i would like to parse kubernetes manifest file (json/yaml) and be able to convert them to k8s structures (to later on manipulate them)
I know there is the NewYAMLOrJSONDecoder().Decode() function (https://github.com/kubernetes/apimachinery/blob/master/pkg/util/yaml/decoder.go) to read a json/yaml file, but the next step is: how to convert them to k8s structure/type?
i.e. if I read a yaml file with a Namespace object, how to convert it to a core/v1/namespace interface for example
Regards,
Thanks svenwltr, I was not aware we can do like this.
In the same time, I manage to find not a better approach but a different one:
package main
import (
"flag"
"fmt"
"os"
"io"
"path/filepath"
"log"
"encoding/json"
//"time"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/clientcmd"
"k8s.io/client-go/discovery"
"k8s.io/client-go/dynamic"
"k8s.io/apimachinery/pkg/util/yaml"
"k8s.io/apimachinery/pkg/runtime"
"k8s.io/apimachinery/pkg/runtime/schema"
"k8s.io/apimachinery/pkg/api/meta"
"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
)
func main() {
var kubeconfig *string
if home := homeDir(); home != "" {
kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
} else {
kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
}
flag.Parse()
// use the current context in kubeconfig
config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
if err != nil {
panic(err.Error())
}
// create the clientset
clientset, err := kubernetes.NewForConfig(config)
if err != nil {
panic(err.Error())
}
f,err := os.Open("namespace.yaml")
if err!=nil {
log.Fatal(err)
}
d := yaml.NewYAMLOrJSONDecoder(f,4096)
dd := clientset.Discovery()
apigroups,err := discovery.GetAPIGroupResources(dd)
if err != nil {
log.Fatal(err)
}
restmapper := discovery.NewRESTMapper(apigroups,meta.InterfacesForUnstructured)
for {
// https://github.com/kubernetes/apimachinery/blob/master/pkg/runtime/types.go
ext := runtime.RawExtension{}
if err := d.Decode(&ext); err!=nil {
if err == io.EOF {
break
}
log.Fatal(err)
}
fmt.Println("raw: ",string(ext.Raw))
versions := &runtime.VersionedObjects{}
//_, gvk, err := objectdecoder.Decode(ext.Raw,nil,versions)
obj, gvk, err := unstructured.UnstructuredJSONScheme.Decode(ext.Raw,nil,versions)
fmt.Println("obj: ",obj)
// https://github.com/kubernetes/apimachinery/blob/master/pkg/api/meta/interfaces.go
mapping, err := restmapper.RESTMapping(gvk.GroupKind(), gvk.Version)
if err != nil {
log.Fatal(err)
}
restconfig := config
restconfig.GroupVersion = &schema.GroupVersion {
Group: mapping.GroupVersionKind.Group,
Version: mapping.GroupVersionKind.Version,
}
dclient,err := dynamic.NewClient(restconfig)
if err != nil {
log.Fatal(err)
}
// https://github.com/kubernetes/client-go/blob/master/discovery/discovery_client.go
apiresourcelist, err := dd.ServerResources()
if err != nil {
log.Fatal(err)
}
var myapiresource metav1.APIResource
for _,apiresourcegroup := range(apiresourcelist) {
if apiresourcegroup.GroupVersion == mapping.GroupVersionKind.Version {
for _,apiresource := range(apiresourcegroup.APIResources) {
//fmt.Println(apiresource)
if apiresource.Name == mapping.Resource && apiresource.Kind == mapping.GroupVersionKind.Kind {
myapiresource = apiresource
}
}
}
}
fmt.Println(myapiresource)
// https://github.com/kubernetes/client-go/blob/master/dynamic/client.go
var unstruct unstructured.Unstructured
unstruct.Object = make(map[string]interface{})
var blob interface{}
if err := json.Unmarshal(ext.Raw,&blob); err != nil {
log.Fatal(err)
}
unstruct.Object = blob.(map[string]interface{})
fmt.Println("unstruct:",unstruct)
ns := "default"
if md,ok := unstruct.Object["metadata"]; ok {
metadata := md.(map[string]interface{})
if internalns,ok := metadata["namespace"]; ok {
ns = internalns.(string)
}
}
res := dclient.Resource(&myapiresource,ns)
fmt.Println(res)
us,err := res.Create(&unstruct)
if err != nil {
log.Fatal(err)
}
fmt.Println("unstruct response:",us)
}
}
func homeDir() string {
if h := os.Getenv("HOME"); h != "" {
return h
}
return os.Getenv("USERPROFILE") // windows
}
import (
v1 "k8s.io/api/core/v1"
"k8s.io/apimachinery/pkg/runtime"
"k8s.io/apimachinery/pkg/runtime/serializer"
"k8s.io/client-go/kubernetes/scheme"
)
func decode(data []byte) (*v1.Namespace, error) {
decoder := serializer.NewCodecFactory(scheme.Scheme).UniversalDecoder()
object := &v1.Namespace{}
err := runtime.DecodeInto(decoder, data, object)
if err != nil {
return nil, err
}
return object, nil
}
Pass SchemeGroupVersion generated for your CRDs to UniversalDecoder call, if needed.
Use runtime.Decode instead of runtime.DecodeInto to decode unspecified object type.
This question is very similar to How to deserialize Kubernetes YAML file, but this question is a bit outdated, since the package names changed.
Also it doesn't directly use the go client, which means there might be another solution to this.
Here is a example:
package main
import (
"fmt"
"k8s.io/kubernetes/pkg/api"
_ "k8s.io/kubernetes/pkg/api/install"
_ "k8s.io/kubernetes/pkg/apis/extensions/install"
"k8s.io/kubernetes/pkg/apis/extensions/v1beta1"
)
var json = `
{
"apiVersion": "extensions/v1beta1",
"kind": "Deployment",
"metadata": null,
"name": "my-nginx",
"replicas": 2,
"spec": null,
"template": {
"metadata": {
"labels": {
"run": "my-nginx"
}
},
"spec": {
"containers": [
{
"image": "nginx",
"name": "my-nginx",
"ports": [
{
"containerPort": 80
}
]
}
]
}
}
}
`
func main() {
// decode := api.Codecs.UniversalDecoder().Decode
decode := api.Codecs.UniversalDeserializer().Decode
obj, _, err := decode([]byte(json), nil, nil)
if err != nil {
fmt.Printf("%#v", err)
}
deployment := obj.(*v1beta1.Deployment)
fmt.Printf("%#v\n", deployment)
}
Notes
.../install packages are important, since they define which types can get decodedUniversalDecoder and UniversalDeserializer is