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