[Example] Added the deadline example (#35217)

Added the deadline example

Closes #35217

PiperOrigin-RevId: 591074224

examples/cpp/deadline/BUILD

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+# Copyright 2023 the 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.
+
+licenses(["notice"])
+
+cc_binary(
+    name = "client",
+    srcs = ["client.cc"],
+    defines = ["BAZEL_BUILD"],
+    deps = [
+        "//:grpc++",
+        "//examples/protos:helloworld_cc_grpc",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+    ],
+)
+
+cc_binary(
+    name = "server",
+    srcs = ["server.cc"],
+    defines = ["BAZEL_BUILD"],
+    deps = [
+        "//:grpc++",
+        "//examples/protos:helloworld_cc_grpc",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+    ],
+)

examples/cpp/deadline/CMakeLists.txt

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+# Copyright 2023 the 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.
+#
+# Assumes protobuf and gRPC have been installed using cmake.
+# See cmake_externalproject/CMakeLists.txt for all-in-one cmake build
+# that automatically builds all the dependencies before building this example.
+
+cmake_minimum_required(VERSION 3.8)
+
+project(Deadline C CXX)
+
+include(../cmake/common.cmake)
+
+# Proto files
+get_filename_component(hw_proto "../../protos/helloworld.proto" ABSOLUTE)
+get_filename_component(hw_proto_path "${hw_proto}" PATH)
+
+# Generated sources
+set(hw_proto_srcs "${CMAKE_CURRENT_BINARY_DIR}/helloworld.pb.cc")
+set(hw_proto_hdrs "${CMAKE_CURRENT_BINARY_DIR}/helloworld.pb.h")
+set(hw_grpc_srcs "${CMAKE_CURRENT_BINARY_DIR}/helloworld.grpc.pb.cc")
+set(hw_grpc_hdrs "${CMAKE_CURRENT_BINARY_DIR}/helloworld.grpc.pb.h")
+add_custom_command(
+      OUTPUT "${hw_proto_srcs}" "${hw_proto_hdrs}" "${hw_grpc_srcs}" "${hw_grpc_hdrs}"
+      COMMAND ${_PROTOBUF_PROTOC}
+      ARGS --grpc_out "${CMAKE_CURRENT_BINARY_DIR}"
+        --cpp_out "${CMAKE_CURRENT_BINARY_DIR}"
+        -I "${hw_proto_path}"
+        --plugin=protoc-gen-grpc="${_GRPC_CPP_PLUGIN_EXECUTABLE}"
+        "${hw_proto}"
+      DEPENDS "${hw_proto}")
+
+# Include generated *.pb.h files
+include_directories("${CMAKE_CURRENT_BINARY_DIR}")
+
+# hw_grpc_proto
+add_library(hw_grpc_proto
+  ${hw_grpc_srcs}
+  ${hw_grpc_hdrs}
+  ${hw_proto_srcs}
+  ${hw_proto_hdrs})
+target_link_libraries(hw_grpc_proto
+  ${_REFLECTION}
+  ${_GRPC_GRPCPP}
+  ${_PROTOBUF_LIBPROTOBUF})
+
+# Targets greeter_(client|server)
+foreach(_target
+  client server)
+  add_executable(${_target} "${_target}.cc")
+  target_link_libraries(${_target}
+    hw_grpc_proto
+    absl::flags
+    absl::flags_parse
+    absl::strings
+    ${_REFLECTION}
+    ${_GRPC_GRPCPP}
+    ${_PROTOBUF_LIBPROTOBUF})
+endforeach()

examples/cpp/deadline/README.md

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+# Deadline Example
+
+## Overview
+
+This example shows you how to use deadline when calling calls.
+
+### Try it!
+
+Once you have working gRPC, you can build this example using either bazel or cmake.
+
+Run the server, which will listen on port 50051:
+
+```sh
+$ ./server
+```
+
+Run the client (in a different terminal):
+
+```sh
+$ ./client
+```
+
+To simulate the test scenario, the test server implements following functionalities:
+- Response Delay: The server intentionally delays its response for `delay` request messages to induce timeout conditions.
+- Deadline Propagation: Upon receiving a request with the `[propagate me]` prefix, the server forwards it back to itselt.
+  This simulates the propagation of deadlines within the system.
+
+If things go smoothly, you will see the client output:
+
+```
+[Successful request] wanted = 0, got = 0
+[Exceeds deadline] wanted = 4, got = 4
+[Successful request with propagated deadline] wanted = 0, got = 0
+[Exceeds propagated deadline] wanted = 4, got = 4
+```

examples/cpp/deadline/client.cc

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+// Copyright 2023 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.
+
+#include <condition_variable>
+#include <iostream>
+#include <memory>
+#include <mutex>
+#include <string>
+#include <vector>
+
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "absl/strings/str_cat.h"
+
+#include <grpcpp/grpcpp.h>
+
+#ifdef BAZEL_BUILD
+#include "examples/protos/helloworld.grpc.pb.h"
+#else
+#include "helloworld.grpc.pb.h"
+#endif
+
+ABSL_FLAG(std::string, target, "localhost:50051", "Server address");
+
+using grpc::Channel;
+using grpc::ClientContext;
+using grpc::Status;
+using grpc::StatusCode;
+using helloworld::Greeter;
+using helloworld::HelloReply;
+using helloworld::HelloRequest;
+
+void unaryCall(std::shared_ptr<Channel> channel, std::string label,
+               std::string message, grpc::StatusCode expected_code) {
+  std::unique_ptr<Greeter::Stub> stub = Greeter::NewStub(channel);
+
+  // Data we are sending to the server.
+  HelloRequest request;
+  request.set_name(message);
+
+  // Container for the data we expect from the server.
+  HelloReply reply;
+
+  // Context for the client. It could be used to convey extra information to
+  // the server and/or tweak certain RPC behaviors.
+  ClientContext context;
+
+  // Set 1 second timeout
+  context.set_deadline(std::chrono::system_clock::now() +
+                       std::chrono::seconds(1));
+
+  // The actual RPC.
+  std::mutex mu;
+  std::condition_variable cv;
+  bool done = false;
+  Status status;
+  stub->async()->SayHello(&context, &request, &reply,
+                          [&mu, &cv, &done, &status](Status s) {
+                            status = std::move(s);
+                            std::lock_guard<std::mutex> lock(mu);
+                            done = true;
+                            cv.notify_one();
+                          });
+
+  std::unique_lock<std::mutex> lock(mu);
+  while (!done) {
+    cv.wait(lock);
+  }
+
+  // Act upon its status.
+  std::cout << "[" << label << "] wanted = " << expected_code
+            << ", got = " << status.error_code() << std::endl;
+}
+
+int main(int argc, char** argv) {
+  absl::ParseCommandLine(argc, argv);
+  // Instantiate the client. It requires a channel, out of which the actual RPCs
+  // are created. This channel models a connection to an endpoint specified by
+  // the argument "--target=" which is the only expected argument.
+  std::string target_str = absl::GetFlag(FLAGS_target);
+  // We indicate that the channel isn't authenticated (use of
+  // InsecureChannelCredentials()).
+  std::shared_ptr<Channel> channel =
+      grpc::CreateChannel(target_str, grpc::InsecureChannelCredentials());
+  // Making test calls
+  unaryCall(channel, "Successful request", "world", grpc::StatusCode::OK);
+  unaryCall(channel, "Exceeds deadline", "delay",
+            grpc::StatusCode::DEADLINE_EXCEEDED);
+  unaryCall(channel, "Successful request with propagated deadline",
+            "[propagate me]world", grpc::StatusCode::OK);
+  unaryCall(channel, "Exceeds propagated deadline",
+            "[propagate me][propagate me]world",
+            grpc::StatusCode::DEADLINE_EXCEEDED);
+  return 0;
+}

examples/cpp/deadline/server.cc

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+// Copyright 2023 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.
+
+#include <chrono>
+#include <condition_variable>
+#include <iostream>
+#include <memory>
+#include <string>
+#include <thread>
+#include <vector>
+
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "absl/strings/match.h"
+#include "absl/strings/str_format.h"
+
+#include <grpcpp/grpcpp.h>
+
+#ifdef BAZEL_BUILD
+#include "examples/protos/helloworld.grpc.pb.h"
+#else
+#include "helloworld.grpc.pb.h"
+#endif
+
+ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");
+
+using grpc::CallbackServerContext;
+using grpc::Channel;
+using grpc::ClientContext;
+
+using grpc::Server;
+using grpc::ServerBidiReactor;
+using grpc::ServerBuilder;
+using grpc::ServerUnaryReactor;
+using grpc::Status;
+using helloworld::Greeter;
+using helloworld::HelloReply;
+using helloworld::HelloRequest;
+
+// Logic behind the server's behavior.
+class GreeterServiceImpl final : public Greeter::CallbackService {
+ public:
+  GreeterServiceImpl(const std::string& self_address) {
+    self_channel_ =
+        grpc::CreateChannel(self_address, grpc::InsecureChannelCredentials());
+  }
+
+ private:
+  ServerUnaryReactor* SayHello(CallbackServerContext* context,
+                               const HelloRequest* request,
+                               HelloReply* reply) override {
+    if (absl::StartsWith(request->name(), "[propagate me]")) {
+      std::unique_ptr<Greeter::Stub> stub = Greeter::NewStub(self_channel_);
+      std::this_thread::sleep_for(std::chrono::milliseconds(800));
+      // Forwarding this call to the self as a different call
+      HelloRequest new_request;
+      new_request.set_name(request->name().substr(14));
+      std::unique_ptr<ClientContext> new_context =
+          ClientContext::FromCallbackServerContext(*context);
+      std::mutex mu;
+      std::condition_variable cv;
+      bool done = false;
+      Status status;
+      stub->async()->SayHello(new_context.get(), &new_request, reply,
+                              [&mu, &cv, &done, &status](Status s) {
+                                status = std::move(s);
+                                std::lock_guard<std::mutex> lock(mu);
+                                done = true;
+                                cv.notify_one();
+                              });
+      std::unique_lock<std::mutex> lock(mu);
+      while (!done) {
+        cv.wait(lock);
+      }
+      ServerUnaryReactor* reactor = context->DefaultReactor();
+      reactor->Finish(status);
+      return reactor;
+    }
+
+    if (request->name() == "delay") {
+      // Intentionally delay for 1.5 seconds so that
+      // the client will see deadline_exceeded.
+      std::this_thread::sleep_for(std::chrono::milliseconds(1500));
+    }
+
+    reply->set_message(request->name());
+
+    ServerUnaryReactor* reactor = context->DefaultReactor();
+    reactor->Finish(Status::OK);
+    return reactor;
+  }
+
+  std::shared_ptr<Channel> self_channel_;
+};
+
+void RunServer(uint16_t port) {
+  std::string server_address = absl::StrFormat("0.0.0.0:%d", port);
+  GreeterServiceImpl service(server_address);
+
+  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 *synchronous* service.
+  builder.RegisterService(&service);
+  // Finally assemble the server.
+  std::unique_ptr<Server> server(builder.BuildAndStart());
+  std::cout << "Server listening on " << server_address << std::endl;
+
+  // Wait for the server to shutdown. Note that some other thread must be
+  // responsible for shutting down the server for this call to ever return.
+  server->Wait();
+}
+
+int main(int argc, char** argv) {
+  absl::ParseCommandLine(argc, argv);
+  RunServer(absl::GetFlag(FLAGS_port));
+  return 0;
+}