largefilesserver.cpp

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

#include <iostream>
#include <memory>
#include <string>

#include "absl/flags/flag.h"
#include "absl/flags/parse.h"
#include "absl/log/initialize.h"
#include "absl/strings/str_format.h"

#include "largefiles.grpc.pb.h"

using grpc::Server;
using grpc::ServerBuilder;
using grpc::ServerContext;
using grpc::Status;
using largefiles::FileWriter;
using largefiles::Chunk;
using largefiles::FileStreamBlock;
using largefiles::FileUploadResponse;

ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");
ABSL_FLAG(size_t, quota, 20, "Resource quota, in megabytes");

// Server reactor that is slow to read incoming messages, causing the buffers
// to fill.
class SlowReadingBidiReactor final
    : public grpc::ServerReadReactor<largefiles::FileStreamBlock> {
 public:
  SlowReadingBidiReactor(largefiles::FileUploadResponse* res)
  : res_(res) { 
    StartRead(&req_);
 }

  void OnReadDone(bool ok) override {
    if (req_.metadata().populated()) {
        std::cout << "Received new file to upload " << req_.metadata().name() << std::endl;
    }
    if (!ok) {
      Finish(grpc::Status::OK);
      return;
    }
    readCount_ += req_.filedata().chunk().size();
    std::cout << "Received file chunk " << req_.filedata().chunk().size() << std::endl;
    usleep(100000); // Simulate slow write to database
    StartRead(&req_);
  }

  void OnDone() override {
    res_->set_readsize(readCount_);
    std::cout << "Uploaded file of total size " << readCount_ << std::endl;
    delete this;
  }

 private:
  largefiles::FileUploadResponse* res_;
  largefiles::FileStreamBlock req_;
  uint64_t readCount_{0};
};

class FileWriterServiceImpl final : public largefiles::FileWriter::CallbackService {
    grpc::ServerReadReactor<largefiles::FileStreamBlock>* UploadFile(grpc::CallbackServerContext* /* context */, ::largefiles::FileUploadResponse* response) override {
        return new SlowReadingBidiReactor(response);
    }
};

void RunServer(uint16_t port) {
  std::string server_address = absl::StrFormat("0.0.0.0:%d", port);
  FileWriterServiceImpl 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);
  grpc::ResourceQuota quota;
  quota.Resize(absl::GetFlag(FLAGS_quota) * 1024 * 1024);

  // 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);
  absl::InitializeLog();
  RunServer(absl::GetFlag(FLAGS_port));
  return 0;
}