gokuberneteskubernetes-go-client

How to deserialize Kubernetes YAML file


How can I deserialize a Kubernetes YAML file into an Go struct? I took a look into the kubectl code, but somehow I get an error for every YAML file:

no kind "Deployment" is registered for version "apps/v1beta1"

This is an MWE:

package main

import (
    "fmt"

    "k8s.io/client-go/pkg/api"
)

var service = `
apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: my-nginx
spec:
  replicas: 2
  template:
    metadata:
      labels:
        run: my-nginx
    spec:
      containers:
      - name: my-nginx
        image: nginx
        ports:
        - containerPort: 80
`

func main() {
    decode := api.Codecs.UniversalDecoder().Decode
    //decode := api.Codecs.UniversalDeserializer().Decode

    obj, _, err := decode([]byte(service), nil, nil)
    if err != nil {
        panic(err)
    }

    fmt.Printf("%#v\n", obj)
}

I am using client version 2.0.0. The glide.yaml looks like this:

package: test/stackoverflow
import:
- package: k8s.io/client-go
  version: ^2.0.0

These are the references to kubectl:

Unfortunately, the docs are very confusing to me, so I have no idea how to tackle this problem.

Edit:

This problem also exists with other resource types:


Solution

  • You need to import _ "k8s.io/client-go/pkg/apis/extensions/install" otherwise the schema is empty, see also docs.

    The complete working example is:

    $ go get -u github.com/golang/dep/cmd/dep
    $ dep init
    $ go run main.go
    

    With the following main.go:

    package main
    
    import (
        "fmt"
    
        "k8s.io/client-go/pkg/api"
        _ "k8s.io/client-go/pkg/api/install"
        _ "k8s.io/client-go/pkg/apis/extensions/install"
    )
    
    var deployment = `
    apiVersion: extensions/v1beta1
    kind: Deployment
    metadata:
    name: my-nginx
    spec:
    replicas: 2
    template:
      metadata:
        labels:
          run: my-nginx
      spec:
        containers:
        - name: my-nginx
          image: nginx
          ports:
          - containerPort: 80
    `
    
    func main() {
        // decode := api.Codecs.UniversalDecoder().Decode
        decode := api.Codecs.UniversalDeserializer().Decode
    
        obj, _, err := decode([]byte(deployment), nil, nil)
        if err != nil {
            fmt.Printf("%#v", err)
        }
    
        fmt.Printf("%#v\n", obj)
    }
    

    Note that I also imported _ "k8s.io/client-go/pkg/api/install" for you so that you can use objects in v1 such as pods or services.

    EDIT: Kudos to my colleague Stefan Schimanski who proposed the initial solution.