Initial checkin of gRPC to third_party/

third_party/grpc/examples/cpp/helloworld/greeter_async_server.cc

+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <memory>
+#include <iostream>
+#include <string>
+#include <thread>
+
+#include <grpc++/grpc++.h>
+
+#include "helloworld.grpc.pb.h"
+
+using grpc::Server;
+using grpc::ServerAsyncResponseWriter;
+using grpc::ServerBuilder;
+using grpc::ServerContext;
+using grpc::ServerCompletionQueue;
+using grpc::Status;
+using helloworld::HelloRequest;
+using helloworld::HelloReply;
+using helloworld::Greeter;
+
+class ServerImpl final {
+ public:
+  ~ServerImpl() {
+    server_->Shutdown();
+    // Always shutdown the completion queue after the server.
+    cq_->Shutdown();
+  }
+
+  // There is no shutdown handling in this code.
+  void Run() {
+    std::string server_address("0.0.0.0:50051");
+
+    ServerBuilder builder;
+    // Listen on the given address without any authentication mechanism.
+    builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
+    // Register "service_" as the instance through which we'll communicate with
+    // clients. In this case it corresponds to an *asynchronous* service.
+    builder.RegisterService(&service_);
+    // Get hold of the completion queue used for the asynchronous communication
+    // with the gRPC runtime.
+    cq_ = builder.AddCompletionQueue();
+    // Finally assemble the server.
+    server_ = builder.BuildAndStart();
+    std::cout << "Server listening on " << server_address << std::endl;
+
+    // Proceed to the server's main loop.
+    HandleRpcs();
+  }
+
+ private:
+  // Class encompasing the state and logic needed to serve a request.
+  class CallData {
+   public:
+    // Take in the "service" instance (in this case representing an asynchronous
+    // server) and the completion queue "cq" used for asynchronous communication
+    // with the gRPC runtime.
+    CallData(Greeter::AsyncService* service, ServerCompletionQueue* cq)
+        : service_(service), cq_(cq), responder_(&ctx_), status_(CREATE) {
+      // Invoke the serving logic right away.
+      Proceed();
+    }
+
+    void Proceed() {
+      if (status_ == CREATE) {
+        // Make this instance progress to the PROCESS state.
+        status_ = PROCESS;
+
+        // As part of the initial CREATE state, we *request* that the system
+        // start processing SayHello requests. In this request, "this" acts are
+        // the tag uniquely identifying the request (so that different CallData
+        // instances can serve different requests concurrently), in this case
+        // the memory address of this CallData instance.
+        service_->RequestSayHello(&ctx_, &request_, &responder_, cq_, cq_,
+                                  this);
+      } else if (status_ == PROCESS) {
+        // Spawn a new CallData instance to serve new clients while we process
+        // the one for this CallData. The instance will deallocate itself as
+        // part of its FINISH state.
+        new CallData(service_, cq_);
+
+        // The actual processing.
+        std::string prefix("Hello ");
+        reply_.set_message(prefix + request_.name());
+
+        // And we are done! Let the gRPC runtime know we've finished, using the
+        // memory address of this instance as the uniquely identifying tag for
+        // the event.
+        status_ = FINISH;
+        responder_.Finish(reply_, Status::OK, this);
+      } else {
+        GPR_ASSERT(status_ == FINISH);
+        // Once in the FINISH state, deallocate ourselves (CallData).
+        delete this;
+      }
+    }
+
+   private:
+    // The means of communication with the gRPC runtime for an asynchronous
+    // server.
+    Greeter::AsyncService* service_;
+    // The producer-consumer queue where for asynchronous server notifications.
+    ServerCompletionQueue* cq_;
+    // Context for the rpc, allowing to tweak aspects of it such as the use
+    // of compression, authentication, as well as to send metadata back to the
+    // client.
+    ServerContext ctx_;
+
+    // What we get from the client.
+    HelloRequest request_;
+    // What we send back to the client.
+    HelloReply reply_;
+
+    // The means to get back to the client.
+    ServerAsyncResponseWriter<HelloReply> responder_;
+
+    // Let's implement a tiny state machine with the following states.
+    enum CallStatus { CREATE, PROCESS, FINISH };
+    CallStatus status_;  // The current serving state.
+  };
+
+  // This can be run in multiple threads if needed.
+  void HandleRpcs() {
+    // Spawn a new CallData instance to serve new clients.
+    new CallData(&service_, cq_.get());
+    void* tag;  // uniquely identifies a request.
+    bool ok;
+    while (true) {
+      // Block waiting to read the next event from the completion queue. The
+      // event is uniquely identified by its tag, which in this case is the
+      // memory address of a CallData instance.
+      cq_->Next(&tag, &ok);
+      GPR_ASSERT(ok);
+      static_cast<CallData*>(tag)->Proceed();
+    }
+  }
+
+  std::unique_ptr<ServerCompletionQueue> cq_;
+  Greeter::AsyncService service_;
+  std::unique_ptr<Server> server_;
+};
+
+int main(int argc, char** argv) {
+  ServerImpl server;
+  server.Run();
+
+  return 0;
+}