kubectl apply -f https://raw.githubusercontent.com/kcl-lang/kcl-operator/main/config/all.yaml

Use the following command to observe and wait for the pod status to be Running.

kubectl get po

2. Deploy KCL Annotation Setting Model​

kubectl apply -f- << EOF
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
  name: set-annotation
spec:
  # Set dynamic parameters required for the annotation modification model, here we can add the labels we want to modify/add
  params:
    annotations:
      managed-by: kcl-operator
  # Reference the annotation modification model on OCI
  source: oci://ghcr.io/kcl-lang/set-annotation
EOF

3. Deploy a Pod to Verify the Model Result​

Execute the following command to deploy a Pod resource:

kubectl apply -f- << EOF
apiVersion: v1
kind: Pod
metadata:
  name: nginx
  annotations:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.2
    ports:
    - containerPort: 80
EOF
kubectl get po nginx -o yaml | grep kcl-operator

We can see the following output:

    managed-by: kcl-operator

We can see that the Nginx Pod automatically added the annotation managed-by=kcl-operator.

In addition, besides referencing an existing model for the source field of the KCLRun resource, we can directly set KCL code for the source field to achieve the same effect. For example:

apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
  name: set-annotation
spec:
  params:
    annotations:
      managed-by: kcl-operator
  # Resource modification can be achieved with just one line of KCL code
  source: |
    items = [item | {metadata.annotations: option("params").annotations} for item in option("items")]

We have provided more than 30 built-in models, and you can find more code examples in the following link: https://github.com/kcl-lang/krm-kcl/tree/main/examples

IDE Extension Updates​

In the past two weeks, we have integrated the KCL language server LSP into NeoVim and Idea, enabling the completion, navigation, and hover features supported by VS Code IDE in NeoVim and IntelliJ IDEA.

  • NeoVim KCL Extension

kcl.nvim

  • IntelliJ Extension

intellij

For more information on downloading, installation, and features of the IDE plugins, please refer to:

Resources​

❤️ Thanks to all KCL users and community members for their valuable feedback and suggestions in the community.

For more resources, please refer to

· 4 min read

What is KCL​

KCL is an open-source, constraint-based record and functional language that enhances the writing of complex configurations, including those for cloud-native scenarios. With its advanced programming language technology and practices, KCL is dedicated to promoting better modularity, scalability, and stability for configurations. It enables simpler logic writing and offers ease of automation APIs and integration with homegrown systems.

What is Helmfile​

Helmfile is a declarative specification and tool for simplifying and managing Helm Charts. The Helmfile KCL Plugin provides additional functionality to the Helmfile tool, making it more convenient and efficient to use. With the Helmfile KCL Plugin, you can:

  • Edit or validate Helm Chart configurations directly on the client-side using non-intrusive hooks. This allows you to separate the data and logic parts of Kubernetes configuration management without needing to fork the upstream Chart to modify internal logic include modifying resource labels/annotations and injecting Sidecar container configurations.
  • Validate Kubernetes resources using KCL Schema, define your own abstract models, and share them for reusability.

In this blog, we will quickly guide you through getting started with the Helmfile KCL Plugin, enabling you to easily manage your Kubernetes Helm Charts.

We will explain in detail using a simple example. With the Helmfile KCL Plugin, you do not need to install any components related to KCL. You only need the latest version of the Helmfile tool (v0.156.0+) on your local machine.

Using the Helmfile KCL Plugin​

1. Tool Installation​

First, make sure you have installed the Helmfile client tool. You can follow the instructions in the documentation link below.

https://github.com/helmfile/helmfile

2. Create the Helmfile Configuration File​

Create a file named helmfile.yaml in the root directory of your project and write the configuration using Helmfile syntax. In this file, you can specify the Helm Charts to use, configuration values, and any other functionality supported by Helmfile. Additionally, you can use the features of the KCL Plugin in helmfile.yaml to load configurations and make in-place modifications and validations to the Helm Chart.

repositories:
  - name: prometheus-community
    url: https://prometheus-community.github.io/helm-charts
releases:
  - name: prom-norbac-ubuntu
    namespace: prometheus
    chart: prometheus-community/prometheus
    set:
      - name: rbac.create
        value: false
    transformers:
      # Use KCL Plugin to mutate or validate Kubernetes manifests.
      - apiVersion: krm.kcl.dev/v1alpha1
        kind: KCLRun
        metadata:
          name: "set-annotation"
          annotations:
            config.kubernetes.io/function: |
              container:
                image: docker.io/kcllang/kustomize-kcl:v0.2.0
        spec:
          source: |
            # A single line of KCL code can be used to modify workload configurations in-place.
            items = [resource | {if resource.kind == "Deployment": metadata.annotations: {"managed-by" = "helmfile-kcl"}} for resource in option("resource_list").items]

In the above configuration, we reference the Prometheus Helm Chart and use a single line of KCL code to inject the label managed-by="helmfile-kcl" to all the Deployment resources of Prometheus.

3. Run the Helmfile Tool​

Once everything is set up, you can run the Helmfile command to deploy, manage, and maintain your Helm Charts. Use the following command to apply the configuration mentioned above to the cluster.

helmfile apply

You should see the following output if everything goes well:

Adding repo prometheus-community https://prometheus-community.github.io/helm-charts
"prometheus-community" has been added to your repositories...

...

Want More?​

For the above helmfile configuration, you can encapsulate it as a reusable logic for configuration modification without constantly writing and copying/pasting KCL code. Additionally, many commonly used Kubernetes configuration editing and validation code snippets are already packaged in the KCL official Registry: https://github.com/orgs/kcl-lang/packages

registry

In addition to supporting writing KCL code in configuration files, we also support directly referencing code snippets in Registry, as shown below

apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
  name: https-only
  annotations:
    krm.kcl.dev/version: 0.0.1
    krm.kcl.dev/type: validation
    documentation: >-
      Requires Ingress resources to be HTTPS only.  Ingress resources must
      include the `kubernetes.io/ingress.allow-http` annotation, set to `false`.
      By default a valid TLS {} configuration is required, this can be made
      optional by setting the `tlsOptional` parameter to `true`.
      More info: https://kubernetes.io/docs/concepts/services-networking/ingress/#tls
spec:
  # Use the OCI source
  source: oci://ghcr.io/kcl-lang/https-only

Specific example codes can be found here

Conclusion​

This blog provided a quick getting started guide to help you master the basics of the Helmfile KCL Plugin in just 5 minutes. Now, you can start using this powerful tool to simplify and optimize your Kubernetes application deployment process!

Resources​

For more resources, please refer to