Error from karmada-search: apiserver was unable to write a JSON response

[iamyeka]

Please provide an in-depth description of the question you have:

Guided by the blog: https://karmada.io/docs/tutorials/karmada-search/, i want to get pod from the true K8s.
What i did:

1. Install karmada-search with default configs by helm chart
2. Init a clientSet by default config

restConfig, err := config.ClientConfig()
if err != nil {
	return err
}
restConfig = metadata.ConfigFor(restConfig)
clientSet, err := kubernetes.NewForConfig(restConfig)
if err != nil {
	return err
}

3. Exec a command like below

pod, err := kubeClientset.CoreV1().Pods(namespace).Get(ctx, podName, metav1.GetOptions{})

4. Error log printed in kramada-search

E0214 08:14:12.024022       1 writers.go:122] "Unhandled Error" err="apiserver was unable to write a JSON response: object *unstructured.Unstructured does not implement the protobuf marshalling interface and cannot be encoded to a protobuf message"

If i specify the restConfig of the clientSet like this: restConfig.AcceptContentTypes = "application/json", the problem is gone.

The default AcceptContentTypes is like this:

// ConfigFor returns a copy of the provided config with the
// appropriate metadata client defaults set.
func ConfigFor(inConfig *rest.Config) *rest.Config {
	config := rest.CopyConfig(inConfig)
	config.AcceptContentTypes = "application/vnd.kubernetes.protobuf,application/json"
	config.ContentType = "application/vnd.kubernetes.protobuf"
	config.NegotiatedSerializer = metainternalversionscheme.Codecs.WithoutConversion()
	if config.UserAgent == "" {
		config.UserAgent = rest.DefaultKubernetesUserAgent()
	}
	return config
}

What do you think about this question?:

Environment:

• Karmada version: 1.12.3
• Kubernetes version: 1.19.3
• Others: Installed by helm chart, with all default configs

[chaosi-zju]

If i specify the restConfig of the clientSet like this: restConfig.AcceptContentTypes = "application/json", the problem is gone.

So, what is the problem that bothers you now?

Do you mean you want to get a recommended way to avoid that Unhandled Error when querying pods?

[iamyeka]

If i specify the restConfig of the clientSet like this: restConfig.AcceptContentTypes = "application/json", the problem is gone.

So, what is the problem that bothers you now?

Do you mean you want to get a recommended way to avoid that Unhandled Error when querying pods?

Can the server handle the request that sent by the client with the default header "accept: application/vnd.kubernetes.protobuf,application/json"?

We have several k8s, and we don't want to add a field into our mysql table like "accetType" to specify AcceptContentTypes of the restConfig of the clientSet.

[RainbowMango]

Do you mean the server can only respond with application/json? What you want is for sever support application/vnd.kubernetes.protobuf,application/json?

Any idea to achieve that?

[iamyeka]

Do you mean the server can only respond with application/json? What you want is for sever support application/vnd.kubernetes.protobuf,application/json?

Any idea to achieve that?

Yes. The problem is i can't use the clientSet with the default config to get info from karmada-search. I need to explicitly set acceptType to application/json to achieve the goal which is not needed for normal k8s.

[RainbowMango]

Would you like to dig into it and try to work out a solution for your case? Feel free to send a PR for it.