1/* 2 * 3 * Copyright 2018 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 an example client. 20package main 21 22import ( 23 "context" 24 "fmt" 25 "log" 26 "time" 27 28 "google.golang.org/grpc" 29 ecpb "google.golang.org/grpc/examples/features/proto/echo" 30 "google.golang.org/grpc/resolver" 31) 32 33const ( 34 exampleScheme = "example" 35 exampleServiceName = "lb.example.grpc.io" 36) 37 38var addrs = []string{"localhost:50051", "localhost:50052"} 39 40func callUnaryEcho(c ecpb.EchoClient, message string) { 41 ctx, cancel := context.WithTimeout(context.Background(), time.Second) 42 defer cancel() 43 r, err := c.UnaryEcho(ctx, &ecpb.EchoRequest{Message: message}) 44 if err != nil { 45 log.Fatalf("could not greet: %v", err) 46 } 47 fmt.Println(r.Message) 48} 49 50func makeRPCs(cc *grpc.ClientConn, n int) { 51 hwc := ecpb.NewEchoClient(cc) 52 for i := 0; i < n; i++ { 53 callUnaryEcho(hwc, "this is examples/load_balancing") 54 } 55} 56 57func main() { 58 pickfirstConn, err := grpc.Dial( 59 fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName), 60 // grpc.WithBalancerName("pick_first"), // "pick_first" is the default, so this DialOption is not necessary. 61 grpc.WithInsecure(), 62 grpc.WithBlock(), 63 ) 64 if err != nil { 65 log.Fatalf("did not connect: %v", err) 66 } 67 defer pickfirstConn.Close() 68 69 fmt.Println("--- calling helloworld.Greeter/SayHello with pick_first ---") 70 makeRPCs(pickfirstConn, 10) 71 72 fmt.Println() 73 74 // Make another ClientConn with round_robin policy. 75 roundrobinConn, err := grpc.Dial( 76 fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName), 77 grpc.WithBalancerName("round_robin"), // This sets the initial balancing policy. 78 grpc.WithInsecure(), 79 grpc.WithBlock(), 80 ) 81 if err != nil { 82 log.Fatalf("did not connect: %v", err) 83 } 84 defer roundrobinConn.Close() 85 86 fmt.Println("--- calling helloworld.Greeter/SayHello with round_robin ---") 87 makeRPCs(roundrobinConn, 10) 88} 89 90// Following is an example name resolver implementation. Read the name 91// resolution example to learn more about it. 92 93type exampleResolverBuilder struct{} 94 95func (*exampleResolverBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) { 96 r := &exampleResolver{ 97 target: target, 98 cc: cc, 99 addrsStore: map[string][]string{ 100 exampleServiceName: addrs, 101 }, 102 } 103 r.start() 104 return r, nil 105} 106func (*exampleResolverBuilder) Scheme() string { return exampleScheme } 107 108type exampleResolver struct { 109 target resolver.Target 110 cc resolver.ClientConn 111 addrsStore map[string][]string 112} 113 114func (r *exampleResolver) start() { 115 addrStrs := r.addrsStore[r.target.Endpoint] 116 addrs := make([]resolver.Address, len(addrStrs)) 117 for i, s := range addrStrs { 118 addrs[i] = resolver.Address{Addr: s} 119 } 120 r.cc.UpdateState(resolver.State{Addresses: addrs}) 121} 122func (*exampleResolver) ResolveNow(o resolver.ResolveNowOptions) {} 123func (*exampleResolver) Close() {} 124 125func init() { 126 resolver.Register(&exampleResolverBuilder{}) 127} 128