feat: relations (#303)

* feat: relations

On-behalf-of: @SAP a.shcherbatiuk@sap.com
Signed-off-by: Artem Shcherbatiuk <vertex451@gmail.com>

Author: vertex451

gateway/resolver/relations.go

@@ -0,0 +1,203 @@
+package resolver
+
+import (
+	"context"
+	"strings"
+
+	"github.com/graphql-go/graphql"
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+)
+
+// referenceInfo holds extracted reference details
+type referenceInfo struct {
+	name      string
+	namespace string
+	kind      string
+	apiGroup  string
+}
+
+// RelationResolver creates a GraphQL resolver for relation fields
+// Relationships are only enabled for GetItem queries to prevent N+1 problems in ListItems and Subscriptions
+func (r *Service) RelationResolver(fieldName string, gvk schema.GroupVersionKind) graphql.FieldResolveFn {
+	return func(p graphql.ResolveParams) (interface{}, error) {
+		// Determine operation type from GraphQL path analysis
+		operation := r.detectOperationFromGraphQLInfo(p)
+
+		r.log.Debug().
+			Str("fieldName", fieldName).
+			Str("operation", operation).
+			Str("graphqlField", p.Info.FieldName).
+			Msg("RelationResolver called")
+
+		// Check if relationships are allowed in this query context
+		if !r.isRelationResolutionAllowedForOperation(operation) {
+			r.log.Debug().
+				Str("fieldName", fieldName).
+				Str("operation", operation).
+				Msg("Relationship resolution disabled for this operation type")
+			return nil, nil
+		}
+
+		parentObj, ok := p.Source.(map[string]any)
+		if !ok {
+			return nil, nil
+		}
+
+		refInfo := r.extractReferenceInfo(parentObj, fieldName)
+		if refInfo.name == "" {
+			return nil, nil
+		}
+
+		return r.resolveReference(p.Context, refInfo, gvk)
+	}
+}
+
+// extractReferenceInfo extracts reference details from a *Ref object
+func (r *Service) extractReferenceInfo(parentObj map[string]any, fieldName string) referenceInfo {
+	name, _ := parentObj["name"].(string)
+	if name == "" {
+		return referenceInfo{}
+	}
+
+	namespace, _ := parentObj["namespace"].(string)
+	apiGroup, _ := parentObj["apiGroup"].(string)
+
+	kind, _ := parentObj["kind"].(string)
+	if kind == "" {
+		// Fallback: infer kind from field name (e.g., "role" -> "Role")
+		kind = cases.Title(language.English).String(fieldName)
+	}
+
+	return referenceInfo{
+		name:      name,
+		namespace: namespace,
+		kind:      kind,
+		apiGroup:  apiGroup,
+	}
+}
+
+// resolveReference fetches a referenced Kubernetes resource using strict conflict resolution
+func (r *Service) resolveReference(ctx context.Context, ref referenceInfo, targetGVK schema.GroupVersionKind) (interface{}, error) {
+	// Use provided reference info to override GVK if specified
+	finalGVK := targetGVK
+	if ref.apiGroup != "" {
+		finalGVK.Group = ref.apiGroup
+	}
+	if ref.kind != "" {
+		finalGVK.Kind = ref.kind
+	}
+
+	// Convert sanitized group to original before calling the client
+	finalGVK.Group = r.getOriginalGroupName(finalGVK.Group)
+
+	obj := &unstructured.Unstructured{}
+	obj.SetGroupVersionKind(finalGVK)
+
+	key := client.ObjectKey{Name: ref.name}
+	if ref.namespace != "" {
+		key.Namespace = ref.namespace
+	}
+
+	if err := r.runtimeClient.Get(ctx, key, obj); err != nil {
+		// For "not found" errors, return nil to allow graceful degradation
+		// This handles cases where referenced resources are deleted or don't exist
+		if apierrors.IsNotFound(err) {
+			return nil, nil
+		}
+
+		// For other errors (network, permission, etc.), log and return the actual error
+		// This ensures proper error propagation for debugging and monitoring
+		r.log.Error().
+			Err(err).
+			Str("operation", "resolve_relation").
+			Str("group", finalGVK.Group).
+			Str("version", finalGVK.Version).
+			Str("kind", finalGVK.Kind).
+			Str("name", ref.name).
+			Str("namespace", ref.namespace).
+			Msg("Unable to resolve referenced object")
+		return nil, err
+	}
+
+	// Happy path: resource found successfully
+	return obj.Object, nil
+}
+
+// isRelationResolutionAllowedForOperation checks if relationship resolution should be enabled for the given operation type
+func (r *Service) isRelationResolutionAllowedForOperation(operation string) bool {
+	// Only allow relationships for GetItem and GetItemAsYAML operations
+	switch operation {
+	case GET_ITEM, GET_ITEM_AS_YAML:
+		return true
+	case LIST_ITEMS, SUBSCRIBE_ITEM, SUBSCRIBE_ITEMS:
+		return false
+	default:
+		// For unknown operations, be conservative and disable relationships
+		r.log.Debug().Str("operation", operation).Msg("Unknown operation type, disabling relationships")
+		return false
+	}
+}
+
+// detectOperationFromGraphQLInfo analyzes GraphQL field path to determine operation type
+// This looks at the parent field context to determine if we're in a list, single item, or subscription
+func (r *Service) detectOperationFromGraphQLInfo(p graphql.ResolveParams) string {
+	if p.Info.Path == nil {
+		return "unknown"
+	}
+
+	// Walk up the path to find the parent resolver context
+	path := p.Info.Path
+	for path.Prev != nil {
+		path = path.Prev
+
+		// Check if we find a parent field that indicates the operation type
+		if fieldName, ok := path.Key.(string); ok {
+			fieldLower := strings.ToLower(fieldName)
+
+			// Check for subscription patterns
+			if strings.Contains(fieldLower, "subscription") {
+				r.log.Debug().
+					Str("parentField", fieldName).
+					Msg("Detected subscription context from parent field")
+				return SUBSCRIBE_ITEMS
+			}
+
+			// Check for mutation patterns
+			if strings.HasPrefix(fieldLower, "create") {
+				return CREATE_ITEM
+			}
+			if strings.HasPrefix(fieldLower, "update") {
+				return UPDATE_ITEM
+			}
+			if strings.HasPrefix(fieldLower, "delete") {
+				return DELETE_ITEM
+			}
+
+			// Check for YAML patterns
+			if strings.HasSuffix(fieldLower, "yaml") {
+				return GET_ITEM_AS_YAML
+			}
+
+			// Check for list patterns (plural without args, or explicitly plural fields)
+			if strings.HasSuffix(fieldName, "s") && !strings.HasSuffix(fieldName, "Status") {
+				// This looks like a plural field, likely a list operation
+				r.log.Debug().
+					Str("parentField", fieldName).
+					Msg("Detected list context from parent field")
+				return LIST_ITEMS
+			}
+		}
+	}
+
+	// If we can't determine from parent context, assume it's a single item operation
+	// This is the safe default that allows relationships for queries
+	r.log.Debug().
+		Str("currentField", p.Info.FieldName).
+		Msg("Could not determine operation type from GraphQL path, defaulting to GetItem (enables relations)")
+	return GET_ITEM
+}

gateway/resolver/resolver.go

@@ -25,11 +25,23 @@ import (
 	"github.com/openmfp/golang-commons/logger"
 )
 
+const (
+	LIST_ITEMS       = "ListItems"
+	GET_ITEM         = "GetItem"
+	GET_ITEM_AS_YAML = "GetItemAsYAML"
+	CREATE_ITEM      = "CreateItem"
+	UPDATE_ITEM      = "UpdateItem"
+	DELETE_ITEM      = "DeleteItem"
+	SUBSCRIBE_ITEM   = "SubscribeItem"
+	SUBSCRIBE_ITEMS  = "SubscribeItems"
+)
+
 type Provider interface {
 	CrudProvider
 	CustomQueriesProvider
 	CommonResolver() graphql.FieldResolveFn
 	SanitizeGroupName(string) string
+	RelationResolver(fieldName string, gvk schema.GroupVersionKind) graphql.FieldResolveFn
 }
 
 type CrudProvider interface {
@@ -65,7 +77,7 @@ func New(log *logger.Logger, runtimeClient client.WithWatch) *Service {
 // ListItems returns a GraphQL CommonResolver function that lists Kubernetes resources of the given GroupVersionKind.
 func (r *Service) ListItems(gvk schema.GroupVersionKind, scope v1.ResourceScope) graphql.FieldResolveFn {
 	return func(p graphql.ResolveParams) (interface{}, error) {
-		ctx, span := otel.Tracer("").Start(p.Context, "ListItems", trace.WithAttributes(attribute.String("kind", gvk.Kind)))
+		ctx, span := otel.Tracer("").Start(p.Context, LIST_ITEMS, trace.WithAttributes(attribute.String("kind", gvk.Kind)))
 		defer span.End()
 
 		gvk.Group = r.getOriginalGroupName(gvk.Group)
@@ -87,6 +99,7 @@ func (r *Service) ListItems(gvk schema.GroupVersionKind, scope v1.ResourceScope)
 		list.SetGroupVersionKind(gvk)
 
 		var opts []client.ListOption
+
 		// Handle label selector argument
 		if labelSelector, ok := p.Args[LabelSelectorArg].(string); ok && labelSelector != "" {
 			selector, err := labels.Parse(labelSelector)
@@ -117,16 +130,16 @@ func (r *Service) ListItems(gvk schema.GroupVersionKind, scope v1.ResourceScope)
 			return nil, err
 		}
 
-		err = validateSortBy(list.Items, sortBy)
-		if err != nil {
-			log.Error().Err(err).Str(SortByArg, sortBy).Msg("Invalid sortBy field path")
-			return nil, err
+		if sortBy != "" {
+			if err := validateSortBy(list.Items, sortBy); err != nil {
+				log.Error().Err(err).Str(SortByArg, sortBy).Msg("Invalid sortBy field path")
+				return nil, err
+			}
+			sort.Slice(list.Items, func(i, j int) bool {
+				return compareUnstructured(list.Items[i], list.Items[j], sortBy) < 0
+			})
 		}
 
-		sort.Slice(list.Items, func(i, j int) bool {
-			return compareUnstructured(list.Items[i], list.Items[j], sortBy) < 0
-		})
-
 		items := make([]map[string]any, len(list.Items))
 		for i, item := range list.Items {
 			items[i] = item.Object