actually parse service config

balancer/grpclb/grpclb.go

@@ -374,8 +374,7 @@ func (lb *lbBalancer) handleServiceConfig(sc string) {
 	lb.mu.Lock()
 	defer lb.mu.Unlock()
 
-	// TODO: FIXME: actually parse the service config.
-	newUsePickFirst := strings.Contains(sc, `{"grpclb":{"childPolicy":[{"pickfirst":{}}]}}`)
+	newUsePickFirst := childIsPickFirst(sc)
 	if lb.usePickFirst == newUsePickFirst {
 		return
 	}
@@ -384,7 +383,6 @@ func (lb *lbBalancer) handleServiceConfig(sc string) {
 	}
 	lb.refreshSubConns(lb.backendAddrs, lb.inFallback, newUsePickFirst)
 	lb.regeneratePicker(true)
-
 }
 
 func (lb *lbBalancer) UpdateResolverState(rs resolver.State) {

balancer/grpclb/grpclb_config.go

@@ -0,0 +1,87 @@
+/*
+ *
+ * Copyright 2016 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 grpclb
+
+import (
+	"encoding/json"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/balancer/roundrobin"
+)
+
+type serviceConfig struct {
+	LoadBalancingConfig *[]map[string]*grpclbServiceConfig
+}
+
+type grpclbServiceConfig struct {
+	ChildPolicy *[]map[string]json.RawMessage
+}
+
+func parseFullServiceConfig(s string) *serviceConfig {
+	var ret serviceConfig
+	err := json.Unmarshal([]byte(s), &ret)
+	if err != nil {
+		return nil
+	}
+	return &ret
+}
+
+func parseServiceConfig(s string) *grpclbServiceConfig {
+	parsedSC := parseFullServiceConfig(s)
+	if parsedSC == nil {
+		return nil
+	}
+	lbConfigs := parsedSC.LoadBalancingConfig
+	if lbConfigs == nil {
+		return nil
+	}
+	for _, lbC := range *lbConfigs {
+		if v, ok := lbC[grpclbName]; ok {
+			return v
+		}
+	}
+	return nil
+}
+
+const (
+	roundRobinName = roundrobin.Name
+	pickFirstName  = grpc.PickFirstBalancerName
+)
+
+func childIsPickFirst(s string) bool {
+	parsedSC := parseServiceConfig(s)
+	if parsedSC == nil {
+		return false
+	}
+	childConfigs := parsedSC.ChildPolicy
+	if childConfigs == nil {
+		return false
+	}
+	for _, childC := range *childConfigs {
+		// If round_robin exists before pick_first, return false
+		if _, ok := childC[roundRobinName]; ok {
+			return false
+		}
+		// If pick_first is before round_robin, return true
+		if _, ok := childC[pickFirstName]; ok {
+			return true
+		}
+	}
+	return false
+}

balancer/grpclb/grpclb_config_test.go

@@ -0,0 +1,154 @@
+/*
+ *
+ * Copyright 2016 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 grpclb
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+)
+
+func Test_parseFullServiceConfig(t *testing.T) {
+	tests := []struct {
+		name string
+		s    string
+		want *serviceConfig
+	}{
+		{
+			name: "empty",
+			s:    "",
+			want: nil,
+		},
+		{
+			name: "success1",
+			s:    `{"loadBalancingConfig":[{"grpclb":{"childPolicy":[{"pick_first":{}}]}}]}`,
+			want: &serviceConfig{
+				LoadBalancingConfig: &[]map[string]*grpclbServiceConfig{
+					{"grpclb": &grpclbServiceConfig{
+						ChildPolicy: &[]map[string]json.RawMessage{
+							{"pick_first": json.RawMessage("{}")},
+						},
+					}},
+				},
+			},
+		},
+		{
+			name: "success2",
+			s:    `{"loadBalancingConfig":[{"grpclb":{"childPolicy":[{"round_robin":{}},{"pick_first":{}}]}}]}`,
+			want: &serviceConfig{
+				LoadBalancingConfig: &[]map[string]*grpclbServiceConfig{
+					{"grpclb": &grpclbServiceConfig{
+						ChildPolicy: &[]map[string]json.RawMessage{
+							{"round_robin": json.RawMessage("{}")},
+							{"pick_first": json.RawMessage("{}")},
+						},
+					}},
+				},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := parseFullServiceConfig(tt.s); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("parseFullServiceConfig() = %+v, want %+v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_parseServiceConfig(t *testing.T) {
+	tests := []struct {
+		name string
+		s    string
+		want *grpclbServiceConfig
+	}{
+		{
+			name: "empty",
+			s:    "",
+			want: nil,
+		},
+		{
+			name: "success1",
+			s:    `{"loadBalancingConfig":[{"grpclb":{"childPolicy":[{"pick_first":{}}]}}]}`,
+			want: &grpclbServiceConfig{
+				ChildPolicy: &[]map[string]json.RawMessage{
+					{"pick_first": json.RawMessage("{}")},
+				},
+			},
+		},
+		{
+			name: "success2",
+			s:    `{"loadBalancingConfig":[{"grpclb":{"childPolicy":[{"round_robin":{}},{"pick_first":{}}]}}]}`,
+			want: &grpclbServiceConfig{
+				ChildPolicy: &[]map[string]json.RawMessage{
+					{"round_robin": json.RawMessage("{}")},
+					{"pick_first": json.RawMessage("{}")},
+				},
+			},
+		},
+		{
+			name: "no_grpclb",
+			s:    `{"loadBalancingConfig":[{"notgrpclb":{"childPolicy":[{"round_robin":{}},{"pick_first":{}}]}}]}`,
+			want: nil,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := parseServiceConfig(tt.s); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("parseFullServiceConfig() = %+v, want %+v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_childIsPickFirst(t *testing.T) {
+	tests := []struct {
+		name string
+		s    string
+		want bool
+	}{
+		{
+			name: "invalid",
+			s:    "",
+			want: false,
+		},
+		{
+			name: "pickfirst_only",
+			s:    `{"loadBalancingConfig":[{"grpclb":{"childPolicy":[{"pick_first":{}}]}}]}`,
+			want: true,
+		},
+		{
+			name: "pickfirst_before_rr",
+			s:    `{"loadBalancingConfig":[{"grpclb":{"childPolicy":[{"pick_first":{}},{"round_robin":{}}]}}]}`,
+			want: true,
+		},
+		{
+			name: "rr_before_pickfirst",
+			s:    `{"loadBalancingConfig":[{"grpclb":{"childPolicy":[{"round_robin":{}},{"pick_first":{}}]}}]}`,
+			want: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := childIsPickFirst(tt.s); got != tt.want {
+				t.Errorf("childIsPickFirst() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

balancer/grpclb/grpclb_test.go

@@ -752,7 +752,7 @@ func TestFallback(t *testing.T) {
 }
 
 func TestGRPCLBPickFirst(t *testing.T) {
-	const grpclbServiceConfigWithPickFirst = `{"loadBalancingConfig":[{"grpclb":{"childPolicy":[{"pickfirst":{}}]}}]}`
+	const grpclbServiceConfigWithPickFirst = `{"loadBalancingConfig":[{"grpclb":{"childPolicy":[{"pick_first":{}}]}}]}`
 
 	defer leakcheck.Check(t)