[shell-operator] fix: patch CRD conversion without overwriting fields

pkg/webhook/conversion/crd_client_config.go

@@ -2,11 +2,12 @@ package conversion
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"time"
 
 	extv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
-	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/types"
 
 	klient "github.com/flant/kube-client/client"
 	"github.com/flant/shell-operator/pkg"
@@ -24,48 +25,51 @@ type CrdClientConfig struct {
 
 var SupportedConversionReviewVersions = []string{"v1", "v1beta1"}
 
-func (c *CrdClientConfig) Update(ctx context.Context) error {
+// PatchConversion points spec.conversion of the CRD at this operator's webhook
+// server, leaving every other field of the CRD alone.
+func (c *CrdClientConfig) PatchConversion(ctx context.Context) error {
 	var (
 		retryTimeout = 15 * time.Second
 		retryBudget  = 60 // 60 times * 15 sec = 15 min
-		client       = c.KubeClient
 	)
 
-tryToGetCRD:
-	crd, err := client.ApiExt().CustomResourceDefinitions().Get(ctx, c.CrdName, metav1.GetOptions{})
+	conv, err := json.Marshal(&extv1.CustomResourceConversion{
+		Strategy: extv1.WebhookConverter,
+		Webhook: &extv1.WebhookConversion{
+			ClientConfig: &extv1.WebhookClientConfig{
+				Service: &extv1.ServiceReference{
+					Namespace: c.Namespace,
+					Name:      c.ServiceName,
+					Path:      &c.Path,
+				},
+				CABundle: c.CABundle,
+			},
+			ConversionReviewVersions: SupportedConversionReviewVersions,
+		},
+	})
 	if err != nil {
-		if retryBudget > 0 {
-			retryBudget--
-			time.Sleep(retryTimeout)
-			goto tryToGetCRD
-		}
-
-		return fmt.Errorf("get CRD: %w", err)
+		return fmt.Errorf("marshal conversion: %w", err)
 	}
 
-	if crd.Spec.Conversion == nil {
-		crd.Spec.Conversion = new(extv1.CustomResourceConversion)
-	}
-	crd.Spec.Conversion.Strategy = extv1.WebhookConverter
+	patch := []byte(`[{"op":"add","path":"/spec/conversion","value":` + string(conv) + `}]`)
 
-	if crd.Spec.Conversion.Webhook == nil {
-		crd.Spec.Conversion.Webhook = new(extv1.WebhookConversion)
-	}
-	crd.Spec.Conversion.Webhook.ClientConfig = &extv1.WebhookClientConfig{
-		URL: nil,
-		Service: &extv1.ServiceReference{
-			Namespace: c.Namespace,
-			Name:      c.ServiceName,
-			Path:      &c.Path,
-		},
-		CABundle: c.CABundle,
-	}
-	crd.Spec.Conversion.Webhook.ConversionReviewVersions = SupportedConversionReviewVersions
+	// The CRD is often absent when a hook registers its conversion bindings, so the
+	// patch is retried on the budget the Get used to hold.
+	for {
+		_, err = c.KubeClient.ApiExt().CustomResourceDefinitions().Patch(ctx, c.CrdName, types.JSONPatchType, patch, pkg.DefaultPatchOptions())
+		if err == nil {
+			return nil
+		}
 
-	_, err = client.ApiExt().CustomResourceDefinitions().Update(ctx, crd, pkg.DefaultUpdateOptions())
-	if err != nil {
-		return fmt.Errorf("update CRD: %w", err)
-	}
+		if retryBudget == 0 {
+			return fmt.Errorf("patch CRD conversion: %w", err)
+		}
+		retryBudget--
 
-	return nil
+		select {
+		case <-ctx.Done():
+			return fmt.Errorf("patch CRD conversion: %w", ctx.Err())
+		case <-time.After(retryTimeout):
+		}
+	}
 }

pkg/webhook/conversion/manager.go

@@ -94,9 +94,9 @@ func (m *WebhookManager) Start() error {
 	}
 
 	for _, clientCfg := range m.ClientConfigs {
-		err = clientCfg.Update(ctx)
+		err = clientCfg.PatchConversion(ctx)
 		if err != nil {
-			return fmt.Errorf("update CRD: %w", err)
+			return fmt.Errorf("patch CRD conversion: %w", err)
 		}
 	}