[Example] Adding error_handling & error_details example (#33129)

Adding a new example showing how to propagate error status from the
server to the client with optional detail information.

examples/cpp/error_details/BUILD

@@ -0,0 +1,45 @@
+# 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 = "greeter_client",
+    srcs = ["greeter_client.cc"],
+    defines = ["BAZEL_BUILD"],
+    deps = [
+        "//:grpc++",
+        "//examples/protos:helloworld_cc_grpc",
+        "//src/proto/grpc/status:status_proto",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+        "@com_google_googleapis//google/rpc:error_details_cc_proto",
+    ],
+)
+
+cc_binary(
+    name = "greeter_server",
+    srcs = ["greeter_server.cc"],
+    defines = ["BAZEL_BUILD"],
+    deps = [
+        "//:grpc++",
+        "//:grpc++_reflection",
+        "//examples/protos:helloworld_cc_grpc",
+        "//src/proto/grpc/status:status_proto",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+        "@com_google_absl//absl/strings:str_format",
+        "@com_google_googleapis//google/rpc:error_details_cc_proto",
+    ],
+)

examples/cpp/error_details/CMakeLists.txt

@@ -0,0 +1,113 @@
+# 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.
+#
+# cmake build file for C++ helloworld example.
+# 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 helloworld.
+
+cmake_minimum_required(VERSION 3.8)
+
+project(ErrorDetails C CXX)
+
+include(../cmake/common.cmake)
+
+# Proto files
+get_filename_component(hw_proto "../../protos/helloworld.proto" ABSOLUTE)
+get_filename_component(hw_proto_path "${hw_proto}" PATH)
+get_filename_component(status_proto "../../../third_party/googleapis/google/rpc/status.proto" ABSOLUTE)
+get_filename_component(status_proto_path "${status_proto}" PATH)
+get_filename_component(error_details_proto "../../../third_party/googleapis/google/rpc/error_details.proto" ABSOLUTE)
+get_filename_component(error_details_proto_path "${error_details_proto}" PATH)
+get_filename_component(protobuf_proto_path "../../../third_party/protobuf/src" ABSOLUTE)
+
+# Generated sources
+set(hw_proto_srcs "${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 "${hw_proto}")
+set(status_proto_srcs "${CMAKE_CURRENT_BINARY_DIR}/status.pb.cc")
+set(status_proto_hdrs "${CMAKE_CURRENT_BINARY_DIR}/status.pb.h")
+add_custom_command(
+      OUTPUT "${status_proto_srcs}" "${status_proto_hdrs}"
+      COMMAND ${_PROTOBUF_PROTOC}
+      ARGS 
+        --cpp_out "${CMAKE_CURRENT_BINARY_DIR}"
+        -I "${status_proto_path}"
+        -I "${protobuf_proto_path}"
+        "${status_proto}"
+      DEPENDS "${status_proto}")      
+set(error_details_proto_srcs "${CMAKE_CURRENT_BINARY_DIR}/error_details.pb.cc")
+set(error_details_proto_hdrs "${CMAKE_CURRENT_BINARY_DIR}/error_details.pb.h")
+add_custom_command(
+      OUTPUT "${error_details_proto_srcs}" "${error_details_proto_hdrs}"
+      COMMAND ${_PROTOBUF_PROTOC}
+      ARGS 
+          --cpp_out "${CMAKE_CURRENT_BINARY_DIR}"
+          -I "${error_details_proto_path}"
+          -I "${protobuf_proto_path}"
+          "${error_details_proto}"
+      DEPENDS "${error_details_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})
+
+# status_proto
+add_library(status_proto
+  ${status_proto_srcs}
+  ${status_proto_hdrs})
+target_link_libraries(status_proto
+  ${_PROTOBUF_LIBPROTOBUF})
+
+# error_details_proto
+add_library(error_details_proto
+  ${error_details_proto_srcs}
+  ${error_details_proto_hdrs})
+target_link_libraries(error_details_proto
+  ${_PROTOBUF_LIBPROTOBUF})
+
+# Targets greeter_(client|server)
+foreach(_target
+  greeter_client greeter_server)
+  add_executable(${_target} "${_target}.cc")
+  target_link_libraries(${_target}
+    hw_grpc_proto
+    status_proto
+    error_details_proto
+    absl::flags
+    absl::flags_parse
+    ${_REFLECTION}
+    ${_GRPC_GRPCPP}
+    ${_PROTOBUF_LIBPROTOBUF})
+endforeach()

examples/cpp/error_details/README.md

@@ -0,0 +1,33 @@
+# Error Details Example
+
+## Overview
+
+This example shows you how to return error with details from the server
+and how to handle it on the client.
+
+### 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
+$ ./greeter_server
+```
+
+Run the client (in a different terminal):
+
+```sh
+$ ./greeter_client
+```
+
+If things go smoothly, you will see the client output:
+
+```
+### Send: SayHello(name=World)
+Ok. ReplyMessage=Hello World
+### Send: SayHello(name=World)
+Failed. Code=8 Message=Request limit exceeded
+Details:
+- Quota: subject=name: World description=Limit one greeting per person
+```

examples/cpp/error_details/greeter_client.cc

@@ -0,0 +1,139 @@
+// 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 "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "absl/strings/str_format.h"
+
+#include <grpcpp/grpcpp.h>
+
+#ifdef BAZEL_BUILD
+#include "examples/protos/helloworld.grpc.pb.h"
+#include "google/rpc/error_details.pb.h"
+
+#include "src/proto/grpc/status/status.pb.h"
+#else
+#include "error_details.pb.h"
+#include "helloworld.grpc.pb.h"
+#include "status.pb.h"
+#endif
+
+ABSL_FLAG(std::string, target, "localhost:50051", "Server address");
+
+using grpc::Channel;
+using grpc::ClientContext;
+using grpc::Status;
+using helloworld::Greeter;
+using helloworld::HelloReply;
+using helloworld::HelloRequest;
+
+class GreeterClient {
+ public:
+  GreeterClient(std::shared_ptr<Channel> channel)
+      : stub_(Greeter::NewStub(channel)) {}
+
+  // Assembles the client's payload, sends it and prints the response back
+  // from the server.
+  void SayHello(const std::string& user) {
+    // Data we are sending to the server.
+    HelloRequest request;
+    request.set_name(user);
+    // 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;
+    // The actual RPC.
+    std::mutex mu;
+    std::condition_variable cv;
+    bool done = false;
+    Status status;
+    std::cout << absl::StrFormat("### Send: SayHello(name=%s)", user)
+              << std::endl;
+    stub_->async()->SayHello(&context, &request, &reply, [&](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);
+    }
+    // Handles the reply
+    if (status.ok()) {
+      std::cout << absl::StrFormat("Ok. ReplyMessage=%s", reply.message())
+                << std::endl;
+    } else {
+      std::cout << absl::StrFormat("Failed. Code=%d Message=%s",
+                                   status.error_code(), status.error_message())
+                << std::endl;
+      PrintErrorDetails(status);
+    }
+  }
+
+  void PrintErrorDetails(grpc::Status status) {
+    auto error_details = status.error_details();
+    if (error_details.empty()) {
+      return;
+    }
+    // If error_details are present in the status, this tries to deserialize
+    // those assuming they're proto messages.
+    google::rpc::Status s;
+    if (!s.ParseFromString(error_details)) {
+      std::cout << "Failed to deserialize `error_details`" << std::endl;
+      return;
+    }
+    std::cout << absl::StrFormat("Details:") << std::endl;
+    for (auto& detail : s.details()) {
+      google::rpc::QuotaFailure quota_failure;
+      if (detail.UnpackTo(&quota_failure)) {
+        for (auto& violation : quota_failure.violations()) {
+          std::cout << absl::StrFormat("- Quota: subject=%s description=%s",
+                                       violation.subject(),
+                                       violation.description())
+                    << std::endl;
+        }
+      } else {
+        std::cout << "Unknown error_detail: " + detail.type_url() << std::endl;
+      }
+    }
+  }
+
+ private:
+  std::unique_ptr<Greeter::Stub> stub_;
+};
+
+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()).
+  GreeterClient greeter(
+      grpc::CreateChannel(target_str, grpc::InsecureChannelCredentials()));
+  // Sends a first new name, expecting OK
+  greeter.SayHello("World");
+  // Sends a duplicate name, expecting RESOURCE_EXHAUSTED with error_details
+  greeter.SayHello("World");
+  return 0;
+}

examples/cpp/error_details/greeter_server.cc

@@ -0,0 +1,117 @@
+// 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 <iostream>
+#include <memory>
+#include <string>
+#include <unordered_set>
+
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "absl/strings/str_format.h"
+#include "absl/synchronization/mutex.h"
+
+#include <grpcpp/ext/proto_server_reflection_plugin.h>
+#include <grpcpp/grpcpp.h>
+#include <grpcpp/health_check_service_interface.h>
+
+#ifdef BAZEL_BUILD
+#include "examples/protos/helloworld.grpc.pb.h"
+#include "google/rpc/error_details.pb.h"
+
+#include "src/proto/grpc/status/status.pb.h"
+#else
+#include "error_details.pb.h"
+#include "helloworld.grpc.pb.h"
+#include "status.pb.h"
+#endif
+
+ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");
+
+using grpc::CallbackServerContext;
+using grpc::Server;
+using grpc::ServerBuilder;
+using grpc::ServerUnaryReactor;
+using grpc::Status;
+using grpc::StatusCode;
+using helloworld::Greeter;
+using helloworld::HelloReply;
+using helloworld::HelloRequest;
+
+// Logic and data behind the server's behavior.
+class GreeterServiceImpl final : public Greeter::CallbackService {
+  ServerUnaryReactor* SayHello(CallbackServerContext* context,
+                               const HelloRequest* request,
+                               HelloReply* reply) override {
+    ServerUnaryReactor* reactor = context->DefaultReactor();
+    Status status;
+    // Checks whether it is a duplicate request
+    if (CheckRequestDuplicate(request->name())) {
+      // Returns an error status with more detailed information.
+      // In this example, the status has additional google::rpc::QuotaFailure
+      // conveying additional information about the error.
+      google::rpc::QuotaFailure quota_failure;
+      auto violation = quota_failure.add_violations();
+      violation->set_subject("name: " + request->name());
+      violation->set_description("Limit one greeting per person");
+      google::rpc::Status s;
+      s.set_code(static_cast<int>(StatusCode::RESOURCE_EXHAUSTED));
+      s.set_message("Request limit exceeded");
+      s.add_details()->PackFrom(quota_failure);
+      status = Status(StatusCode::RESOURCE_EXHAUSTED, "Request limit exceeded",
+                      s.SerializeAsString());
+    } else {
+      reply->set_message(absl::StrFormat("Hello %s", request->name()));
+      status = Status::OK;
+    }
+    reactor->Finish(status);
+    return reactor;
+  }
+
+ private:
+  bool CheckRequestDuplicate(const std::string& name) {
+    absl::MutexLock lock(&mu_);
+    return !request_name_set_.insert(name).second;
+  }
+
+  absl::Mutex mu_;
+  std::unordered_set<std::string> request_name_set_;
+};
+
+void RunServer(uint16_t port) {
+  std::string server_address = absl::StrFormat("0.0.0.0:%d", port);
+  GreeterServiceImpl service;
+
+  grpc::EnableDefaultHealthCheckService(true);
+  grpc::reflection::InitProtoReflectionServerBuilderPlugin();
+  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;
+}

examples/cpp/error_handling/BUILD

@@ -0,0 +1,41 @@
+# 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 = "greeter_client",
+    srcs = ["greeter_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 = "greeter_server",
+    srcs = ["greeter_server.cc"],
+    defines = ["BAZEL_BUILD"],
+    deps = [
+        "//:grpc++",
+        "//:grpc++_reflection",
+        "//examples/protos:helloworld_cc_grpc",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+        "@com_google_absl//absl/strings:str_format",
+    ],
+)

examples/cpp/error_handling/CMakeLists.txt

@@ -0,0 +1,70 @@
+# 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.
+#
+# cmake build file for C++ helloworld example.
+# 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 helloworld.
+
+cmake_minimum_required(VERSION 3.8)
+
+project(ErrorHandling 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}
+  ${_PROTOBUF_LIBPROTOBUF})
+
+# Targets greeter_(client|server)
+foreach(_target
+  greeter_client greeter_server)
+  add_executable(${_target} "${_target}.cc")
+  target_link_libraries(${_target}
+    hw_grpc_proto
+    absl::flags
+    absl::flags_parse
+    ${_REFLECTION}
+    ${_GRPC_GRPCPP}
+    ${_PROTOBUF_LIBPROTOBUF})
+endforeach()

examples/cpp/error_handling/README.md

@@ -0,0 +1,33 @@
+# Error Handling Example
+
+## Overview
+
+This example shows you how to return error from the server and
+how to handle it on the client.
+
+### 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
+$ ./greeter_server
+```
+
+Run the client (in a different terminal):
+
+```sh
+$ ./greeter_client
+```
+
+If things go smoothly, you will see the client output:
+
+```
+### Send: SayHello(name=)
+Failed. Code=3 Message=Length of `Name` should be between 1 and 10
+### Send: SayHello(name=ItsTooLongName)
+Failed. Code=3 Message=Length of `Name` should be between 1 and 10
+### Send: SayHello(name=World)
+Ok. ReplyMessage=Hello World
+```

examples/cpp/error_handling/greeter_client.cc

@@ -0,0 +1,107 @@
+// 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 "absl/flags/flag.h"
+#include "absl/flags/parse.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(std::string, target, "localhost:50051", "Server address");
+
+using grpc::Channel;
+using grpc::ClientContext;
+using grpc::Status;
+using helloworld::Greeter;
+using helloworld::HelloReply;
+using helloworld::HelloRequest;
+
+class GreeterClient {
+ public:
+  GreeterClient(std::shared_ptr<Channel> channel)
+      : stub_(Greeter::NewStub(channel)) {}
+
+  // Assembles the client's payload, sends it and prints the response back
+  // from the server.
+  void SayHello(const std::string& user) {
+    // Data we are sending to the server.
+    HelloRequest request;
+    request.set_name(user);
+    // 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;
+    // The actual RPC.
+    std::mutex mu;
+    std::condition_variable cv;
+    bool done = false;
+    Status status;
+    std::cout << absl::StrFormat("### Send: SayHello(name=%s)", user)
+              << std::endl;
+    stub_->async()->SayHello(&context, &request, &reply, [&](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);
+    }
+    // Handles the reply
+    if (status.ok()) {
+      std::cout << absl::StrFormat("Ok. ReplyMessage=%s", reply.message())
+                << std::endl;
+    } else {
+      std::cout << absl::StrFormat("Failed. Code=%d Message=%s",
+                                   status.error_code(), status.error_message())
+                << std::endl;
+    }
+  }
+
+ private:
+  std::unique_ptr<Greeter::Stub> stub_;
+};
+
+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()).
+  GreeterClient greeter(
+      grpc::CreateChannel(target_str, grpc::InsecureChannelCredentials()));
+  // Sends an empty name, expecting INVALID_ARGUMENT
+  greeter.SayHello("");
+  // Sends a too long name, expecting INVALID_ARGUMENT
+  greeter.SayHello("ItsTooLongName");
+  // Sends a first new name, expecting OK
+  greeter.SayHello("World");
+  return 0;
+}

examples/cpp/error_handling/greeter_server.cc

@@ -0,0 +1,97 @@
+// 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 <iostream>
+#include <memory>
+#include <string>
+#include <unordered_set>
+
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "absl/strings/str_format.h"
+#include "absl/synchronization/mutex.h"
+
+#include <grpcpp/ext/proto_server_reflection_plugin.h>
+#include <grpcpp/grpcpp.h>
+#include <grpcpp/health_check_service_interface.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::Server;
+using grpc::ServerBuilder;
+using grpc::ServerUnaryReactor;
+using grpc::Status;
+using grpc::StatusCode;
+using helloworld::Greeter;
+using helloworld::HelloReply;
+using helloworld::HelloRequest;
+
+// Logic and data behind the server's behavior.
+class GreeterServiceImpl final : public Greeter::CallbackService {
+  ServerUnaryReactor* SayHello(CallbackServerContext* context,
+                               const HelloRequest* request,
+                               HelloReply* reply) override {
+    ServerUnaryReactor* reactor = context->DefaultReactor();
+    Status status;
+    // Checks the length of name
+    if (request->name().empty() || request->name().length() > 10) {
+      // Returns an error status with error code and message.
+      status = Status(StatusCode::INVALID_ARGUMENT,
+                      "Length of `Name` should be between 1 and 10");
+    } else {
+      reply->set_message(absl::StrFormat("Hello %s", request->name()));
+      status = Status::OK;
+    }
+    reactor->Finish(status);
+    return reactor;
+  }
+
+ private:
+  absl::Mutex mu_;
+  std::unordered_set<std::string> request_name_set_;
+};
+
+void RunServer(uint16_t port) {
+  std::string server_address = absl::StrFormat("0.0.0.0:%d", port);
+  GreeterServiceImpl service;
+
+  grpc::EnableDefaultHealthCheckService(true);
+  grpc::reflection::InitProtoReflectionServerBuilderPlugin();
+  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;
+}