1 /*
2 *
3 * Copyright 2024 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 gracefulswitch
20 21 import (
22 "encoding/json"
23 "fmt"
24 25 "google.golang.org/grpc/balancer"
26 "google.golang.org/grpc/serviceconfig"
27 )
28 29 type lbConfig struct {
30 serviceconfig.LoadBalancingConfig
31 32 childBuilder balancer.Builder
33 childConfig serviceconfig.LoadBalancingConfig
34 }
35 36 // ChildName returns the name of the child balancer of the gracefulswitch
37 // Balancer.
38 func ChildName(l serviceconfig.LoadBalancingConfig) string {
39 return l.(*lbConfig).childBuilder.Name()
40 }
41 42 // ParseConfig parses a child config list and returns a LB config for the
43 // gracefulswitch Balancer.
44 //
45 // cfg is expected to be a json.RawMessage containing a JSON array of LB policy
46 // names + configs as the format of the "loadBalancingConfig" field in
47 // ServiceConfig. It returns a type that should be passed to
48 // UpdateClientConnState in the BalancerConfig field.
49 func ParseConfig(cfg json.RawMessage) (serviceconfig.LoadBalancingConfig, error) {
50 var lbCfg []map[string]json.RawMessage
51 if err := json.Unmarshal(cfg, &lbCfg); err != nil {
52 return nil, err
53 }
54 for i, e := range lbCfg {
55 if len(e) != 1 {
56 return nil, fmt.Errorf("expected a JSON struct with one entry; received entry %v at index %d", e, i)
57 }
58 59 var name string
60 var jsonCfg json.RawMessage
61 for name, jsonCfg = range e {
62 }
63 64 builder := balancer.Get(name)
65 if builder == nil {
66 // Skip unregistered balancer names.
67 continue
68 }
69 70 parser, ok := builder.(balancer.ConfigParser)
71 if !ok {
72 // This is a valid child with no config.
73 return &lbConfig{childBuilder: builder}, nil
74 }
75 76 cfg, err := parser.ParseConfig(jsonCfg)
77 if err != nil {
78 return nil, fmt.Errorf("error parsing config for policy %q: %v", name, err)
79 }
80 return &lbConfig{childBuilder: builder, childConfig: cfg}, nil
81 }
82 83 return nil, fmt.Errorf("no supported policies found in config: %v", string(cfg))
84 }
85