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| 1 | +/* |
| 2 | + * |
| 3 | + * Copyright 2025 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 | +// Binary client is a client for the dualstack example. |
| 20 | +package main |
| 21 | + |
| 22 | +import ( |
| 23 | + "context" |
| 24 | + "fmt" |
| 25 | + "log" |
| 26 | + "slices" |
| 27 | + "strings" |
| 28 | + "time" |
| 29 | + |
| 30 | + "google.golang.org/grpc" |
| 31 | + "google.golang.org/grpc/credentials/insecure" |
| 32 | + hwpb "google.golang.org/grpc/examples/helloworld/helloworld" |
| 33 | + "google.golang.org/grpc/peer" |
| 34 | + "google.golang.org/grpc/resolver" |
| 35 | +) |
| 36 | + |
| 37 | +const ( |
| 38 | + port1 = 50051 |
| 39 | + port2 = 50052 |
| 40 | + port3 = 50053 |
| 41 | +) |
| 42 | + |
| 43 | +func init() { |
| 44 | + resolver.Register(&exampleResolver{}) |
| 45 | +} |
| 46 | + |
| 47 | +// exampleResolver implements both, a fake `resolver.Resolver` and |
| 48 | +// `resolver.Builder`. This resolver sends a hard-coded list of 3 endpoints each |
| 49 | +// with 2 addresses (one IPv4 and one IPv6) to the channel. |
| 50 | +type exampleResolver struct{} |
| 51 | + |
| 52 | +func (*exampleResolver) Close() {} |
| 53 | + |
| 54 | +func (*exampleResolver) ResolveNow(resolver.ResolveNowOptions) {} |
| 55 | + |
| 56 | +func (*exampleResolver) Build(_ resolver.Target, cc resolver.ClientConn, _ resolver.BuildOptions) (resolver.Resolver, error) { |
| 57 | + go func() { |
| 58 | + err := cc.UpdateState(resolver.State{ |
| 59 | + Endpoints: []resolver.Endpoint{ |
| 60 | + {Addresses: []resolver.Address{ |
| 61 | + {Addr: fmt.Sprintf("[::1]:%d", port1)}, |
| 62 | + {Addr: fmt.Sprintf("127.0.0.1:%d", port1)}, |
| 63 | + }}, |
| 64 | + {Addresses: []resolver.Address{ |
| 65 | + {Addr: fmt.Sprintf("[::1]:%d", port2)}, |
| 66 | + {Addr: fmt.Sprintf("127.0.0.1:%d", port2)}, |
| 67 | + }}, |
| 68 | + {Addresses: []resolver.Address{ |
| 69 | + {Addr: fmt.Sprintf("[::1]:%d", port3)}, |
| 70 | + {Addr: fmt.Sprintf("127.0.0.1:%d", port3)}, |
| 71 | + }}, |
| 72 | + }, |
| 73 | + }) |
| 74 | + if err != nil { |
| 75 | + log.Fatal("Failed to update resolver state", err) |
| 76 | + } |
| 77 | + }() |
| 78 | + |
| 79 | + return &exampleResolver{}, nil |
| 80 | +} |
| 81 | + |
| 82 | +func (*exampleResolver) Scheme() string { |
| 83 | + return "example" |
| 84 | +} |
| 85 | + |
| 86 | +func main() { |
| 87 | + // First send 5 requests using the default DNS and pickfirst load balancer. |
| 88 | + log.Print("**** Use default DNS resolver ****") |
| 89 | + target := fmt.Sprintf("localhost:%d", port1) |
| 90 | + cc, err := grpc.NewClient(target, grpc.WithTransportCredentials(insecure.NewCredentials())) |
| 91 | + if err != nil { |
| 92 | + log.Fatalf("Failed to create client: %v", err) |
| 93 | + } |
| 94 | + defer cc.Close() |
| 95 | + ctx, cancel := context.WithTimeout(context.Background(), time.Second*10) |
| 96 | + defer cancel() |
| 97 | + client := hwpb.NewGreeterClient(cc) |
| 98 | + |
| 99 | + for i := 0; i < 5; i++ { |
| 100 | + resp, err := client.SayHello(ctx, &hwpb.HelloRequest{ |
| 101 | + Name: fmt.Sprintf("request:%d", i), |
| 102 | + }) |
| 103 | + if err != nil { |
| 104 | + log.Panicf("RPC failed: %v", err) |
| 105 | + } |
| 106 | + log.Print("Greeting:", resp.GetMessage()) |
| 107 | + } |
| 108 | + cc.Close() |
| 109 | + |
| 110 | + log.Print("**** Change to use example name resolver ****") |
| 111 | + dOpts := []grpc.DialOption{ |
| 112 | + grpc.WithTransportCredentials(insecure.NewCredentials()), |
| 113 | + grpc.WithDefaultServiceConfig(`{"loadBalancingConfig": [{"round_robin":{}}]}`), |
| 114 | + } |
| 115 | + cc, err = grpc.NewClient("example:///ignored", dOpts...) |
| 116 | + if err != nil { |
| 117 | + log.Fatalf("Failed to create client: %v", err) |
| 118 | + } |
| 119 | + client = hwpb.NewGreeterClient(cc) |
| 120 | + |
| 121 | + // Send 10 requests using the example nameresolver and round robin load |
| 122 | + // balancer. These requests are evenly distributed among the 3 servers |
| 123 | + // rather than favoring the server listening on both addresses because the |
| 124 | + // resolver groups the 3 servers as 3 endpoints each with 2 addresses. |
| 125 | + if err := waitForDistribution(ctx, client); err != nil { |
| 126 | + log.Panic(err) |
| 127 | + } |
| 128 | + log.Print("Successful multiple iterations of 1:1:1 ratio") |
| 129 | +} |
| 130 | + |
| 131 | +// waitForDistribution makes RPC's on the greeter client until 3 RPC's follow |
| 132 | +// the same 1:1:1 address ratio for the peer. Returns an error if fails to do so |
| 133 | +// before context timeout. |
| 134 | +func waitForDistribution(ctx context.Context, client hwpb.GreeterClient) error { |
| 135 | + wantPeers := []string{ |
| 136 | + // Server 1 is listening on both IPv4 and IPv6 loopback addresses. |
| 137 | + // Since the IPv6 address comes first in the resolver list, it will be |
| 138 | + // given higher priority. |
| 139 | + fmt.Sprintf("[::1]:%d", port1), |
| 140 | + // Server 2 is listening only on the IPv4 loopback address. |
| 141 | + fmt.Sprintf("127.0.0.1:%d", port2), |
| 142 | + // Server 3 is listening only on the IPv6 loopback address. |
| 143 | + fmt.Sprintf("[::1]:%d", port3), |
| 144 | + } |
| 145 | + const iterationsToVerify = 3 |
| 146 | + const backendCount = 3 |
| 147 | + requestCounter := 0 |
| 148 | + |
| 149 | + for ctx.Err() == nil { |
| 150 | + result := make(map[string]int) |
| 151 | + badRatioSeen := false |
| 152 | + for i := 1; i <= iterationsToVerify && !badRatioSeen; i++ { |
| 153 | + for j := 0; j < backendCount; j++ { |
| 154 | + var peer peer.Peer |
| 155 | + resp, err := client.SayHello(ctx, &hwpb.HelloRequest{ |
| 156 | + Name: fmt.Sprintf("request:%d", requestCounter), |
| 157 | + }, grpc.Peer(&peer)) |
| 158 | + requestCounter++ |
| 159 | + if err != nil { |
| 160 | + return fmt.Errorf("RPC failed: %v", err) |
| 161 | + } |
| 162 | + log.Print("Greeting:", resp.GetMessage()) |
| 163 | + |
| 164 | + peerAddr := peer.Addr.String() |
| 165 | + if !slices.Contains(wantPeers, peerAddr) { |
| 166 | + return fmt.Errorf("peer address was not one of %q, got: %v", strings.Join(wantPeers, ", "), peerAddr) |
| 167 | + } |
| 168 | + result[peerAddr]++ |
| 169 | + time.Sleep(time.Millisecond) |
| 170 | + } |
| 171 | + |
| 172 | + // Verify the results of this iteration. |
| 173 | + for _, count := range result { |
| 174 | + if count == i { |
| 175 | + continue |
| 176 | + } |
| 177 | + badRatioSeen = true |
| 178 | + break |
| 179 | + } |
| 180 | + if !badRatioSeen { |
| 181 | + log.Print("Got iteration with 1:1:1 distribution between addresses.") |
| 182 | + } |
| 183 | + } |
| 184 | + if !badRatioSeen { |
| 185 | + return nil |
| 186 | + } |
| 187 | + } |
| 188 | + return fmt.Errorf("timeout waiting for 1:1:1 distribution between addresses %v", wantPeers) |
| 189 | +} |
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