snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

internal/xds/xdsclient/xdslbregistry/xdslbregistry.go

@@ -0,0 +1,82 @@
+/*
+ *
+ * Copyright 2023 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package xdslbregistry provides a registry of converters that convert proto
+// from load balancing configuration, defined by the xDS API spec, to JSON load
+// balancing configuration.
+package xdslbregistry
+
+import (
+	"encoding/json"
+	"fmt"
+
+	v3clusterpb "github.com/envoyproxy/go-control-plane/envoy/config/cluster/v3"
+)
+
+var (
+	// m is a map from proto type to Converter.
+	m = make(map[string]Converter)
+)
+
+// Register registers the converter to the map keyed on a proto type. Must be
+// called at init time. Not thread safe.
+func Register(protoType string, c Converter) {
+	m[protoType] = c
+}
+
+// SetRegistry sets the xDS LB registry. Must be called at init time. Not thread
+// safe.
+func SetRegistry(registry map[string]Converter) {
+	m = registry
+}
+
+// Converter converts raw proto bytes into the internal Go JSON representation
+// of the proto passed. Returns the json message,  and an error. If both
+// returned are nil, it represents continuing to the next proto.
+type Converter func([]byte, int) (json.RawMessage, error)
+
+// ConvertToServiceConfig converts a proto Load Balancing Policy configuration
+// into a json string. Returns an error if:
+//   - no supported policy found
+//   - there is more than 16 layers of recursion in the configuration
+//   - a failure occurs when converting the policy
+func ConvertToServiceConfig(lbPolicy *v3clusterpb.LoadBalancingPolicy, depth int) (json.RawMessage, error) {
+	// "Configurations that require more than 16 levels of recursion are
+	// considered invalid and should result in a NACK response." - A51
+	if depth > 15 {
+		return nil, fmt.Errorf("lb policy %v exceeds max depth supported: 16 layers", lbPolicy)
+	}
+
+	// "This function iterate over the list of policy messages in
+	// LoadBalancingPolicy, attempting to convert each one to gRPC form,
+	// stopping at the first supported policy." - A52
+	for _, policy := range lbPolicy.GetPolicies() {
+		converter := m[policy.GetTypedExtensionConfig().GetTypedConfig().GetTypeUrl()]
+		// "Any entry not in the above list is unsupported and will be skipped."
+		// - A52
+		if converter == nil {
+			continue
+		}
+		json, err := converter(policy.GetTypedExtensionConfig().GetTypedConfig().GetValue(), depth)
+		if json == nil && err == nil {
+			continue
+		}
+		return json, err
+	}
+	return nil, fmt.Errorf("no supported policy found in policy list +%v", lbPolicy)
+}