Source: grpclb_config.go in package google.golang.org/grpc/balancer/grpclb

* * Copyright 2019 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"
	"google.golang.org/grpc/serviceconfig"
)

const (
	roundRobinName = roundrobin.Name
	pickFirstName  = grpc.PickFirstBalancerName
)

type grpclbServiceConfig struct {
	serviceconfig.LoadBalancingConfig
	ChildPolicy *[]map[string]json.RawMessage
}

func (b *lbBuilder) ParseConfig(lbConfig json.RawMessage) (serviceconfig.LoadBalancingConfig, error) {
	ret := &grpclbServiceConfig{}
	if err := json.Unmarshal(lbConfig, ret); err != nil {
		return nil, err
	}
	return ret, nil
}

func childIsPickFirst(sc *grpclbServiceConfig) bool {
	if sc == nil {
		return false
	}
	childConfigs := sc.ChildPolicy
	if childConfigs == nil {
		return false
	}

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