mutation

Mutation 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 transformer.k

items = lambda {
    # Construct resource and params
    resource = option("resource_list")
    items = resource.items
    params = resource.functionConfig.spec.params
    new_replicas: int = params.replicas
    min_replicas: int = params.min_replicas or 0
    max_replicas: int = params.max_replicas or 99999
    # Define the validation function
    validate_replica_limit = lambda item, min_replicas: int, max_replicas: int, new_replicas: int {
        replicas = item.spec.replicas or 0
        assert min_replicas < replicas < max_replicas, "The provided number of replicas ${replicas} is not allowed for ${item.kind}: ${item.metadata.name}. Allowed range: ${min} - ${max}"
        item | {
            if typeof(new_replicas) == "int":
                spec.replicas = new_replicas
        }
    }
    # Validate All resource
    [validate_replica_limit(i, min_replicas, max_replicas, new_replicas) for i in items]
}()

The meaning of this function is to set the replicates of the deployment resource to our expected value params.replicas, which is defined in the file kcl.yaml.

cat kcl.yaml

The output is

kcl_cli_configs:
  files:
    - ./transformer.k
  path_selector:
    - items
kcl_options:
  # Follow KRM KCL Spec
  - key: resource_list
    value:
      # Input KRM list
      items:
        - apiVersion: apps/v1
          kind: Deployment
          metadata:
            name: nginx-deployment
            labels:
              app: nginx
          spec:
            replicas: 3  # Will be mutated with the field `functionConfig.spec.params.replicas`
            selector:
              matchLabels:
                app: nginx
            template:
              metadata:
                labels:
                  app: nginx
              spec:
                containers:
                - name: nginx
                  image: nginx:1.14.2
                  ports:
                  - containerPort: 80
      functionConfig:
        spec:
          params:
            min_replicas: 0
            max_replicas: 5
            replicas: 4

We can execute the following command to obtain the results after mutation.

kcl

The output is

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: nginx
  name: nginx-deployment
spec:
  replicas: 4
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx:1.14.2
        name: nginx
        ports:
        - containerPort: 80

More Documents

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