configuration

Configuration with KCL

Prerequisite

• Firstly, download and install KCL according to the instructions, and then prepare a Kubernetes environment.

Quick Start

1. Show Config

We can run the following command to show the config.

cat nginx.k

The output is

schema Nginx:
    """Schema for Nginx configuration files"""
    http: Http

schema Http:
    server: Server

schema Server:
    listen: int | str    # The attribute `listen` can be int type or a string type.
    location?: Location  # Optional, but must be non-empty when specified

schema Location:
    root: str
    index: str

nginx = Nginx {
    http.server = {
        listen = 80
        location = {
            root = "/var/www/html"
            index = "index.html"
        }
    }
}

2. Generate YAML using KCL

Run the following command

kcl nginx.k

We can get the output YAML

nginx:
  http:
    server:
      listen: 80
      location:
        root: /var/www/html
        index: index.html

3. Configuration with Dynamic Parameters

Besides, we can dynamically receive external parameters through the KCL builtin function option. For example, for the following KCL file (db.k), we can use the KCL command line -D flag to receive an external dynamic parameter.

cat db.k

env: str = option("env") or "dev"  # The attribute `env` has a default value "dev"
database: str = option("database")
hosts = {
    dev = "postgres.dev"
    stage = "postgres.stage"
    prod = "postgres.prod"
}
dbConfig = {
    host = hosts[env]
    database = database
    port = "2023"
    conn = "postgres://${host}:${port}/${database}"
}

# Use the `-D` flag to input external parameters.
kcl db.k -D database="foo"

The output is

env: dev
database: foo
hosts:
  dev: postgres.dev
  stage: postgres.stage
  prod: postgres.prod
dbConfig:
  host: postgres.dev
  database: foo
  port: "2023"
  conn: "postgres://postgres.dev:2023/foo"