How to write a response for kubernetes admission controller - api

Question

I am trying to write a simple admission controller for pod naming (validation) but for some reason I am generating a wrong response.
Here is my code:
package main
import (
"fmt"
"encoding/json"
"io/ioutil"
"net/http"
"github.com/golang/glog"
// for Kubernetes
"k8s.io/api/admission/v1beta1"
"k8s.io/api/core/v1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"regexp"
)
type myValidServerhandler struct {
}
// this is the handler fuction from the HTTP server
func (gs *myValidServerhandler) serve(w http.ResponseWriter, r *http.Request) {
var Body []byte
if r.Body != nil {
if data , err := ioutil.ReadAll(r.Body); err == nil {
Body = data
}
}
if len(Body) == 0 {
glog.Error("Unable to retrive Body from API")
http.Error(w,"Empty Body", http.StatusBadRequest)
return
}
glog.Info("Received Request")
// this is where I make sure the request is for the validation prefix
if r.URL.Path != "/validate" {
glog.Error("Not a Validataion String")
http.Error(w,"Not a Validataion String", http.StatusBadRequest)
return
}
// in this part the function takes the AdmissionReivew and make sure in is in the right
// JSON format
arRequest := &v1beta1.AdmissionReview{}
if err := json.Unmarshal(Body, arRequest); err != nil {
glog.Error("incorrect Body")
http.Error(w, "incorrect Body", http.StatusBadRequest)
return
}
raw := arRequest.Request.Object.Raw
pod := v1.Pod{}
if err := json.Unmarshal(raw, &pod); err != nil {
glog.Error("Error Deserializing Pod")
return
}
// this is where I make sure the pod name contains the kuku string
podnamingReg := regexp.MustCompile(`kuku`)
if podnamingReg.MatchString(string(pod.Name)) {
return
} else {
glog.Error("the pod does not contain \"kuku\"")
http.Error(w, "the pod does not contain \"kuku\"", http.StatusBadRequest)
return
}
// I think the main problem is with this part of the code because the
// error from the events I getting in the Kubernetes namespace is that
// I am sending 200 without a body response
arResponse := v1beta1.AdmissionReview{
Response: &v1beta1.AdmissionResponse{
Result: &metav1.Status{},
Allowed: true,
},
}
// generating the JSON response after the validation
resp, err := json.Marshal(arResponse)
if err != nil {
glog.Error("Can't encode response:", err)
http.Error(w, fmt.Sprintf("couldn't encode response: %v", err), http.StatusInternalServerError)
}
glog.Infof("Ready to write response ...")
if _, err := w.Write(resp); err != nil {
glog.Error("Can't write response", err)
http.Error(w, fmt.Sprintf("cloud not write response: %v", err), http.StatusInternalServerError)
}
}
The code is working as expected except for a positive output (where the pod name meets the criteria)
there is another file with a main just grabbing the TLS files and starting the HTTP service.

Answer 1

so after a few digging I found what was wrong with my code
first this part
if podnamingReg.MatchString(string(pod.Name)) {
return
} else {
glog.Error("the pod does not contain \"kuku\"")
http.Error(w, "the pod does not contain \"kuku\"", http.StatusBadRequest)
return
}
by writing "return" twice I discarded the rest of the code and more so I haven't attached the request UID to the response UID and because I am using the v1 and not the v1beta1 I needed to adding the APIVersion in the response
so the rest of the code looks like :
arResponse := v1beta1.AdmissionReview{
Response: &v1beta1.AdmissionResponse{
Result: &metav1.Status{},
Allowed: false,
},
}
podnamingReg := regexp.MustCompile(`kuku`)
if podnamingReg.MatchString(string(pod.Name)) {
fmt.Printf("the pod %s is up to the name standard", pod.Name)
arResponse.Response.Allowed = true
}
arResponse.APIVersion = "admission.k8s.io/v1"
arResponse.Kind = arRequest.Kind
arResponse.Response.UID = arRequest.Request.UID
so I needed to add the 2 parts and make sure that in case the pod name is not up to standard then I need to return the right response