draft: Added RLS Cluster Specifier Plugin

xds/internal/balancer/cdsbalancer/cdsbalancer.go

@@ -21,6 +21,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"strings"
 
 	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/balancer/base"
@@ -42,7 +43,8 @@ import (
 )
 
 const (
-	cdsName = "cds_experimental"
+	cdsName       = "cds_experimental"
+	clusterPrefix = "cluster:"
 )
 
 var (
@@ -179,7 +181,7 @@ func (b *cdsBalancer) handleClientConnUpdate(update *ccUpdate) {
 		b.handleErrorFromUpdate(err, true)
 		return
 	}
-	b.clusterHandler.updateRootCluster(update.clusterName)
+	b.clusterHandler.updateRootCluster(strings.TrimPrefix(update.clusterName, clusterPrefix))
 }
 
 // handleSecurityConfig processes the security configuration received from the

xds/internal/clusterspecifier/rls/rls.go

@@ -0,0 +1,96 @@
+/*
+ *
+ * Copyright 2021 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 rls implements the RLS cluster specifier plugin.
+package rls
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/golang/protobuf/proto"
+	"github.com/golang/protobuf/ptypes"
+
+	"google.golang.org/grpc/xds/internal/clusterspecifier"
+	"google.golang.org/protobuf/types/known/anypb"
+)
+
+func init() {
+	clusterspecifier.Register(rls{})
+}
+
+type rls struct{}
+
+func (rls) TypeURLs() []string {
+	return []string{"google.golang.org/grpc/xds/internal/clusterspecifier/rls/RouteLookupClusterSpecifier"}
+}
+
+// Same as balancer/rls/internal.lbConfigJSON
+type lbConfigJSON struct {
+	RouteLookupConfig                json.RawMessage
+	ChildPolicy                      []map[string]json.RawMessage
+	ChildPolicyConfigTargetFieldName string
+}
+
+func (rls) ParseClusterSpecifierConfig(cfg proto.Message) (clusterspecifier.BalancerConfig, error) {
+	if cfg == nil {
+		return nil, fmt.Errorf("rls_csp: nil configuration message provided")
+	}
+	any, ok := cfg.(*anypb.Any)
+	if !ok {
+		return nil, fmt.Errorf("rls_csp: error parsing config %v: unknown type %T", cfg, cfg)
+	}
+	rlcs := new(RouteLookupClusterSpecifier)
+
+	if err := ptypes.UnmarshalAny(any, rlcs); err != nil {
+		return nil, fmt.Errorf("rls_csp: error parsing config %v: %v", cfg, err)
+	}
+	rlcJSON, err := json.Marshal(rlcs.GetRouteLookupConfig())
+	if err != nil {
+		return nil, fmt.Errorf("rls_csp: error marshaling config: %v: %v", rlcs.GetRouteLookupConfig(), err)
+	}
+
+	lbCfgJSON := &lbConfigJSON{
+		RouteLookupConfig: rlcJSON,
+		ChildPolicy: []map[string]json.RawMessage{
+			{
+				"cds_experimental": {},
+			},
+		},
+		ChildPolicyConfigTargetFieldName: "cluster",
+	}
+
+	rawJSON, err := json.Marshal(lbCfgJSON)
+	if err != nil {
+		return nil, fmt.Errorf("rls_csp: error marshaling config %v: %v", lbCfgJSON, err)
+	}
+
+	// _, err := rls.ParseConfig(rawJSON) (will this function need to change its logic at all?)
+	// if err != nil {
+	// return nil, fmt.Errorf("error: %v", err)
+	// }
+
+	cfgRet := clusterspecifier.BalancerConfig{}
+
+	err = json.Unmarshal(rawJSON, cfgRet)
+	if err != nil {
+		return nil, fmt.Errorf("error: %v", err)
+	}
+
+	return cfgRet, nil
+}