| /* |
| * |
| * Copyright 2018 gRPC authors. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| */ |
| |
| // Binary client is an example client. |
| package main |
| |
| import ( |
| "context" |
| "fmt" |
| "log" |
| "time" |
| |
| "google.golang.org/grpc" |
| ecpb "google.golang.org/grpc/examples/features/proto/echo" |
| "google.golang.org/grpc/resolver" |
| ) |
| |
| const ( |
| exampleScheme = "example" |
| exampleServiceName = "lb.example.grpc.io" |
| ) |
| |
| var addrs = []string{"localhost:50051", "localhost:50052"} |
| |
| func callUnaryEcho(c ecpb.EchoClient, message string) { |
| ctx, cancel := context.WithTimeout(context.Background(), time.Second) |
| defer cancel() |
| r, err := c.UnaryEcho(ctx, &ecpb.EchoRequest{Message: message}) |
| if err != nil { |
| log.Fatalf("could not greet: %v", err) |
| } |
| fmt.Println(r.Message) |
| } |
| |
| func makeRPCs(cc *grpc.ClientConn, n int) { |
| hwc := ecpb.NewEchoClient(cc) |
| for i := 0; i < n; i++ { |
| callUnaryEcho(hwc, "this is examples/load_balancing") |
| } |
| } |
| |
| func main() { |
| pickfirstConn, err := grpc.Dial( |
| fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName), |
| // grpc.WithBalancerName("pick_first"), // "pick_first" is the default, so this DialOption is not necessary. |
| grpc.WithInsecure(), |
| ) |
| if err != nil { |
| log.Fatalf("did not connect: %v", err) |
| } |
| defer pickfirstConn.Close() |
| |
| fmt.Println("--- calling helloworld.Greeter/SayHello with pick_first ---") |
| makeRPCs(pickfirstConn, 10) |
| |
| fmt.Println() |
| |
| // Make another ClientConn with round_robin policy. |
| roundrobinConn, err := grpc.Dial( |
| fmt.Sprintf("%s:///%s", exampleScheme, exampleServiceName), |
| grpc.WithBalancerName("round_robin"), // This sets the initial balancing policy. |
| grpc.WithInsecure(), |
| ) |
| if err != nil { |
| log.Fatalf("did not connect: %v", err) |
| } |
| defer roundrobinConn.Close() |
| |
| fmt.Println("--- calling helloworld.Greeter/SayHello with round_robin ---") |
| makeRPCs(roundrobinConn, 10) |
| } |
| |
| // Following is an example name resolver implementation. Read the name |
| // resolution example to learn more about it. |
| |
| type exampleResolverBuilder struct{} |
| |
| func (*exampleResolverBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOption) (resolver.Resolver, error) { |
| r := &exampleResolver{ |
| target: target, |
| cc: cc, |
| addrsStore: map[string][]string{ |
| exampleServiceName: addrs, |
| }, |
| } |
| r.start() |
| return r, nil |
| } |
| func (*exampleResolverBuilder) Scheme() string { return exampleScheme } |
| |
| type exampleResolver struct { |
| target resolver.Target |
| cc resolver.ClientConn |
| addrsStore map[string][]string |
| } |
| |
| func (r *exampleResolver) start() { |
| addrStrs := r.addrsStore[r.target.Endpoint] |
| addrs := make([]resolver.Address, len(addrStrs)) |
| for i, s := range addrStrs { |
| addrs[i] = resolver.Address{Addr: s} |
| } |
| r.cc.UpdateState(resolver.State{Addresses: addrs}) |
| } |
| func (*exampleResolver) ResolveNow(o resolver.ResolveNowOption) {} |
| func (*exampleResolver) Close() {} |
| |
| func init() { |
| resolver.Register(&exampleResolverBuilder{}) |
| } |