1 /*
2 *
3 * Copyright 2015 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 #include <iostream>
20 #include <memory>
21 #include <string>
22
23 #include <grpcpp/grpcpp.h>
24 #include <grpc/support/log.h>
25 #include <thread>
26
27 #include "helloworld.grpc.pb.h"
28
29 using grpc::Channel;
30 using grpc::ClientAsyncResponseReader;
31 using grpc::ClientContext;
32 using grpc::CompletionQueue;
33 using grpc::Status;
34 using helloworld::HelloRequest;
35 using helloworld::HelloReply;
36 using helloworld::Greeter;
37
38 class GreeterClient {
39 public:
GreeterClient(std::shared_ptr<Channel> channel)40 explicit GreeterClient(std::shared_ptr<Channel> channel)
41 : stub_(Greeter::NewStub(channel)) {}
42
43 // Assembles the client's payload and sends it to the server.
SayHello(const std::string & user)44 void SayHello(const std::string& user) {
45 // Data we are sending to the server.
46 HelloRequest request;
47 request.set_name(user);
48
49 // Call object to store rpc data
50 AsyncClientCall* call = new AsyncClientCall;
51
52 // stub_->PrepareAsyncSayHello() creates an RPC object, returning
53 // an instance to store in "call" but does not actually start the RPC
54 // Because we are using the asynchronous API, we need to hold on to
55 // the "call" instance in order to get updates on the ongoing RPC.
56 call->response_reader =
57 stub_->PrepareAsyncSayHello(&call->context, request, &cq_);
58
59 // StartCall initiates the RPC call
60 call->response_reader->StartCall();
61
62 // Request that, upon completion of the RPC, "reply" be updated with the
63 // server's response; "status" with the indication of whether the operation
64 // was successful. Tag the request with the memory address of the call object.
65 call->response_reader->Finish(&call->reply, &call->status, (void*)call);
66
67 }
68
69 // Loop while listening for completed responses.
70 // Prints out the response from the server.
AsyncCompleteRpc()71 void AsyncCompleteRpc() {
72 void* got_tag;
73 bool ok = false;
74
75 // Block until the next result is available in the completion queue "cq".
76 while (cq_.Next(&got_tag, &ok)) {
77 // The tag in this example is the memory location of the call object
78 AsyncClientCall* call = static_cast<AsyncClientCall*>(got_tag);
79
80 // Verify that the request was completed successfully. Note that "ok"
81 // corresponds solely to the request for updates introduced by Finish().
82 GPR_ASSERT(ok);
83
84 if (call->status.ok())
85 std::cout << "Greeter received: " << call->reply.message() << std::endl;
86 else
87 std::cout << "RPC failed" << std::endl;
88
89 // Once we're complete, deallocate the call object.
90 delete call;
91 }
92 }
93
94 private:
95
96 // struct for keeping state and data information
97 struct AsyncClientCall {
98 // Container for the data we expect from the server.
99 HelloReply reply;
100
101 // Context for the client. It could be used to convey extra information to
102 // the server and/or tweak certain RPC behaviors.
103 ClientContext context;
104
105 // Storage for the status of the RPC upon completion.
106 Status status;
107
108
109 std::unique_ptr<ClientAsyncResponseReader<HelloReply>> response_reader;
110 };
111
112 // Out of the passed in Channel comes the stub, stored here, our view of the
113 // server's exposed services.
114 std::unique_ptr<Greeter::Stub> stub_;
115
116 // The producer-consumer queue we use to communicate asynchronously with the
117 // gRPC runtime.
118 CompletionQueue cq_;
119 };
120
main(int argc,char ** argv)121 int main(int argc, char** argv) {
122
123
124 // Instantiate the client. It requires a channel, out of which the actual RPCs
125 // are created. This channel models a connection to an endpoint (in this case,
126 // localhost at port 50051). We indicate that the channel isn't authenticated
127 // (use of InsecureChannelCredentials()).
128 GreeterClient greeter(grpc::CreateChannel(
129 "localhost:50051", grpc::InsecureChannelCredentials()));
130
131 // Spawn reader thread that loops indefinitely
132 std::thread thread_ = std::thread(&GreeterClient::AsyncCompleteRpc, &greeter);
133
134 for (int i = 0; i < 100; i++) {
135 std::string user("world " + std::to_string(i));
136 greeter.SayHello(user); // The actual RPC call!
137 }
138
139 std::cout << "Press control-c to quit" << std::endl << std::endl;
140 thread_.join(); //blocks forever
141
142 return 0;
143 }
144