vendor/google.golang.org/grpc/balancer/base/base.go

   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.
  31 package base
  32
  33 import (
  34         "google.golang.org/grpc/balancer"
  35         "google.golang.org/grpc/resolver"
  36 )
  37
  38 // PickerBuilder creates balancer.Picker.
  39 type PickerBuilder interface {
  40         // Build takes a slice of ready SubConns, and returns a picker that will be
  41         // used by gRPC to pick a SubConn.
  42         Build(readySCs map[resolver.Address]balancer.SubConn) balancer.Picker
  43 }
  44
  45 // NewBalancerBuilder returns a balancer builder. The balancers
  46 // built by this builder will use the picker builder to build pickers.
  47 func NewBalancerBuilder(name string, pb PickerBuilder) balancer.Builder {
  48         return NewBalancerBuilderWithConfig(name, pb, Config{})
  49 }
  50
  51 // Config contains the config info about the base balancer builder.
  52 type Config struct {
  53         // HealthCheck indicates whether health checking should be enabled for this specific balancer.
  54         HealthCheck bool
  55 }
  56
  57 // NewBalancerBuilderWithConfig returns a base balancer builder configured by the provided config.
  58 func NewBalancerBuilderWithConfig(name string, pb PickerBuilder, config Config) balancer.Builder {
  59         return &baseBuilder{
  60                 name:          name,
  61                 pickerBuilder: pb,
  62                 config:        config,
  63         }
  64 }