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 = "resolver.example.grpc.io" 36 37 backendAddr = "localhost:50051" 38) 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/name_resolving") 54 } 55} 56 57func main() { 58 passthroughConn, err := grpc.Dial( 59 fmt.Sprintf("passthrough:///%s", backendAddr), // Dial to "passthrough:///localhost:50051" 60 grpc.WithInsecure(), 61 grpc.WithBlock(), 62 ) 63 if err != nil { 64 log.Fatalf("did not connect: %v", err) 65 } 66 defer passthroughConn.Close() 67 68 fmt.Printf("--- calling helloworld.Greeter/SayHello to \"passthrough:///%s\"\n", backendAddr) 69 makeRPCs(passthroughConn, 10) 70 71 fmt.Println() 72 73 exampleConn, err := grpc.Dial( 74 fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName), // Dial to "example:///resolver.example.grpc.io" 75 grpc.WithInsecure(), 76 grpc.WithBlock(), 77 ) 78 if err != nil { 79 log.Fatalf("did not connect: %v", err) 80 } 81 defer exampleConn.Close() 82 83 fmt.Printf("--- calling helloworld.Greeter/SayHello to \"%s:///%s\"\n", exampleScheme, exampleServiceName) 84 makeRPCs(exampleConn, 10) 85} 86 87// Following is an example name resolver. It includes a 88// ResolverBuilder(https://godoc.org/google.golang.org/grpc/resolver#Builder) 89// and a Resolver(https://godoc.org/google.golang.org/grpc/resolver#Resolver). 90// 91// A ResolverBuilder is registered for a scheme (in this example, "example" is 92// the scheme). When a ClientConn is created for this scheme, the 93// ResolverBuilder will be picked to build a Resolver. Note that a new Resolver 94// is built for each ClientConn. The Resolver will watch the updates for the 95// target, and send updates to the ClientConn. 96 97// exampleResolverBuilder is a 98// ResolverBuilder(https://godoc.org/google.golang.org/grpc/resolver#Builder). 99type exampleResolverBuilder struct{} 100 101func (*exampleResolverBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) { 102 r := &exampleResolver{ 103 target: target, 104 cc: cc, 105 addrsStore: map[string][]string{ 106 exampleServiceName: {backendAddr}, 107 }, 108 } 109 r.start() 110 return r, nil 111} 112func (*exampleResolverBuilder) Scheme() string { return exampleScheme } 113 114// exampleResolver is a 115// Resolver(https://godoc.org/google.golang.org/grpc/resolver#Resolver). 116type exampleResolver struct { 117 target resolver.Target 118 cc resolver.ClientConn 119 addrsStore map[string][]string 120} 121 122func (r *exampleResolver) start() { 123 addrStrs := r.addrsStore[r.target.Endpoint] 124 addrs := make([]resolver.Address, len(addrStrs)) 125 for i, s := range addrStrs { 126 addrs[i] = resolver.Address{Addr: s} 127 } 128 r.cc.UpdateState(resolver.State{Addresses: addrs}) 129} 130func (*exampleResolver) ResolveNow(o resolver.ResolveNowOptions) {} 131func (*exampleResolver) Close() {} 132 133func init() { 134 // Register the example ResolverBuilder. This is usually done in a package's 135 // init() function. 136 resolver.Register(&exampleResolverBuilder{}) 137} 138