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 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.
46 type 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.
54 type 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.
59 type 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.
65 func NewBalancerBuilder(name string, pb PickerBuilder, config Config) balancer.Builder {
66 return &baseBuilder{
67 name: name,
68 pickerBuilder: pb,
69 config: config,
70 }
71 }
72