e2e-examples/gcs/dummy_server/main.cc

// Copyright 2025 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 <grpcpp/ext/proto_server_reflection_plugin.h>
#include <grpcpp/grpcpp.h>
#include <grpcpp/health_check_service_interface.h>

#include <algorithm>
#include <fstream>
#include <iostream>
#include <memory>
#include <string>

#include "absl/flags/flag.h"
#include "absl/flags/parse.h"
#include "absl/strings/str_format.h"
#include "e2e-examples/gcs/dummy_server/gcs_util.h"
#include "google/storage/v2/storage.grpc.pb.h"

using grpc::CallbackServerContext;
using grpc::Server;
using grpc::ServerBuilder;
using grpc::ServerUnaryReactor;
using grpc::Status;
using grpc::StatusCode;

using ::google::storage::v2::GetObjectRequest;
using ::google::storage::v2::Object;
using ::google::storage::v2::ReadObjectRequest;
using ::google::storage::v2::ReadObjectResponse;
using ::google::storage::v2::StartResumableWriteRequest;
using ::google::storage::v2::StartResumableWriteResponse;
using ::google::storage::v2::WriteObjectRequest;
using ::google::storage::v2::WriteObjectResponse;

ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");
ABSL_FLAG(std::string, cred, "insecure", "Credential type (insecure,ssl,alts)");
ABSL_FLAG(std::string, ssl_key, "", "Path to the server private key file");
ABSL_FLAG(std::string, ssl_cert, "",
          "Path to the server SSL certification chain file");

// Logic and data behind the server's behavior.
class StorageServiceImpl final
    : public google::storage::v2::Storage::CallbackService {
  ServerUnaryReactor* GetObject(CallbackServerContext* context,
                                const GetObjectRequest* request,
                                Object* reply) override {
    Status status;
    const int64_t object_size =
        GcsUtil::GetObjectSize(request->bucket(), request->object());
    if (object_size < 0) {
      status = Status(StatusCode::NOT_FOUND, "Object is not found");
    } else {
      status = Status::OK;
      reply->set_size(object_size);
    }
    ServerUnaryReactor* reactor = context->DefaultReactor();
    reactor->Finish(status);
    return reactor;
  }

  grpc::ServerWriteReactor<ReadObjectResponse>* ReadObject(
      CallbackServerContext* context,
      const ReadObjectRequest* request) override {
    class Reactor : public grpc::ServerWriteReactor<ReadObjectResponse> {
     public:
      Reactor(const ReadObjectRequest* request) {
        const int64_t object_size =
            GcsUtil::GetObjectSize(request->bucket(), request->object());
        if (object_size < 0) {
          Finish(Status(StatusCode::NOT_FOUND, "Object is not found"));
          return;
        }
        left_size_ = object_size;
        if (request->read_limit() > 0) {
          left_size_ = std::min(left_size_, request->read_limit());
        }
        chunk_data_ = absl::Cord(GcsUtil::GetObjectDataChunk(
            google::storage::v2::ServiceConstants::MAX_READ_CHUNK_BYTES));
        MaybeWriteNext();
      }

      void OnWriteDone(bool ok) override {
        if (ok) {
          MaybeWriteNext();
        } else {
          Finish(grpc::Status(grpc::StatusCode::UNKNOWN, "Unexpected failure"));
        }
      }

      void OnDone() override { delete this; }

     private:
      void MaybeWriteNext() {
        if (left_size_ == 0) {
          Finish(grpc::Status::OK);
          return;
        }
        auto data_size =
            std::min(left_size_, static_cast<int64_t>(chunk_data_.size()));
        response_.mutable_checksummed_data()->set_content(
            chunk_data_.Subcord(0, data_size));
        left_size_ -= data_size;
        StartWrite(&response_);
      }

     private:
      int64_t left_size_;
      absl::Cord chunk_data_;
      ReadObjectResponse response_;
    };

    return new Reactor(request);
  }

  grpc::ServerReadReactor<WriteObjectRequest>* WriteObject(
      CallbackServerContext* context, WriteObjectResponse* response) override {
    class Reactor : public grpc::ServerReadReactor<WriteObjectRequest> {
     public:
      explicit Reactor(WriteObjectResponse* response) { StartRead(&request_); }

      void OnReadDone(bool ok) override {
        if (!ok) {
          Finish(grpc::Status::OK);
          return;
        }
        StartRead(&request_);
      }

      void OnDone() override { delete this; }

     private:
      WriteObjectRequest request_;
      WriteObjectResponse* response_ = nullptr;
    };
    return new Reactor(response);
  }
};

static std::string LoadStringFromFile(std::string path) {
  std::ifstream file(path);
  if (!file.is_open()) {
    std::cout << "Failed to open " << path << std::endl;
    abort();
  }
  std::stringstream sstr;
  sstr << file.rdbuf();
  return sstr.str();
}

void RunServer(uint16_t port) {
  std::string server_address = absl::StrFormat("0.0.0.0:%d", port);

  grpc::EnableDefaultHealthCheckService(true);
  grpc::reflection::InitProtoReflectionServerBuilderPlugin();

  ServerBuilder builder;
  const std::string cred = absl::GetFlag(FLAGS_cred);
  if (cred == "insecure") {
    builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
  } else if (cred == "ssl") {
    grpc::SslServerCredentialsOptions::PemKeyCertPair key_cert_pair = {
        LoadStringFromFile(absl::GetFlag(FLAGS_ssl_key)),
        LoadStringFromFile(absl::GetFlag(FLAGS_ssl_cert))};
    grpc::SslServerCredentialsOptions ssl_options;
    ssl_options.pem_key_cert_pairs.emplace_back(key_cert_pair);
    builder.AddListeningPort(server_address,
                             grpc::SslServerCredentials(ssl_options));
  } else if (cred == "alts") {
    grpc::experimental::AltsServerCredentialsOptions alts_opts;
    builder.AddListeningPort(
        server_address, grpc::experimental::AltsServerCredentials(alts_opts));
  } else {
    std::cout << "Unknown cred type: " << cred << std::endl;
    exit(1);
  }

  StorageServiceImpl service;
  builder.RegisterService(&service);

  std::unique_ptr<Server> server(builder.BuildAndStart());
  std::cout << "Server listening on " << server_address << std::endl;

  server->Wait();
}

int main(int argc, char** argv) {
  absl::ParseCommandLine(argc, argv);
  RunServer(absl::GetFlag(FLAGS_port));
  return 0;
}