1/* 2 * 3 * Copyright 2017 gRPC authors. 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 * 17 */ 18 19// Package base defines a balancer base that can be used to build balancers with 20// different picking algorithms. 21// 22// The base balancer creates a new SubConn for each resolved address. The 23// provided picker will only be notified about READY SubConns. 24// 25// This package is the base of round_robin balancer, its purpose is to be used 26// to build round_robin like balancers with complex picking algorithms. 27// Balancers with more complicated logic should try to implement a balancer 28// builder from scratch. 29// 30// All APIs in this package are experimental. 31package base 32 33import ( 34 "google.golang.org/grpc/balancer" 35 "google.golang.org/grpc/resolver" 36) 37 38// PickerBuilder creates balancer.Picker. 39type PickerBuilder interface { 40 // Build returns a picker that will be used by gRPC to pick a SubConn. 41 Build(info PickerBuildInfo) balancer.Picker 42} 43 44// PickerBuildInfo contains information needed by the picker builder to 45// construct a picker. 46type PickerBuildInfo struct { 47 // ReadySCs is a map from all ready SubConns to the Addresses used to 48 // create them. 49 ReadySCs map[balancer.SubConn]SubConnInfo 50} 51 52// SubConnInfo contains information about a SubConn created by the base 53// balancer. 54type SubConnInfo struct { 55 Address resolver.Address // the address used to create this SubConn 56} 57 58// Config contains the config info about the base balancer builder. 59type Config struct { 60 // HealthCheck indicates whether health checking should be enabled for this specific balancer. 61 HealthCheck bool 62} 63 64// NewBalancerBuilder returns a base balancer builder configured by the provided config. 65func NewBalancerBuilder(name string, pb PickerBuilder, config Config) balancer.Builder { 66 return &baseBuilder{ 67 name: name, 68 pickerBuilder: pb, 69 config: config, 70 } 71} 72